text: /*
   * copyright (c) 2001 Fabrice Bellard
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef AVCODEC_AVCODEC_H
  #define AVCODEC_AVCODEC_H
  
  /**
   * @file
   * @ingroup libavc
   * Libavcodec external API header
   */
  
  #include <errno.h>
  #include "libavutil/samplefmt.h"
  #include "libavutil/attributes.h"
  #include "libavutil/avutil.h"
  #include "libavutil/buffer.h"
  #include "libavutil/cpu.h"
  #include "libavutil/channel_layout.h"
  #include "libavutil/dict.h"
  #include "libavutil/frame.h"
  #include "libavutil/hwcontext.h"
  #include "libavutil/log.h"
  #include "libavutil/pixfmt.h"
  #include "libavutil/rational.h"
  
  #include "bsf.h"
  #include "codec.h"
  #include "codec_desc.h"
  #include "codec_par.h"
  #include "codec_id.h"
  #include "packet.h"
  #include "version.h"
  
  /**
   * @defgroup libavc include.libavcodec
   * Encoding/Decoding Library
   *
   * @{
   *
   * @defgroup lavc_decoding Decoding
   * @{
   * @}
   *
   * @defgroup lavc_encoding Encoding
   * @{
   * @}
   *
   * @defgroup lavc_codec Codecs
   * @{
   * @defgroup lavc_codec_native Native Codecs
   * @{
   * @}
   * @defgroup lavc_codec_wrappers External library wrappers
   * @{
   * @}
   * @defgroup lavc_codec_hwaccel Hardware Accelerators bridge
   * @{
   * @}
   * @}
   * @defgroup lavc_internal Internal
   * @{
   * @}
   * @}
   */
  
  /**
   * @ingroup libavc
   * @defgroup lavc_encdec send/receive encoding and decoding API overview
   * @{
   *
   * The avcodec_send_packet()/avcodec_receive_frame()/avcodec_send_frame()/
   * avcodec_receive_packet() functions provide an encode/decode API, which
   * decouples input and output.
   *
   * The API is very similar for encoding/decoding and audio/video, and works as
   * follows:
   * - Set up and open the AVCodecContext as usual.
   * - Send valid input:
   *   - For decoding, call avcodec_send_packet() to give the decoder raw
   *     compressed data in an AVPacket.
   *   - For encoding, call avcodec_send_frame() to give the encoder an AVFrame
   *     containing uncompressed audio or video.
   *
   *   In both cases, it is recommended that AVPackets and AVFrames are
   *   refcounted, or include.libavcodec might have to copy the input data. (include.libavformat
   *   always returns refcounted AVPackets, and av_frame_get_buffer() allocates
   *   refcounted AVFrames.)
   * - Receive output in a loop. Periodically call one of the avcodec_receive_*()
   *   functions and process their output:
   *   - For decoding, call avcodec_receive_frame(). On success, it will return
   *     an AVFrame containing uncompressed audio or video data.
   *   - For encoding, call avcodec_receive_packet(). On success, it will return
   *     an AVPacket with a compressed frame.
   *
   *   Repeat this call until it returns AVERROR(EAGAIN) or an error. The
   *   AVERROR(EAGAIN) return value means that new input data is required to
   *   return new output. In this case, continue with sending input. For each
   *   input frame/packet, the codec will typically return 1 output frame/packet,
   *   but it can also be 0 or more than 1.
   *
   * At the beginning of decoding or encoding, the codec might accept multiple
   * input frames/packets without returning a frame, until its internal buffers
   * are filled. This situation is handled transparently if you follow the steps
   * outlined above.
   *
   * In theory, sending input can result in EAGAIN - this should happen only if
   * not all output was received. You can use this to structure alternative decode
   * or encode loops other than the one suggested above. For example, you could
   * try sending new input on each iteration, and try to receive output if that
   * returns EAGAIN.
   *
   * End of stream situations. These require "flushing" (aka draining) the codec,
   * as the codec might buffer multiple frames or packets internally for
   * performance or out of necessity (consider B-frames).
   * This is handled as follows:
   * - Instead of valid input, send NULL to the avcodec_send_packet() (decoding)
   *   or avcodec_send_frame() (encoding) functions. This will enter draining
   *   mode.
   * - Call avcodec_receive_frame() (decoding) or avcodec_receive_packet()
   *   (encoding) in a loop until AVERROR_EOF is returned. The functions will
   *   not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
   * - Before decoding can be resumed again, the codec has to be reset with
   *   avcodec_flush_buffers().
   *
   * Using the API as outlined above is highly recommended. But it is also
   * possible to call functions outside of this rigid schema. For example, you can
   * call avcodec_send_packet() repeatedly without calling
   * avcodec_receive_frame(). In this case, avcodec_send_packet() will succeed
   * until the codec's internal buffer has been filled up (which is typically of
   * size 1 per output frame, after initial input), and then reject input with
   * AVERROR(EAGAIN). Once it starts rejecting input, you have no choice but to
   * read at least some output.
   *
   * Not all codecs will follow a rigid and predictable dataflow; the only
   * guarantee is that an AVERROR(EAGAIN) return value on a send/receive call on
   * one end implies that a receive/send call on the other end will succeed, or
   * at least will not fail with AVERROR(EAGAIN). In general, no codec will
   * permit unlimited buffering of input or output.
   *
   * This API replaces the following legacy functions:
   * - avcodec_decode_video2() and avcodec_decode_audio4():
   *   Use avcodec_send_packet() to feed input to the decoder, then use
   *   avcodec_receive_frame() to receive decoded frames after each packet.
   *   Unlike with the old video decoding API, multiple frames might result from
   *   a packet. For audio, splitting the input packet into frames by partially
   *   decoding packets becomes transparent to the API user. You never need to
   *   feed an AVPacket to the API twice (unless it is rejected with AVERROR(EAGAIN) - then
   *   no data was read from the packet).
   *   Additionally, sending a flush/draining packet is required only once.
   * - avcodec_encode_video2()/avcodec_encode_audio2():
   *   Use avcodec_send_frame() to feed input to the encoder, then use
   *   avcodec_receive_packet() to receive encoded packets.
   *   Providing user-allocated buffers for avcodec_receive_packet() is not
   *   possible.
   * - The new API does not handle subtitles yet.
   *
   * Mixing new and old function calls on the same AVCodecContext is not allowed,
   * and will result in undefined behavior.
   *
   * Some codecs might require using the new API; using the old API will return
   * an error when calling it. All codecs support the new API.
   *
   * A codec is not allowed to return AVERROR(EAGAIN) for both sending and receiving. This
   * would be an invalid state, which could put the codec user into an endless
   * loop. The API has no concept of time either: it cannot happen that trying to
   * do avcodec_send_packet() results in AVERROR(EAGAIN), but a repeated call 1 second
   * later accepts the packet (with no other receive/flush API calls involved).
   * The API is a strict state machine, and the passage of time is not supposed
   * to influence it. Some timing-dependent behavior might still be deemed
   * acceptable in certain cases. But it must never result in both send/receive
   * returning EAGAIN at the same time at any point. It must also absolutely be
   * avoided that the current state is "unstable" and can "flip-flop" between
   * the send/receive APIs allowing progress. For example, it's not allowed that
   * the codec randomly decides that it actually wants to consume a packet now
   * instead of returning a frame, after it just returned AVERROR(EAGAIN) on an
   * avcodec_send_packet() call.
   * @}
   */
  
  /**
   * @defgroup lavc_core Core functions/structures.
   * @ingroup libavc
   *
   * Basic definitions, functions for querying include.libavcodec capabilities,
   * allocating core structures, etc.
   * @{
   */
  
  /**
   * @ingroup lavc_decoding
   * Required number of additionally allocated bytes at the end of the input bitstream for decoding.
   * This is mainly needed because some optimized bitstream readers read
   * 32 or 64 bit at once and could read over the end.<br>
   * Note: If the first 23 bits of the additional bytes are not 0, then damaged
   * MPEG bitstreams could cause overread and segfault.
   */
  #define AV_INPUT_BUFFER_PADDING_SIZE 64
  
  /**
   * @ingroup lavc_encoding
   * minimum encoding buffer size
   * Used to avoid some checks during header writing.
   */
  #define AV_INPUT_BUFFER_MIN_SIZE 16384
  
  /**
   * @ingroup lavc_decoding
   */
  enum AVDiscard{
      /* We leave some space between them for extensions (drop some
       * keyframes for intra-only or drop just some bidir frames). */
      AVDISCARD_NONE    =-16, ///< discard nothing
      AVDISCARD_DEFAULT =  0, ///< discard useless packets like 0 size packets in avi
      AVDISCARD_NONREF  =  8, ///< discard all non reference
      AVDISCARD_BIDIR   = 16, ///< discard all bidirectional frames
      AVDISCARD_NONINTRA= 24, ///< discard all non intra frames
      AVDISCARD_NONKEY  = 32, ///< discard all frames except keyframes
      AVDISCARD_ALL     = 48, ///< discard all
  };
  
  enum AVAudioServiceType {
      AV_AUDIO_SERVICE_TYPE_MAIN              = 0,
      AV_AUDIO_SERVICE_TYPE_EFFECTS           = 1,
      AV_AUDIO_SERVICE_TYPE_VISUALLY_IMPAIRED = 2,
      AV_AUDIO_SERVICE_TYPE_HEARING_IMPAIRED  = 3,
      AV_AUDIO_SERVICE_TYPE_DIALOGUE          = 4,
      AV_AUDIO_SERVICE_TYPE_COMMENTARY        = 5,
      AV_AUDIO_SERVICE_TYPE_EMERGENCY         = 6,
      AV_AUDIO_SERVICE_TYPE_VOICE_OVER        = 7,
      AV_AUDIO_SERVICE_TYPE_KARAOKE           = 8,
      AV_AUDIO_SERVICE_TYPE_NB                   , ///< Not part of ABI
  };
  
  /**
   * @ingroup lavc_encoding
   */
  typedef struct RcOverride{
      int start_frame;
      int end_frame;
      int qscale; // If this is 0 then quality_factor will be used instead.
      float quality_factor;
  } RcOverride;
  
  /* encoding support
     These flags can be passed in AVCodecContext.flags before initialization.
     Note: Not everything is supported yet.
  */
  
  /**
   * Allow decoders to produce frames with data planes that are not aligned
   * to CPU requirements (e.g. due to cropping).
   */
  #define AV_CODEC_FLAG_UNALIGNED       (1 <<  0)
  /**
   * Use fixed qscale.
   */
  #define AV_CODEC_FLAG_QSCALE          (1 <<  1)
  /**
   * 4 MV per MB allowed / advanced prediction for H.263.
   */
  #define AV_CODEC_FLAG_4MV             (1 <<  2)
  /**
   * Output even those frames that might be corrupted.
   */
  #define AV_CODEC_FLAG_OUTPUT_CORRUPT  (1 <<  3)
  /**
   * Use qpel MC.
   */
  #define AV_CODEC_FLAG_QPEL            (1 <<  4)
  /**
   * Don't output frames whose parameters differ from first
   * decoded frame in stream.
   */
  #define AV_CODEC_FLAG_DROPCHANGED     (1 <<  5)
  /**
   * Use internal 2pass ratecontrol in first pass mode.
   */
  #define AV_CODEC_FLAG_PASS1           (1 <<  9)
  /**
   * Use internal 2pass ratecontrol in second pass mode.
   */
  #define AV_CODEC_FLAG_PASS2           (1 << 10)
  /**
   * loop filter.
   */
  #define AV_CODEC_FLAG_LOOP_FILTER     (1 << 11)
  /**
   * Only decode/encode grayscale.
   */
  #define AV_CODEC_FLAG_GRAY            (1 << 13)
  /**
   * error[?] variables will be set during encoding.
   */
  #define AV_CODEC_FLAG_PSNR            (1 << 15)
  /**
   * Input bitstream might be truncated at a random location
   * instead of only at frame boundaries.
   */
  #define AV_CODEC_FLAG_TRUNCATED       (1 << 16)
  /**
   * Use interlaced DCT.
   */
  #define AV_CODEC_FLAG_INTERLACED_DCT  (1 << 18)
  /**
   * Force low delay.
   */
  #define AV_CODEC_FLAG_LOW_DELAY       (1 << 19)
  /**
   * Place global headers in extradata instead of every keyframe.
   */
  #define AV_CODEC_FLAG_GLOBAL_HEADER   (1 << 22)
  /**
   * Use only bitexact stuff (except (I)DCT).
   */
  #define AV_CODEC_FLAG_BITEXACT        (1 << 23)
  /* Fx : Flag for H.263+ extra options */
  /**
   * H.263 advanced intra coding / MPEG-4 AC prediction
   */
  #define AV_CODEC_FLAG_AC_PRED         (1 << 24)
  /**
   * interlaced motion estimation
   */
  #define AV_CODEC_FLAG_INTERLACED_ME   (1 << 29)
  #define AV_CODEC_FLAG_CLOSED_GOP      (1U << 31)
  
  /**
   * Allow non spec compliant speedup tricks.
   */
  #define AV_CODEC_FLAG2_FAST           (1 <<  0)
  /**
   * Skip bitstream encoding.
   */
  #define AV_CODEC_FLAG2_NO_OUTPUT      (1 <<  2)
  /**
   * Place global headers at every keyframe instead of in extradata.
   */
  #define AV_CODEC_FLAG2_LOCAL_HEADER   (1 <<  3)
  
  /**
   * timecode is in drop frame format. DEPRECATED!!!!
   */
  #define AV_CODEC_FLAG2_DROP_FRAME_TIMECODE (1 << 13)
  
  /**
   * Input bitstream might be truncated at a packet boundaries
   * instead of only at frame boundaries.
   */
  #define AV_CODEC_FLAG2_CHUNKS         (1 << 15)
  /**
   * Discard cropping information from SPS.
   */
  #define AV_CODEC_FLAG2_IGNORE_CROP    (1 << 16)
  
  /**
   * Show all frames before the first keyframe
   */
  #define AV_CODEC_FLAG2_SHOW_ALL       (1 << 22)
  /**
   * Export motion vectors through frame side data
   */
  #define AV_CODEC_FLAG2_EXPORT_MVS     (1 << 28)
  /**
   * Do not skip samples and export skip information as frame side data
   */
  #define AV_CODEC_FLAG2_SKIP_MANUAL    (1 << 29)
  /**
   * Do not reset ASS ReadOrder field on flush (subtitles decoding)
   */
  #define AV_CODEC_FLAG2_RO_FLUSH_NOOP  (1 << 30)
  
  /* Unsupported options :
   *              Syntax Arithmetic coding (SAC)
   *              Reference Picture Selection
   *              Independent Segment Decoding */
  /* /Fx */
  /* codec capabilities */
  
  /* Exported side data.
     These flags can be passed in AVCodecContext.export_side_data before initialization.
  */
  /**
   * Export motion vectors through frame side data
   */
  #define AV_CODEC_EXPORT_DATA_MVS         (1 << 0)
  /**
   * Export encoder Producer Reference Time through packet side data
   */
  #define AV_CODEC_EXPORT_DATA_PRFT        (1 << 1)
  /**
   * Decoding only.
   * Export the AVVideoEncParams structure through frame side data.
   */
  #define AV_CODEC_EXPORT_DATA_VIDEO_ENC_PARAMS (1 << 2)
  /**
   * Decoding only.
   * Do not apply film grain, export it instead.
   */
  #define AV_CODEC_EXPORT_DATA_FILM_GRAIN (1 << 3)
  
  /**
   * Pan Scan area.
   * This specifies the area which should be displayed.
   * Note there may be multiple such areas for one frame.
   */
  typedef struct AVPanScan {
      /**
       * id
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
      int id;
  
      /**
       * width and height in 1/16 pel
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
      int width;
      int height;
  
      /**
       * position of the top left corner in 1/16 pel for up to 3 fields/frames
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
      int16_t position[3][2];
  } AVPanScan;
  
  /**
   * This structure describes the bitrate properties of an encoded bitstream. It
   * roughly corresponds to a subset the VBV parameters for MPEG-2 or HRD
   * parameters for H.264/HEVC.
   */
  typedef struct AVCPBProperties {
      /**
       * Maximum bitrate of the stream, in bits per second.
       * Zero if unknown or unspecified.
       */
  #if FF_API_UNSANITIZED_BITRATES
      int max_bitrate;
  #else
      int64_t max_bitrate;
  #endif
      /**
       * Minimum bitrate of the stream, in bits per second.
       * Zero if unknown or unspecified.
       */
  #if FF_API_UNSANITIZED_BITRATES
      int min_bitrate;
  #else
      int64_t min_bitrate;
  #endif
      /**
       * Average bitrate of the stream, in bits per second.
       * Zero if unknown or unspecified.
       */
  #if FF_API_UNSANITIZED_BITRATES
      int avg_bitrate;
  #else
      int64_t avg_bitrate;
  #endif
  
      /**
       * The size of the buffer to which the ratecontrol is applied, in bits.
       * Zero if unknown or unspecified.
       */
      int buffer_size;
  
      /**
       * The delay between the time the packet this structure is associated with
       * is received and the time when it should be decoded, in periods of a 27MHz
       * clock.
       *
       * UINT64_MAX when unknown or unspecified.
       */
      uint64_t vbv_delay;
  } AVCPBProperties;
  
  /**
   * This structure supplies correlation between a packet timestamp and a wall clock
   * production time. The definition follows the Producer Reference Time ('prft')
   * as defined in ISO/IEC 14496-12
   */
  typedef struct AVProducerReferenceTime {
      /**
       * A UTC timestamp, in microseconds, since Unix epoch (e.g, av_gettime()).
       */
      int64_t wallclock;
      int flags;
  } AVProducerReferenceTime;
  
  /**
   * The decoder will keep a reference to the frame and may reuse it later.
   */
  #define AV_GET_BUFFER_FLAG_REF (1 << 0)
  
  /**
   * The encoder will keep a reference to the packet and may reuse it later.
   */
  #define AV_GET_ENCODE_BUFFER_FLAG_REF (1 << 0)
  
  struct AVCodecInternal;
  
  /**
   * main external API structure.
   * New fields can be added to the end with minor version bumps.
   * Removal, reordering and changes to existing fields require a major
   * version bump.
   * You can use AVOptions (av_opt* / av_set/get*()) to access these fields from user
   * applications.
   * The name string for AVOptions options matches the associated command line
   * parameter name and can be found in include.libavcodec/options_table.h
   * The AVOption/command line parameter names differ in some cases from the C
   * structure field names for historic reasons or brevity.
   * sizeof(AVCodecContext) must not be used outside libav*.
   */
  typedef struct AVCodecContext {
      /**
       * information on struct for av_log
       * - set by avcodec_alloc_context3
       */
      const AVClass *av_class;
      int log_level_offset;
  
      enum AVMediaType codec_type; /* see AVMEDIA_TYPE_xxx */
      const struct AVCodec  *codec;
      enum AVCodecID     codec_id; /* see AV_CODEC_ID_xxx */
  
      /**
       * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
       * This is used to work around some encoder bugs.
       * A demuxer should set this to what is stored in the field used to identify the codec.
       * If there are multiple such fields in a container then the demuxer should choose the one
       * which maximizes the information about the used codec.
       * If the codec tag field in a container is larger than 32 bits then the demuxer should
       * remap the longer ID to 32 bits with a table or other structure. Alternatively a new
       * extra_codec_tag + size could be added but for this a clear advantage must be demonstrated
       * first.
       * - encoding: Set by user, if not then the default based on codec_id will be used.
       * - decoding: Set by user, will be converted to uppercase by include.libavcodec during init.
       */
      unsigned int codec_tag;
  
      void *priv_data;
  
      /**
       * Private context used for internal data.
       *
       * Unlike priv_data, this is not codec-specific. It is used in general
       * include.libavcodec functions.
       */
      struct AVCodecInternal *internal;
  
      /**
       * Private data of the user, can be used to carry app specific stuff.
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      void *opaque;
  
      /**
       * the average bitrate
       * - encoding: Set by user; unused for constant quantizer encoding.
       * - decoding: Set by user, may be overwritten by include.libavcodec
       *             if this info is available in the stream
       */
      int64_t bit_rate;
  
      /**
       * number of bits the bitstream is allowed to diverge from the reference.
       *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
       * - encoding: Set by user; unused for constant quantizer encoding.
       * - decoding: unused
       */
      int bit_rate_tolerance;
  
      /**
       * Global quality for codecs which cannot change it per frame.
       * This should be proportional to MPEG-1/2/4 qscale.
       * - encoding: Set by user.
       * - decoding: unused
       */
      int global_quality;
  
      /**
       * - encoding: Set by user.
       * - decoding: unused
       */
      int compression_level;
  #define FF_COMPRESSION_DEFAULT -1
  
      /**
       * AV_CODEC_FLAG_*.
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      int flags;
  
      /**
       * AV_CODEC_FLAG2_*
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      int flags2;
  
      /**
       * some codecs need / can use extradata like Huffman tables.
       * MJPEG: Huffman tables
       * rv10: additional flags
       * MPEG-4: global headers (they can be in the bitstream or here)
       * The allocated memory should be AV_INPUT_BUFFER_PADDING_SIZE bytes larger
       * than extradata_size to avoid problems if it is read with the bitstream reader.
       * The bytewise contents of extradata must not depend on the architecture or CPU endianness.
       * Must be allocated with the av_malloc() family of functions.
       * - encoding: Set/allocated/freed by include.libavcodec.
       * - decoding: Set/allocated/freed by user.
       */
      uint8_t *extradata;
      int extradata_size;
  
      /**
       * This is the fundamental unit of time (in seconds) in terms
       * of which frame timestamps are represented. For fixed-fps content,
       * timebase should be 1/framerate and timestamp increments should be
       * identically 1.
       * This often, but not always is the inverse of the frame rate or field rate
       * for video. 1/time_base is not the average frame rate if the frame rate is not
       * constant.
       *
       * Like containers, elementary streams also can store timestamps, 1/time_base
       * is the unit in which these timestamps are specified.
       * As example of such codec time base see ISO/IEC 14496-2:2001(E)
       * vop_time_increment_resolution and fixed_vop_rate
       * (fixed_vop_rate == 0 implies that it is different from the framerate)
       *
       * - encoding: MUST be set by user.
       * - decoding: the use of this field for decoding is deprecated.
       *             Use framerate instead.
       */
      AVRational time_base;
  
      /**
       * For some codecs, the time base is closer to the field rate than the frame rate.
       * Most notably, H.264 and MPEG-2 specify time_base as half of frame duration
       * if no telecine is used ...
       *
       * Set to time_base ticks per frame. Default 1, e.g., H.264/MPEG-2 set it to 2.
       */
      int ticks_per_frame;
  
      /**
       * Codec delay.
       *
       * Encoding: Number of frames delay there will be from the encoder input to
       *           the decoder output. (we assume the decoder matches the spec)
       * Decoding: Number of frames delay in addition to what a standard decoder
       *           as specified in the spec would produce.
       *
       * Video:
       *   Number of frames the decoded output will be delayed relative to the
       *   encoded input.
       *
       * Audio:
       *   For encoding, this field is unused (see initial_padding).
       *
       *   For decoding, this is the number of samples the decoder needs to
       *   output before the decoder's output is valid. When seeking, you should
       *   start decoding this many samples prior to your desired seek point.
       *
       * - encoding: Set by include.libavcodec.
       * - decoding: Set by include.libavcodec.
       */
      int delay;
  
  
      /* video only */
      /**
       * picture width / height.
       *
       * @note Those fields may not match the values of the last
       * AVFrame output by avcodec_decode_video2 due frame
       * reordering.
       *
       * - encoding: MUST be set by user.
       * - decoding: May be set by the user before opening the decoder if known e.g.
       *             from the container. Some decoders will require the dimensions
       *             to be set by the caller. During decoding, the decoder may
       *             overwrite those values as required while parsing the data.
       */
      int width, height;
  
      /**
       * Bitstream width / height, may be different from width/height e.g. when
       * the decoded frame is cropped before being output or lowres is enabled.
       *
       * @note Those field may not match the value of the last
       * AVFrame output by avcodec_receive_frame() due frame
       * reordering.
       *
       * - encoding: unused
       * - decoding: May be set by the user before opening the decoder if known
       *             e.g. from the container. During decoding, the decoder may
       *             overwrite those values as required while parsing the data.
       */
      int coded_width, coded_height;
  
      /**
       * the number of pictures in a group of pictures, or 0 for intra_only
       * - encoding: Set by user.
       * - decoding: unused
       */
      int gop_size;
  
      /**
       * Pixel format, see AV_PIX_FMT_xxx.
       * May be set by the demuxer if known from headers.
       * May be overridden by the decoder if it knows better.
       *
       * @note This field may not match the value of the last
       * AVFrame output by avcodec_receive_frame() due frame
       * reordering.
       *
       * - encoding: Set by user.
       * - decoding: Set by user if known, overridden by include.libavcodec while
       *             parsing the data.
       */
      enum AVPixelFormat pix_fmt;
  
      /**
       * If non NULL, 'draw_horiz_band' is called by the include.libavcodec
       * decoder to draw a horizontal band. It improves cache usage. Not
       * all codecs can do that. You must check the codec capabilities
       * beforehand.
       * When multithreading is used, it may be called from multiple threads
       * at the same time; threads might draw different parts of the same AVFrame,
       * or multiple AVFrames, and there is no guarantee that slices will be drawn
       * in order.
       * The function is also used by hardware acceleration APIs.
       * It is called at least once during frame decoding to pass
       * the data needed for hardware render.
       * In that mode instead of pixel data, AVFrame points to
       * a structure specific to the acceleration API. The application
       * reads the structure and can change some fields to indicate progress
       * or mark state.
       * - encoding: unused
       * - decoding: Set by user.
       * @param height the height of the slice
       * @param y the y position of the slice
       * @param type 1->top field, 2->bottom field, 3->frame
       * @param offset offset into the AVFrame.data from which the slice should be read
       */
      void (*draw_horiz_band)(struct AVCodecContext *s,
                              const AVFrame *src, int offset[AV_NUM_DATA_POINTERS],
                              int y, int type, int height);
  
      /**
       * callback to negotiate the pixelFormat
       * @param fmt is the list of formats which are supported by the codec,
       * it is terminated by -1 as 0 is a valid format, the formats are ordered by quality.
       * The first is always the native one.
       * @note The callback may be called again immediately if initialization for
       * the selected (hardware-accelerated) pixel format failed.
       * @warning Behavior is undefined if the callback returns a value not
       * in the fmt list of formats.
       * @return the chosen format
       * - encoding: unused
       * - decoding: Set by user, if not set the native format will be chosen.
       */
      enum AVPixelFormat (*get_format)(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
  
      /**
       * maximum number of B-frames between non-B-frames
       * Note: The output will be delayed by max_b_frames+1 relative to the input.
       * - encoding: Set by user.
       * - decoding: unused
       */
      int max_b_frames;
  
      /**
       * qscale factor between IP and B-frames
       * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
       * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
       * - encoding: Set by user.
       * - decoding: unused
       */
      float b_quant_factor;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int b_frame_strategy;
  #endif
  
      /**
       * qscale offset between IP and B-frames
       * - encoding: Set by user.
       * - decoding: unused
       */
      float b_quant_offset;
  
      /**
       * Size of the frame reordering buffer in the decoder.
       * For MPEG-2 it is 1 IPB or 0 low delay IP.
       * - encoding: Set by include.libavcodec.
       * - decoding: Set by include.libavcodec.
       */
      int has_b_frames;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int mpeg_quant;
  #endif
  
      /**
       * qscale factor between P- and I-frames
       * If > 0 then the last P-frame quantizer will be used (q = lastp_q * factor + offset).
       * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
       * - encoding: Set by user.
       * - decoding: unused
       */
      float i_quant_factor;
  
      /**
       * qscale offset between P and I-frames
       * - encoding: Set by user.
       * - decoding: unused
       */
      float i_quant_offset;
  
      /**
       * luminance masking (0-> disabled)
       * - encoding: Set by user.
       * - decoding: unused
       */
      float lumi_masking;
  
      /**
       * temporary complexity masking (0-> disabled)
       * - encoding: Set by user.
       * - decoding: unused
       */
      float temporal_cplx_masking;
  
      /**
       * spatial complexity masking (0-> disabled)
       * - encoding: Set by user.
       * - decoding: unused
       */
      float spatial_cplx_masking;
  
      /**
       * p block masking (0-> disabled)
       * - encoding: Set by user.
       * - decoding: unused
       */
      float p_masking;
  
      /**
       * darkness masking (0-> disabled)
       * - encoding: Set by user.
       * - decoding: unused
       */
      float dark_masking;
  
      /**
       * slice count
       * - encoding: Set by include.libavcodec.
       * - decoding: Set by user (or 0).
       */
      int slice_count;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
       int prediction_method;
  #define FF_PRED_LEFT   0
  #define FF_PRED_PLANE  1
  #define FF_PRED_MEDIAN 2
  #endif
  
      /**
       * slice offsets in the frame in bytes
       * - encoding: Set/allocated by include.libavcodec.
       * - decoding: Set/allocated by user (or NULL).
       */
      int *slice_offset;
  
      /**
       * sample aspect ratio (0 if unknown)
       * That is the width of a pixel divided by the height of the pixel.
       * Numerator and denominator must be relatively prime and smaller than 256 for some video standards.
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
      AVRational sample_aspect_ratio;
  
      /**
       * motion estimation comparison function
       * - encoding: Set by user.
       * - decoding: unused
       */
      int me_cmp;
      /**
       * subpixel motion estimation comparison function
       * - encoding: Set by user.
       * - decoding: unused
       */
      int me_sub_cmp;
      /**
       * macroblock comparison function (not supported yet)
       * - encoding: Set by user.
       * - decoding: unused
       */
      int mb_cmp;
      /**
       * interlaced DCT comparison function
       * - encoding: Set by user.
       * - decoding: unused
       */
      int ildct_cmp;
  #define FF_CMP_SAD          0
  #define FF_CMP_SSE          1
  #define FF_CMP_SATD         2
  #define FF_CMP_DCT          3
  #define FF_CMP_PSNR         4
  #define FF_CMP_BIT          5
  #define FF_CMP_RD           6
  #define FF_CMP_ZERO         7
  #define FF_CMP_VSAD         8
  #define FF_CMP_VSSE         9
  #define FF_CMP_NSSE         10
  #define FF_CMP_W53          11
  #define FF_CMP_W97          12
  #define FF_CMP_DCTMAX       13
  #define FF_CMP_DCT264       14
  #define FF_CMP_MEDIAN_SAD   15
  #define FF_CMP_CHROMA       256
  
      /**
       * ME diamond size & shape
       * - encoding: Set by user.
       * - decoding: unused
       */
      int dia_size;
  
      /**
       * amount of previous MV predictors (2a+1 x 2a+1 square)
       * - encoding: Set by user.
       * - decoding: unused
       */
      int last_predictor_count;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int pre_me;
  #endif
  
      /**
       * motion estimation prepass comparison function
       * - encoding: Set by user.
       * - decoding: unused
       */
      int me_pre_cmp;
  
      /**
       * ME prepass diamond size & shape
       * - encoding: Set by user.
       * - decoding: unused
       */
      int pre_dia_size;
  
      /**
       * subpel ME quality
       * - encoding: Set by user.
       * - decoding: unused
       */
      int me_subpel_quality;
  
      /**
       * maximum motion estimation search range in subpel units
       * If 0 then no limit.
       *
       * - encoding: Set by user.
       * - decoding: unused
       */
      int me_range;
  
      /**
       * slice flags
       * - encoding: unused
       * - decoding: Set by user.
       */
      int slice_flags;
  #define SLICE_FLAG_CODED_ORDER    0x0001 ///< draw_horiz_band() is called in coded order instead of display
  #define SLICE_FLAG_ALLOW_FIELD    0x0002 ///< allow draw_horiz_band() with field slices (MPEG-2 field pics)
  #define SLICE_FLAG_ALLOW_PLANE    0x0004 ///< allow draw_horiz_band() with 1 component at a time (SVQ1)
  
      /**
       * macroblock decision mode
       * - encoding: Set by user.
       * - decoding: unused
       */
      int mb_decision;
  #define FF_MB_DECISION_SIMPLE 0        ///< uses mb_cmp
  #define FF_MB_DECISION_BITS   1        ///< chooses the one which needs the fewest bits
  #define FF_MB_DECISION_RD     2        ///< rate distortion
  
      /**
       * custom intra quantization matrix
       * Must be allocated with the av_malloc() family of functions, and will be freed in
       * avcodec_free_context().
       * - encoding: Set/allocated by user, freed by include.libavcodec. Can be NULL.
       * - decoding: Set/allocated/freed by include.libavcodec.
       */
      uint16_t *intra_matrix;
  
      /**
       * custom inter quantization matrix
       * Must be allocated with the av_malloc() family of functions, and will be freed in
       * avcodec_free_context().
       * - encoding: Set/allocated by user, freed by include.libavcodec. Can be NULL.
       * - decoding: Set/allocated/freed by include.libavcodec.
       */
      uint16_t *inter_matrix;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int scenechange_threshold;
  
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int noise_reduction;
  #endif
  
      /**
       * precision of the intra DC coefficient - 8
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec
       */
      int intra_dc_precision;
  
      /**
       * Number of macroblock rows at the top which are skipped.
       * - encoding: unused
       * - decoding: Set by user.
       */
      int skip_top;
  
      /**
       * Number of macroblock rows at the bottom which are skipped.
       * - encoding: unused
       * - decoding: Set by user.
       */
      int skip_bottom;
  
      /**
       * minimum MB Lagrange multiplier
       * - encoding: Set by user.
       * - decoding: unused
       */
      int mb_lmin;
  
      /**
       * maximum MB Lagrange multiplier
       * - encoding: Set by user.
       * - decoding: unused
       */
      int mb_lmax;
  
  #if FF_API_PRIVATE_OPT
      /**
       * @deprecated use encoder private options instead
       */
      attribute_deprecated
      int me_penalty_compensation;
  #endif
  
      /**
       * - encoding: Set by user.
       * - decoding: unused
       */
      int bidir_refine;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int brd_scale;
  #endif
  
      /**
       * minimum GOP size
       * - encoding: Set by user.
       * - decoding: unused
       */
      int keyint_min;
  
      /**
       * number of reference frames
       * - encoding: Set by user.
       * - decoding: Set by lavc.
       */
      int refs;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int chromaoffset;
  #endif
  
      /**
       * Note: Value depends upon the compare function used for fullpel ME.
       * - encoding: Set by user.
       * - decoding: unused
       */
      int mv0_threshold;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int b_sensitivity;
  #endif
  
      /**
       * Chromaticity coordinates of the source primaries.
       * - encoding: Set by user
       * - decoding: Set by include.libavcodec
       */
      enum AVColorPrimaries color_primaries;
  
      /**
       * Color Transfer Characteristic.
       * - encoding: Set by user
       * - decoding: Set by include.libavcodec
       */
      enum AVColorTransferCharacteristic color_trc;
  
      /**
       * YUV colorspace type.
       * - encoding: Set by user
       * - decoding: Set by include.libavcodec
       */
      enum AVColorSpace colorspace;
  
      /**
       * MPEG vs JPEG YUV range.
       * - encoding: Set by user
       * - decoding: Set by include.libavcodec
       */
      enum AVColorRange color_range;
  
      /**
       * This defines the location of chroma samples.
       * - encoding: Set by user
       * - decoding: Set by include.libavcodec
       */
      enum AVChromaLocation chroma_sample_location;
  
      /**
       * Number of slices.
       * Indicates number of picture subdivisions. Used for parallelized
       * decoding.
       * - encoding: Set by user
       * - decoding: unused
       */
      int slices;
  
      /** Field order
       * - encoding: set by include.libavcodec
       * - decoding: Set by user.
       */
      enum AVFieldOrder field_order;
  
      /* audio only */
      int sample_rate; ///< samples per second
      int channels;    ///< number of audio channels
  
      /**
       * audio sample format
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
      enum AVSampleFormat sample_fmt;  ///< sample format
  
      /* The following data should not be initialized. */
      /**
       * Number of samples per channel in an audio frame.
       *
       * - encoding: set by include.libavcodec in avcodec_open2(). Each submitted frame
       *   except the last must contain exactly frame_size samples per channel.
       *   May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the
       *   frame size is not restricted.
       * - decoding: may be set by some decoders to indicate constant frame size
       */
      int frame_size;
  
      /**
       * Frame counter, set by include.libavcodec.
       *
       * - decoding: total number of frames returned from the decoder so far.
       * - encoding: total number of frames passed to the encoder so far.
       *
       *   @note the counter is not incremented if encoding/decoding resulted in
       *   an error.
       */
      int frame_number;
  
      /**
       * number of bytes per packet if constant and known or 0
       * Used by some WAV based audio codecs.
       */
      int block_align;
  
      /**
       * Audio cutoff bandwidth (0 means "automatic")
       * - encoding: Set by user.
       * - decoding: unused
       */
      int cutoff;
  
      /**
       * Audio channel layout.
       * - encoding: set by user.
       * - decoding: set by user, may be overwritten by include.libavcodec.
       */
      uint64_t channel_layout;
  
      /**
       * Request decoder to use this channel layout if it can (0 for default)
       * - encoding: unused
       * - decoding: Set by user.
       */
      uint64_t request_channel_layout;
  
      /**
       * Type of service that the audio stream conveys.
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
      enum AVAudioServiceType audio_service_type;
  
      /**
       * desired sample format
       * - encoding: Not used.
       * - decoding: Set by user.
       * Decoder will decode to this format if it can.
       */
      enum AVSampleFormat request_sample_fmt;
  
      /**
       * This callback is called at the beginning of each frame to get data
       * buffer(s) for it. There may be one contiguous buffer for all the data or
       * there may be a buffer per each data plane or anything in between. What
       * this means is, you may set however many entries in buf[] you feel necessary.
       * Each buffer must be reference-counted using the AVBuffer API (see description
       * of buf[] below).
       *
       * The following fields will be set in the frame before this callback is
       * called:
       * - format
       * - width, height (video only)
       * - sample_rate, channel_layout, nb_samples (audio only)
       * Their values may differ from the corresponding values in
       * AVCodecContext. This callback must use the frame values, not the codec
       * context values, to calculate the required buffer size.
       *
       * This callback must fill the following fields in the frame:
       * - data[]
       * - linesize[]
       * - extended_data:
       *   * if the data is planar audio with more than 8 channels, then this
       *     callback must allocate and fill extended_data to contain all pointers
       *     to all data planes. data[] must hold as many pointers as it can.
       *     extended_data must be allocated with av_malloc() and will be freed in
       *     av_frame_unref().
       *   * otherwise extended_data must point to data
       * - buf[] must contain one or more pointers to AVBufferRef structures. Each of
       *   the frame's data and extended_data pointers must be contained in these. That
       *   is, one AVBufferRef for each allocated chunk of memory, not necessarily one
       *   AVBufferRef per data[] entry. See: av_buffer_create(), av_buffer_alloc(),
       *   and av_buffer_ref().
       * - extended_buf and nb_extended_buf must be allocated with av_malloc() by
       *   this callback and filled with the extra buffers if there are more
       *   buffers than buf[] can hold. extended_buf will be freed in
       *   av_frame_unref().
       *
       * If AV_CODEC_CAP_DR1 is not set then get_buffer2() must call
       * avcodec_default_get_buffer2() instead of providing buffers allocated by
       * some other means.
       *
       * Each data plane must be aligned to the maximum required by the target
       * CPU.
       *
       * @see avcodec_default_get_buffer2()
       *
       * Video:
       *
       * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
       * (read and/or written to if it is writable) later by include.libavcodec.
       *
       * avcodec_align_dimensions2() should be used to find the required width and
       * height, as they normally need to be rounded up to the next multiple of 16.
       *
       * Some decoders do not support linesizes changing between frames.
       *
       * If frame multithreading is used, this callback may be called from a
       * different thread, but not from more than one at once. Does not need to be
       * reentrant.
       *
       * @see avcodec_align_dimensions2()
       *
       * Audio:
       *
       * Decoders request a buffer of a particular size by setting
       * AVFrame.nb_samples prior to calling get_buffer2(). The decoder may,
       * however, utilize only part of the buffer by setting AVFrame.nb_samples
       * to a smaller value in the output frame.
       *
       * As a convenience, av_samples_get_buffer_size() and
       * av_samples_fill_arrays() in include.libavutil may be used by custom get_buffer2()
       * functions to find the required data size and to fill data pointers and
       * linesize. In AVFrame.linesize, only linesize[0] may be set for audio
       * since all planes must be the same size.
       *
       * @see av_samples_get_buffer_size(), av_samples_fill_arrays()
       *
       * - encoding: unused
       * - decoding: Set by include.libavcodec, user can override.
       */
      int (*get_buffer2)(struct AVCodecContext *s, AVFrame *frame, int flags);
  
  #if FF_API_OLD_ENCDEC
      /**
       * If non-zero, the decoded audio and video frames returned from
       * avcodec_decode_video2() and avcodec_decode_audio4() are reference-counted
       * and are valid indefinitely. The caller must free them with
       * av_frame_unref() when they are not needed anymore.
       * Otherwise, the decoded frames must not be freed by the caller and are
       * only valid until the next decode call.
       *
       * This is always automatically enabled if avcodec_receive_frame() is used.
       *
       * - encoding: unused
       * - decoding: set by the caller before avcodec_open2().
       */
      attribute_deprecated
      int refcounted_frames;
  #endif
  
      /* - encoding parameters */
      float qcompress;  ///< amount of qscale change between easy & hard scenes (0.0-1.0)
      float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)
  
      /**
       * minimum quantizer
       * - encoding: Set by user.
       * - decoding: unused
       */
      int qmin;
  
      /**
       * maximum quantizer
       * - encoding: Set by user.
       * - decoding: unused
       */
      int qmax;
  
      /**
       * maximum quantizer difference between frames
       * - encoding: Set by user.
       * - decoding: unused
       */
      int max_qdiff;
  
      /**
       * decoder bitstream buffer size
       * - encoding: Set by user.
       * - decoding: unused
       */
      int rc_buffer_size;
  
      /**
       * ratecontrol override, see RcOverride
       * - encoding: Allocated/set/freed by user.
       * - decoding: unused
       */
      int rc_override_count;
      RcOverride *rc_override;
  
      /**
       * maximum bitrate
       * - encoding: Set by user.
       * - decoding: Set by user, may be overwritten by include.libavcodec.
       */
      int64_t rc_max_rate;
  
      /**
       * minimum bitrate
       * - encoding: Set by user.
       * - decoding: unused
       */
      int64_t rc_min_rate;
  
      /**
       * Ratecontrol attempt to use, at maximum, <value> of what can be used without an underflow.
       * - encoding: Set by user.
       * - decoding: unused.
       */
      float rc_max_available_vbv_use;
  
      /**
       * Ratecontrol attempt to use, at least, <value> times the amount needed to prevent a vbv overflow.
       * - encoding: Set by user.
       * - decoding: unused.
       */
      float rc_min_vbv_overflow_use;
  
      /**
       * Number of bits which should be loaded into the rc buffer before decoding starts.
       * - encoding: Set by user.
       * - decoding: unused
       */
      int rc_initial_buffer_occupancy;
  
  #if FF_API_CODER_TYPE
  #define FF_CODER_TYPE_VLC       0
  #define FF_CODER_TYPE_AC        1
  #define FF_CODER_TYPE_RAW       2
  #define FF_CODER_TYPE_RLE       3
      /**
       * @deprecated use encoder private options instead
       */
      attribute_deprecated
      int coder_type;
  #endif /* FF_API_CODER_TYPE */
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int context_model;
  #endif
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int frame_skip_threshold;
  
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int frame_skip_factor;
  
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int frame_skip_exp;
  
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int frame_skip_cmp;
  #endif /* FF_API_PRIVATE_OPT */
  
      /**
       * trellis RD quantization
       * - encoding: Set by user.
       * - decoding: unused
       */
      int trellis;
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int min_prediction_order;
  
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int max_prediction_order;
  
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int64_t timecode_frame_start;
  #endif
  
  #if FF_API_RTP_CALLBACK
      /**
       * @deprecated unused
       */
      /* The RTP callback: This function is called    */
      /* every time the encoder has a packet to send. */
      /* It depends on the encoder if the data starts */
      /* with a Start Code (it should). H.263 does.   */
      /* mb_nb contains the number of macroblocks     */
      /* encoded in the RTP payload.                  */
      attribute_deprecated
      void (*rtp_callback)(struct AVCodecContext *avctx, void *data, int size, int mb_nb);
  #endif
  
  #if FF_API_PRIVATE_OPT
      /** @deprecated use encoder private options instead */
      attribute_deprecated
      int rtp_payload_size;   /* The size of the RTP payload: the coder will  */
                              /* do its best to deliver a chunk with size     */
                              /* below rtp_payload_size, the chunk will start */
                              /* with a start code on some codecs like H.263. */
                              /* This doesn't take account of any particular  */
                              /* headers inside the transmitted RTP payload.  */
  #endif
  
  #if FF_API_STAT_BITS
      /* statistics, used for 2-pass encoding */
      attribute_deprecated
      int mv_bits;
      attribute_deprecated
      int header_bits;
      attribute_deprecated
      int i_tex_bits;
      attribute_deprecated
      int p_tex_bits;
      attribute_deprecated
      int i_count;
      attribute_deprecated
      int p_count;
      attribute_deprecated
      int skip_count;
      attribute_deprecated
      int misc_bits;
  
      /** @deprecated this field is unused */
      attribute_deprecated
      int frame_bits;
  #endif
  
      /**
       * pass1 encoding statistics output buffer
       * - encoding: Set by include.libavcodec.
       * - decoding: unused
       */
      char *stats_out;
  
      /**
       * pass2 encoding statistics input buffer
       * Concatenated stuff from stats_out of pass1 should be placed here.
       * - encoding: Allocated/set/freed by user.
       * - decoding: unused
       */
      char *stats_in;
  
      /**
       * Work around bugs in encoders which sometimes cannot be detected automatically.
       * - encoding: Set by user
       * - decoding: Set by user
       */
      int workaround_bugs;
  #define FF_BUG_AUTODETECT       1  ///< autodetection
  #define FF_BUG_XVID_ILACE       4
  #define FF_BUG_UMP4             8
  #define FF_BUG_NO_PADDING       16
  #define FF_BUG_AMV              32
  #define FF_BUG_QPEL_CHROMA      64
  #define FF_BUG_STD_QPEL         128
  #define FF_BUG_QPEL_CHROMA2     256
  #define FF_BUG_DIRECT_BLOCKSIZE 512
  #define FF_BUG_EDGE             1024
  #define FF_BUG_HPEL_CHROMA      2048
  #define FF_BUG_DC_CLIP          4096
  #define FF_BUG_MS               8192 ///< Work around various bugs in Microsoft's broken decoders.
  #define FF_BUG_TRUNCATED       16384
  #define FF_BUG_IEDGE           32768
  
      /**
       * strictly follow the standard (MPEG-4, ...).
       * - encoding: Set by user.
       * - decoding: Set by user.
       * Setting this to STRICT or higher means the encoder and decoder will
       * generally do stupid things, whereas setting it to unofficial or lower
       * will mean the encoder might produce output that is not supported by all
       * spec-compliant decoders. Decoders don't differentiate between normal,
       * unofficial and experimental (that is, they always try to decode things
       * when they can) unless they are explicitly asked to behave stupidly
       * (=strictly conform to the specs)
       */
      int strict_std_compliance;
  #define FF_COMPLIANCE_VERY_STRICT   2 ///< Strictly conform to an older more strict version of the spec or reference software.
  #define FF_COMPLIANCE_STRICT        1 ///< Strictly conform to all the things in the spec no matter what consequences.
  #define FF_COMPLIANCE_NORMAL        0
  #define FF_COMPLIANCE_UNOFFICIAL   -1 ///< Allow unofficial extensions
  #define FF_COMPLIANCE_EXPERIMENTAL -2 ///< Allow nonstandardized experimental things.
  
      /**
       * error concealment flags
       * - encoding: unused
       * - decoding: Set by user.
       */
      int error_concealment;
  #define FF_EC_GUESS_MVS   1
  #define FF_EC_DEBLOCK     2
  #define FF_EC_FAVOR_INTER 256
  
      /**
       * debug
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      int debug;
  #define FF_DEBUG_PICT_INFO   1
  #define FF_DEBUG_RC          2
  #define FF_DEBUG_BITSTREAM   4
  #define FF_DEBUG_MB_TYPE     8
  #define FF_DEBUG_QP          16
  #define FF_DEBUG_DCT_COEFF   0x00000040
  #define FF_DEBUG_SKIP        0x00000080
  #define FF_DEBUG_STARTCODE   0x00000100
  #define FF_DEBUG_ER          0x00000400
  #define FF_DEBUG_MMCO        0x00000800
  #define FF_DEBUG_BUGS        0x00001000
  #define FF_DEBUG_BUFFERS     0x00008000
  #define FF_DEBUG_THREADS     0x00010000
  #define FF_DEBUG_GREEN_MD    0x00800000
  #define FF_DEBUG_NOMC        0x01000000
  
      /**
       * Error recognition; may misdetect some more or less valid parts as errors.
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      int err_recognition;
  
  /**
   * Verify checksums embedded in the bitstream (could be of either encoded or
   * decoded data, depending on the codec) and print an error message on mismatch.
   * If AV_EF_EXPLODE is also set, a mismatching checksum will result in the
   * decoder returning an error.
   */
  #define AV_EF_CRCCHECK  (1<<0)
  #define AV_EF_BITSTREAM (1<<1)          ///< detect bitstream specification deviations
  #define AV_EF_BUFFER    (1<<2)          ///< detect improper bitstream length
  #define AV_EF_EXPLODE   (1<<3)          ///< abort decoding on minor error detection
  
  #define AV_EF_IGNORE_ERR (1<<15)        ///< ignore errors and continue
  #define AV_EF_CAREFUL    (1<<16)        ///< consider things that violate the spec, are fast to calculate and have not been seen in the wild as errors
  #define AV_EF_COMPLIANT  (1<<17)        ///< consider all spec non compliances as errors
  #define AV_EF_AGGRESSIVE (1<<18)        ///< consider things that a sane encoder should not do as an error
  
  
      /**
       * opaque 64-bit number (generally a PTS) that will be reordered and
       * output in AVFrame.reordered_opaque
       * - encoding: Set by include.libavcodec to the reordered_opaque of the input
       *             frame corresponding to the last returned packet. Only
       *             supported by encoders with the
       *             AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE capability.
       * - decoding: Set by user.
       */
      int64_t reordered_opaque;
  
      /**
       * Hardware accelerator in use
       * - encoding: unused.
       * - decoding: Set by include.libavcodec
       */
      const struct AVHWAccel *hwaccel;
  
      /**
       * Hardware accelerator context.
       * For some hardware accelerators, a global context needs to be
       * provided by the user. In that case, this holds display-dependent
       * data FFmpeg cannot instantiate itself. Please refer to the
       * FFmpeg HW accelerator documentation to know how to fill this
       * is. e.g. for VA API, this is a struct vaapi_context.
       * - encoding: unused
       * - decoding: Set by user
       */
      void *hwaccel_context;
  
      /**
       * error
       * - encoding: Set by include.libavcodec if flags & AV_CODEC_FLAG_PSNR.
       * - decoding: unused
       */
      uint64_t error[AV_NUM_DATA_POINTERS];
  
      /**
       * DCT algorithm, see FF_DCT_* below
       * - encoding: Set by user.
       * - decoding: unused
       */
      int dct_algo;
  #define FF_DCT_AUTO    0
  #define FF_DCT_FASTINT 1
  #define FF_DCT_INT     2
  #define FF_DCT_MMX     3
  #define FF_DCT_ALTIVEC 5
  #define FF_DCT_FAAN    6
  
      /**
       * IDCT algorithm, see FF_IDCT_* below.
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      int idct_algo;
  #define FF_IDCT_AUTO          0
  #define FF_IDCT_INT           1
  #define FF_IDCT_SIMPLE        2
  #define FF_IDCT_SIMPLEMMX     3
  #define FF_IDCT_ARM           7
  #define FF_IDCT_ALTIVEC       8
  #define FF_IDCT_SIMPLEARM     10
  #define FF_IDCT_XVID          14
  #define FF_IDCT_SIMPLEARMV5TE 16
  #define FF_IDCT_SIMPLEARMV6   17
  #define FF_IDCT_FAAN          20
  #define FF_IDCT_SIMPLENEON    22
  #define FF_IDCT_NONE          24 /* Used by XvMC to extract IDCT coefficients with FF_IDCT_PERM_NONE */
  #define FF_IDCT_SIMPLEAUTO    128
  
      /**
       * bits per sample/pixel from the demuxer (needed for huffyuv).
       * - encoding: Set by include.libavcodec.
       * - decoding: Set by user.
       */
       int bits_per_coded_sample;
  
      /**
       * Bits per sample/pixel of internal include.libavcodec pixel/sample format.
       * - encoding: set by user.
       * - decoding: set by include.libavcodec.
       */
      int bits_per_raw_sample;
  
      /**
       * low resolution decoding, 1-> 1/2 size, 2->1/4 size
       * - encoding: unused
       * - decoding: Set by user.
       */
       int lowres;
  
  #if FF_API_CODED_FRAME
      /**
       * the picture in the bitstream
       * - encoding: Set by include.libavcodec.
       * - decoding: unused
       *
       * @deprecated use the quality factor packet side data instead
       */
      attribute_deprecated AVFrame *coded_frame;
  #endif
  
      /**
       * thread count
       * is used to decide how many independent tasks should be passed to execute()
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      int thread_count;
  
      /**
       * Which multithreading methods to use.
       * Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread,
       * so clients which cannot provide future frames should not use it.
       *
       * - encoding: Set by user, otherwise the default is used.
       * - decoding: Set by user, otherwise the default is used.
       */
      int thread_type;
  #define FF_THREAD_FRAME   1 ///< Decode more than one frame at once
  #define FF_THREAD_SLICE   2 ///< Decode more than one part of a single frame at once
  
      /**
       * Which multithreading methods are in use by the codec.
       * - encoding: Set by include.libavcodec.
       * - decoding: Set by include.libavcodec.
       */
      int active_thread_type;
  
  #if FF_API_THREAD_SAFE_CALLBACKS
      /**
       * Set by the client if its custom get_buffer() callback can be called
       * synchronously from another thread, which allows faster multithreaded decoding.
       * draw_horiz_band() will be called from other threads regardless of this setting.
       * Ignored if the default get_buffer() is used.
       * - encoding: Set by user.
       * - decoding: Set by user.
       *
       * @deprecated the custom get_buffer2() callback should always be
       *   thread-safe. Thread-unsafe get_buffer2() implementations will be
       *   invalid starting with LIBAVCODEC_VERSION_MAJOR=60; in other words,
       *   include.libavcodec will behave as if this field was always set to 1.
       *   Callers that want to be forward compatible with future include.libavcodec
       *   versions should wrap access to this field in
       *     #if LIBAVCODEC_VERSION_MAJOR < 60
       */
      attribute_deprecated
      int thread_safe_callbacks;
  #endif
  
      /**
       * The codec may call this to execute several independent things.
       * It will return only after finishing all tasks.
       * The user may replace this with some multithreaded implementation,
       * the default implementation will execute the parts serially.
       * @param count the number of things to execute
       * - encoding: Set by include.libavcodec, user can override.
       * - decoding: Set by include.libavcodec, user can override.
       */
      int (*execute)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg), void *arg2, int *ret, int count, int size);
  
      /**
       * The codec may call this to execute several independent things.
       * It will return only after finishing all tasks.
       * The user may replace this with some multithreaded implementation,
       * the default implementation will execute the parts serially.
       * Also see avcodec_thread_init and e.g. the --enable-pthread configure option.
       * @param c context passed also to func
       * @param count the number of things to execute
       * @param arg2 argument passed unchanged to func
       * @param ret return values of executed functions, must have space for "count" values. May be NULL.
       * @param func function that will be called count times, with jobnr from 0 to count-1.
       *             threadnr will be in the range 0 to c->thread_count-1 < MAX_THREADS and so that no
       *             two instances of func executing at the same time will have the same threadnr.
       * @return always 0 currently, but code should handle a future improvement where when any call to func
       *         returns < 0 no further calls to func may be done and < 0 is returned.
       * - encoding: Set by include.libavcodec, user can override.
       * - decoding: Set by include.libavcodec, user can override.
       */
      int (*execute2)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg, int jobnr, int threadnr), void *arg2, int *ret, int count);
  
      /**
       * noise vs. sse weight for the nsse comparison function
       * - encoding: Set by user.
       * - decoding: unused
       */
       int nsse_weight;
  
      /**
       * profile
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
       int profile;
  #define FF_PROFILE_UNKNOWN -99
  #define FF_PROFILE_RESERVED -100
  
  #define FF_PROFILE_AAC_MAIN 0
  #define FF_PROFILE_AAC_LOW  1
  #define FF_PROFILE_AAC_SSR  2
  #define FF_PROFILE_AAC_LTP  3
  #define FF_PROFILE_AAC_HE   4
  #define FF_PROFILE_AAC_HE_V2 28
  #define FF_PROFILE_AAC_LD   22
  #define FF_PROFILE_AAC_ELD  38
  #define FF_PROFILE_MPEG2_AAC_LOW 128
  #define FF_PROFILE_MPEG2_AAC_HE  131
  
  #define FF_PROFILE_DNXHD         0
  #define FF_PROFILE_DNXHR_LB      1
  #define FF_PROFILE_DNXHR_SQ      2
  #define FF_PROFILE_DNXHR_HQ      3
  #define FF_PROFILE_DNXHR_HQX     4
  #define FF_PROFILE_DNXHR_444     5
  
  #define FF_PROFILE_DTS         20
  #define FF_PROFILE_DTS_ES      30
  #define FF_PROFILE_DTS_96_24   40
  #define FF_PROFILE_DTS_HD_HRA  50
  #define FF_PROFILE_DTS_HD_MA   60
  #define FF_PROFILE_DTS_EXPRESS 70
  
  #define FF_PROFILE_MPEG2_422    0
  #define FF_PROFILE_MPEG2_HIGH   1
  #define FF_PROFILE_MPEG2_SS     2
  #define FF_PROFILE_MPEG2_SNR_SCALABLE  3
  #define FF_PROFILE_MPEG2_MAIN   4
  #define FF_PROFILE_MPEG2_SIMPLE 5
  
  #define FF_PROFILE_H264_CONSTRAINED  (1<<9)  // 8+1; constraint_set1_flag
  #define FF_PROFILE_H264_INTRA        (1<<11) // 8+3; constraint_set3_flag
  
  #define FF_PROFILE_H264_BASELINE             66
  #define FF_PROFILE_H264_CONSTRAINED_BASELINE (66|FF_PROFILE_H264_CONSTRAINED)
  #define FF_PROFILE_H264_MAIN                 77
  #define FF_PROFILE_H264_EXTENDED             88
  #define FF_PROFILE_H264_HIGH                 100
  #define FF_PROFILE_H264_HIGH_10              110
  #define FF_PROFILE_H264_HIGH_10_INTRA        (110|FF_PROFILE_H264_INTRA)
  #define FF_PROFILE_H264_MULTIVIEW_HIGH       118
  #define FF_PROFILE_H264_HIGH_422             122
  #define FF_PROFILE_H264_HIGH_422_INTRA       (122|FF_PROFILE_H264_INTRA)
  #define FF_PROFILE_H264_STEREO_HIGH          128
  #define FF_PROFILE_H264_HIGH_444             144
  #define FF_PROFILE_H264_HIGH_444_PREDICTIVE  244
  #define FF_PROFILE_H264_HIGH_444_INTRA       (244|FF_PROFILE_H264_INTRA)
  #define FF_PROFILE_H264_CAVLC_444            44
  
  #define FF_PROFILE_VC1_SIMPLE   0
  #define FF_PROFILE_VC1_MAIN     1
  #define FF_PROFILE_VC1_COMPLEX  2
  #define FF_PROFILE_VC1_ADVANCED 3
  
  #define FF_PROFILE_MPEG4_SIMPLE                     0
  #define FF_PROFILE_MPEG4_SIMPLE_SCALABLE            1
  #define FF_PROFILE_MPEG4_CORE                       2
  #define FF_PROFILE_MPEG4_MAIN                       3
  #define FF_PROFILE_MPEG4_N_BIT                      4
  #define FF_PROFILE_MPEG4_SCALABLE_TEXTURE           5
  #define FF_PROFILE_MPEG4_SIMPLE_FACE_ANIMATION      6
  #define FF_PROFILE_MPEG4_BASIC_ANIMATED_TEXTURE     7
  #define FF_PROFILE_MPEG4_HYBRID                     8
  #define FF_PROFILE_MPEG4_ADVANCED_REAL_TIME         9
  #define FF_PROFILE_MPEG4_CORE_SCALABLE             10
  #define FF_PROFILE_MPEG4_ADVANCED_CODING           11
  #define FF_PROFILE_MPEG4_ADVANCED_CORE             12
  #define FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE 13
  #define FF_PROFILE_MPEG4_SIMPLE_STUDIO             14
  #define FF_PROFILE_MPEG4_ADVANCED_SIMPLE           15
  
  #define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_0   1
  #define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_1   2
  #define FF_PROFILE_JPEG2000_CSTREAM_NO_RESTRICTION  32768
  #define FF_PROFILE_JPEG2000_DCINEMA_2K              3
  #define FF_PROFILE_JPEG2000_DCINEMA_4K              4
  
  #define FF_PROFILE_VP9_0                            0
  #define FF_PROFILE_VP9_1                            1
  #define FF_PROFILE_VP9_2                            2
  #define FF_PROFILE_VP9_3                            3
  
  #define FF_PROFILE_HEVC_MAIN                        1
  #define FF_PROFILE_HEVC_MAIN_10                     2
  #define FF_PROFILE_HEVC_MAIN_STILL_PICTURE          3
  #define FF_PROFILE_HEVC_REXT                        4
  
  #define FF_PROFILE_VVC_MAIN_10                      1
  #define FF_PROFILE_VVC_MAIN_10_444                 33
  
  #define FF_PROFILE_AV1_MAIN                         0
  #define FF_PROFILE_AV1_HIGH                         1
  #define FF_PROFILE_AV1_PROFESSIONAL                 2
  
  #define FF_PROFILE_MJPEG_HUFFMAN_BASELINE_DCT            0xc0
  #define FF_PROFILE_MJPEG_HUFFMAN_EXTENDED_SEQUENTIAL_DCT 0xc1
  #define FF_PROFILE_MJPEG_HUFFMAN_PROGRESSIVE_DCT         0xc2
  #define FF_PROFILE_MJPEG_HUFFMAN_LOSSLESS                0xc3
  #define FF_PROFILE_MJPEG_JPEG_LS                         0xf7
  
  #define FF_PROFILE_SBC_MSBC                         1
  
  #define FF_PROFILE_PRORES_PROXY     0
  #define FF_PROFILE_PRORES_LT        1
  #define FF_PROFILE_PRORES_STANDARD  2
  #define FF_PROFILE_PRORES_HQ        3
  #define FF_PROFILE_PRORES_4444      4
  #define FF_PROFILE_PRORES_XQ        5
  
  #define FF_PROFILE_ARIB_PROFILE_A 0
  #define FF_PROFILE_ARIB_PROFILE_C 1
  
  #define FF_PROFILE_KLVA_SYNC 0
  #define FF_PROFILE_KLVA_ASYNC 1
  
      /**
       * level
       * - encoding: Set by user.
       * - decoding: Set by include.libavcodec.
       */
       int level;
  #define FF_LEVEL_UNKNOWN -99
  
      /**
       * Skip loop filtering for selected frames.
       * - encoding: unused
       * - decoding: Set by user.
       */
      enum AVDiscard skip_loop_filter;
  
      /**
       * Skip IDCT/dequantization for selected frames.
       * - encoding: unused
       * - decoding: Set by user.
       */
      enum AVDiscard skip_idct;
  
      /**
       * Skip decoding for selected frames.
       * - encoding: unused
       * - decoding: Set by user.
       */
      enum AVDiscard skip_frame;
  
      /**
       * Header containing style information for text subtitles.
       * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
       * [Script Info] and [V4+ Styles] section, plus the [Events] line and
       * the Format line following. It shouldn't include any Dialogue line.
       * - encoding: Set/allocated/freed by user (before avcodec_open2())
       * - decoding: Set/allocated/freed by include.libavcodec (by avcodec_open2())
       */
      uint8_t *subtitle_header;
      int subtitle_header_size;
  
  #if FF_API_VBV_DELAY
      /**
       * VBV delay coded in the last frame (in periods of a 27 MHz clock).
       * Used for compliant TS muxing.
       * - encoding: Set by include.libavcodec.
       * - decoding: unused.
       * @deprecated this value is now exported as a part of
       * AV_PKT_DATA_CPB_PROPERTIES packet side data
       */
      attribute_deprecated
      uint64_t vbv_delay;
  #endif
  
  #if FF_API_SIDEDATA_ONLY_PKT
      /**
       * Encoding only and set by default. Allow encoders to output packets
       * that do not contain any encoded data, only side data.
       *
       * Some encoders need to output such packets, e.g. to update some stream
       * parameters at the end of encoding.
       *
       * @deprecated this field disables the default behaviour and
       *             it is kept only for compatibility.
       */
      attribute_deprecated
      int side_data_only_packets;
  #endif
  
      /**
       * Audio only. The number of "priming" samples (padding) inserted by the
       * encoder at the beginning of the audio. I.e. this number of leading
       * decoded samples must be discarded by the caller to get the original audio
       * without leading padding.
       *
       * - decoding: unused
       * - encoding: Set by include.libavcodec. The timestamps on the output packets are
       *             adjusted by the encoder so that they always refer to the
       *             first sample of the data actually contained in the packet,
       *             including any added padding.  E.g. if the timebase is
       *             1/samplerate and the timestamp of the first input sample is
       *             0, the timestamp of the first output packet will be
       *             -initial_padding.
       */
      int initial_padding;
  
      /**
       * - decoding: For codecs that store a framerate value in the compressed
       *             bitstream, the decoder may export it here. { 0, 1} when
       *             unknown.
       * - encoding: May be used to signal the framerate of CFR content to an
       *             encoder.
       */
      AVRational framerate;
  
      /**
       * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
       * - encoding: unused.
       * - decoding: Set by include.libavcodec before calling get_format()
       */
      enum AVPixelFormat sw_pix_fmt;
  
      /**
       * Timebase in which pkt_dts/pts and AVPacket.dts/pts are.
       * - encoding unused.
       * - decoding set by user.
       */
      AVRational pkt_timebase;
  
      /**
       * AVCodecDescriptor
       * - encoding: unused.
       * - decoding: set by include.libavcodec.
       */
      const AVCodecDescriptor *codec_descriptor;
  
      /**
       * Current statistics for PTS correction.
       * - decoding: maintained and used by include.libavcodec, not intended to be used by user apps
       * - encoding: unused
       */
      int64_t pts_correction_num_faulty_pts; /// Number of incorrect PTS values so far
      int64_t pts_correction_num_faulty_dts; /// Number of incorrect DTS values so far
      int64_t pts_correction_last_pts;       /// PTS of the last frame
      int64_t pts_correction_last_dts;       /// DTS of the last frame
  
      /**
       * Character encoding of the input subtitles file.
       * - decoding: set by user
       * - encoding: unused
       */
      char *sub_charenc;
  
      /**
       * Subtitles character encoding mode. Formats or codecs might be adjusting
       * this setting (if they are doing the conversion themselves for instance).
       * - decoding: set by include.libavcodec
       * - encoding: unused
       */
      int sub_charenc_mode;
  #define FF_SUB_CHARENC_MODE_DO_NOTHING  -1  ///< do nothing (demuxer outputs a stream supposed to be already in UTF-8, or the codec is bitmap for instance)
  #define FF_SUB_CHARENC_MODE_AUTOMATIC    0  ///< include.libavcodec will select the mode itself
  #define FF_SUB_CHARENC_MODE_PRE_DECODER  1  ///< the AVPacket data needs to be recoded to UTF-8 before being fed to the decoder, requires iconv
  #define FF_SUB_CHARENC_MODE_IGNORE       2  ///< neither convert the subtitles, nor check them for valid UTF-8
  
      /**
       * Skip processing alpha if supported by codec.
       * Note that if the format uses pre-multiplied alpha (common with VP6,
       * and recommended due to better video quality/compression)
       * the image will look as if alpha-blended onto a black background.
       * However for formats that do not use pre-multiplied alpha
       * there might be serious artefacts (though e.g. include.libswscale currently
       * assumes pre-multiplied alpha anyway).
       *
       * - decoding: set by user
       * - encoding: unused
       */
      int skip_alpha;
  
      /**
       * Number of samples to skip after a discontinuity
       * - decoding: unused
       * - encoding: set by include.libavcodec
       */
      int seek_preroll;
  
  #if FF_API_DEBUG_MV
      /**
       * @deprecated unused
       */
      attribute_deprecated
      int debug_mv;
  #define FF_DEBUG_VIS_MV_P_FOR  0x00000001 //visualize forward predicted MVs of P frames
  #define FF_DEBUG_VIS_MV_B_FOR  0x00000002 //visualize forward predicted MVs of B frames
  #define FF_DEBUG_VIS_MV_B_BACK 0x00000004 //visualize backward predicted MVs of B frames
  #endif
  
      /**
       * custom intra quantization matrix
       * - encoding: Set by user, can be NULL.
       * - decoding: unused.
       */
      uint16_t *chroma_intra_matrix;
  
      /**
       * dump format separator.
       * can be ", " or "\n      " or anything else
       * - encoding: Set by user.
       * - decoding: Set by user.
       */
      uint8_t *dump_separator;
  
      /**
       * ',' separated list of allowed decoders.
       * If NULL then all are allowed
       * - encoding: unused
       * - decoding: set by user
       */
      char *codec_whitelist;
  
      /**
       * Properties of the stream that gets decoded
       * - encoding: unused
       * - decoding: set by include.libavcodec
       */
      unsigned properties;
  #define FF_CODEC_PROPERTY_LOSSLESS        0x00000001
  #define FF_CODEC_PROPERTY_CLOSED_CAPTIONS 0x00000002
  
      /**
       * Additional data associated with the entire coded stream.
       *
       * - decoding: unused
       * - encoding: may be set by include.libavcodec after avcodec_open2().
       */
      AVPacketSideData *coded_side_data;
      int            nb_coded_side_data;
  
      /**
       * A reference to the AVHWFramesContext describing the input (for encoding)
       * or output (decoding) frames. The reference is set by the caller and
       * afterwards owned (and freed) by include.libavcodec - it should never be read by
       * the caller after being set.
       *
       * - decoding: This field should be set by the caller from the get_format()
       *             callback. The previous reference (if any) will always be
       *             unreffed by include.libavcodec before the get_format() call.
       *
       *             If the default get_buffer2() is used with a hwaccel pixel
       *             format, then this AVHWFramesContext will be used for
       *             allocating the frame buffers.
       *
       * - encoding: For hardware encoders configured to use a hwaccel pixel
       *             format, this field should be set by the caller to a reference
       *             to the AVHWFramesContext describing input frames.
       *             AVHWFramesContext.format must be equal to
       *             AVCodecContext.pix_fmt.
       *
       *             This field should be set before avcodec_open2() is called.
       */
      AVBufferRef *hw_frames_ctx;
  
      /**
       * Control the form of AVSubtitle.rects[N]->ass
       * - decoding: set by user
       * - encoding: unused
       */
      int sub_text_format;
  #define FF_SUB_TEXT_FMT_ASS              0
  #if FF_API_ASS_TIMING
  #define FF_SUB_TEXT_FMT_ASS_WITH_TIMINGS 1
  #endif
  
      /**
       * Audio only. The amount of padding (in samples) appended by the encoder to
       * the end of the audio. I.e. this number of decoded samples must be
       * discarded by the caller from the end of the stream to get the original
       * audio without any trailing padding.
       *
       * - decoding: unused
       * - encoding: unused
       */
      int trailing_padding;
  
      /**
       * The number of pixels per image to maximally accept.
       *
       * - decoding: set by user
       * - encoding: set by user
       */
      int64_t max_pixels;
  
      /**
       * A reference to the AVHWDeviceContext describing the device which will
       * be used by a hardware encoder/decoder.  The reference is set by the
       * caller and afterwards owned (and freed) by include.libavcodec.
       *
       * This should be used if either the codec device does not require
       * hardware frames or any that are used are to be allocated internally by
       * include.libavcodec.  If the user wishes to supply any of the frames used as
       * encoder input or decoder output then hw_frames_ctx should be used
       * instead.  When hw_frames_ctx is set in get_format() for a decoder, this
       * field will be ignored while decoding the associated stream segment, but
       * may again be used on a following one after another get_format() call.
       *
       * For both encoders and decoders this field should be set before
       * avcodec_open2() is called and must not be written to thereafter.
       *
       * Note that some decoders may require this field to be set initially in
       * order to support hw_frames_ctx at all - in that case, all frames
       * contexts used must be created on the same device.
       */
      AVBufferRef *hw_device_ctx;
  
      /**
       * Bit set of AV_HWACCEL_FLAG_* flags, which affect hardware accelerated
       * decoding (if active).
       * - encoding: unused
       * - decoding: Set by user (either before avcodec_open2(), or in the
       *             AVCodecContext.get_format callback)
       */
      int hwaccel_flags;
  
      /**
       * Video decoding only. Certain video codecs support cropping, meaning that
       * only a sub-rectangle of the decoded frame is intended for display.  This
       * option controls how cropping is handled by include.libavcodec.
       *
       * When set to 1 (the default), include.libavcodec will apply cropping internally.
       * I.e. it will modify the output frame width/height fields and offset the
       * data pointers (only by as much as possible while preserving alignment, or
       * by the full amount if the AV_CODEC_FLAG_UNALIGNED flag is set) so that
       * the frames output by the decoder refer only to the cropped area. The
       * crop_* fields of the output frames will be zero.
       *
       * When set to 0, the width/height fields of the output frames will be set
       * to the coded dimensions and the crop_* fields will describe the cropping
       * rectangle. Applying the cropping is left to the caller.
       *
       * @warning When hardware acceleration with opaque output frames is used,
       * include.libavcodec is unable to apply cropping from the top/left border.
       *
       * @note when this option is set to zero, the width/height fields of the
       * AVCodecContext and output AVFrames have different meanings. The codec
       * context fields store display dimensions (with the coded dimensions in
       * coded_width/height), while the frame fields store the coded dimensions
       * (with the display dimensions being determined by the crop_* fields).
       */
      int apply_cropping;
  
      /*
       * Video decoding only.  Sets the number of extra hardware frames which
       * the decoder will allocate for use by the caller.  This must be set
       * before avcodec_open2() is called.
       *
       * Some hardware decoders require all frames that they will use for
       * output to be defined in advance before decoding starts.  For such
       * decoders, the hardware frame pool must therefore be of a fixed size.
       * The extra frames set here are on top of any number that the decoder
       * needs internally in order to operate normally (for example, frames
       * used as reference pictures).
       */
      int extra_hw_frames;
  
      /**
       * The percentage of damaged samples to discard a frame.
       *
       * - decoding: set by user
       * - encoding: unused
       */
      int discard_damaged_percentage;
  
      /**
       * The number of samples per frame to maximally accept.
       *
       * - decoding: set by user
       * - encoding: set by user
       */
      int64_t max_samples;
  
      /**
       * Bit set of AV_CODEC_EXPORT_DATA_* flags, which affects the kind of
       * metadata exported in frame, packet, or coded stream side data by
       * decoders and encoders.
       *
       * - decoding: set by user
       * - encoding: set by user
       */
      int export_side_data;
  
      /**
       * This callback is called at the beginning of each packet to get a data
       * buffer for it.
       *
       * The following field will be set in the packet before this callback is
       * called:
       * - size
       * This callback must use the above value to calculate the required buffer size,
       * which must padded by at least AV_INPUT_BUFFER_PADDING_SIZE bytes.
       *
       * This callback must fill the following fields in the packet:
       * - data: alignment requirements for AVPacket apply, if any. Some architectures and
       *   encoders may benefit from having aligned data.
       * - buf: must contain a pointer to an AVBufferRef structure. The packet's
       *   data pointer must be contained in it. See: av_buffer_create(), av_buffer_alloc(),
       *   and av_buffer_ref().
       *
       * If AV_CODEC_CAP_DR1 is not set then get_encode_buffer() must call
       * avcodec_default_get_encode_buffer() instead of providing a buffer allocated by
       * some other means.
       *
       * The flags field may contain a combination of AV_GET_ENCODE_BUFFER_FLAG_ flags.
       * They may be used for example to hint what use the buffer may get after being
       * created.
       * Implementations of this callback may ignore flags they don't understand.
       * If AV_GET_ENCODE_BUFFER_FLAG_REF is set in flags then the packet may be reused
       * (read and/or written to if it is writable) later by include.libavcodec.
       *
       * This callback must be thread-safe, as when frame threading is used, it may
       * be called from multiple threads simultaneously.
       *
       * @see avcodec_default_get_encode_buffer()
       *
       * - encoding: Set by include.libavcodec, user can override.
       * - decoding: unused
       */
      int (*get_encode_buffer)(struct AVCodecContext *s, AVPacket *pkt, int flags);
  } AVCodecContext;
  
  #if FF_API_CODEC_GET_SET
  /**
   * Accessors for some AVCodecContext fields. These used to be provided for ABI
   * compatibility, and do not need to be used anymore.
   */
  attribute_deprecated
  AVRational av_codec_get_pkt_timebase         (const AVCodecContext *avctx);
  attribute_deprecated
  void       av_codec_set_pkt_timebase         (AVCodecContext *avctx, AVRational val);
  
  attribute_deprecated
  const AVCodecDescriptor *av_codec_get_codec_descriptor(const AVCodecContext *avctx);
  attribute_deprecated
  void                     av_codec_set_codec_descriptor(AVCodecContext *avctx, const AVCodecDescriptor *desc);
  
  attribute_deprecated
  unsigned av_codec_get_codec_properties(const AVCodecContext *avctx);
  
  attribute_deprecated
  int  av_codec_get_lowres(const AVCodecContext *avctx);
  attribute_deprecated
  void av_codec_set_lowres(AVCodecContext *avctx, int val);
  
  attribute_deprecated
  int  av_codec_get_seek_preroll(const AVCodecContext *avctx);
  attribute_deprecated
  void av_codec_set_seek_preroll(AVCodecContext *avctx, int val);
  
  attribute_deprecated
  uint16_t *av_codec_get_chroma_intra_matrix(const AVCodecContext *avctx);
  attribute_deprecated
  void av_codec_set_chroma_intra_matrix(AVCodecContext *avctx, uint16_t *val);
  #endif
  
  struct AVSubtitle;
  
  #if FF_API_CODEC_GET_SET
  attribute_deprecated
  int av_codec_get_max_lowres(const AVCodec *codec);
  #endif
  
  struct MpegEncContext;
  
  /**
   * @defgroup lavc_hwaccel AVHWAccel
   *
   * @note  Nothing in this structure should be accessed by the user.  At some
   *        point in future it will not be externally visible at all.
   *
   * @{
   */
  typedef struct AVHWAccel {
      /**
       * Name of the hardware accelerated codec.
       * The name is globally unique among encoders and among decoders (but an
       * encoder and a decoder can share the same name).
       */
      const char *name;
  
      /**
       * Type of codec implemented by the hardware accelerator.
       *
       * See AVMEDIA_TYPE_xxx
       */
      enum AVMediaType type;
  
      /**
       * Codec implemented by the hardware accelerator.
       *
       * See AV_CODEC_ID_xxx
       */
      enum AVCodecID id;
  
      /**
       * Supported pixel format.
       *
       * Only hardware accelerated formats are supported here.
       */
      enum AVPixelFormat pix_fmt;
  
      /**
       * Hardware accelerated codec capabilities.
       * see AV_HWACCEL_CODEC_CAP_*
       */
      int capabilities;
  
      /*****************************************************************
       * No fields below this line are part of the public API. They
       * may not be used outside of include.libavcodec and can be changed and
       * removed at will.
       * New public fields should be added right above.
       *****************************************************************
       */
  
      /**
       * Allocate a custom buffer
       */
      int (*alloc_frame)(AVCodecContext *avctx, AVFrame *frame);
  
      /**
       * Called at the beginning of each frame or field picture.
       *
       * Meaningful frame information (codec specific) is guaranteed to
       * be parsed at this point. This function is mandatory.
       *
       * Note that buf can be NULL along with buf_size set to 0.
       * Otherwise, this means the whole frame is available at this point.
       *
       * @param avctx the codec context
       * @param buf the frame data buffer base
       * @param buf_size the size of the frame in bytes
       * @return zero if successful, a negative value otherwise
       */
      int (*start_frame)(AVCodecContext *avctx, const uint8_t *buf, uint32_t buf_size);
  
      /**
       * Callback for parameter data (SPS/PPS/VPS etc).
       *
       * Useful for hardware decoders which keep persistent state about the
       * video parameters, and need to receive any changes to update that state.
       *
       * @param avctx the codec context
       * @param type the nal unit type
       * @param buf the nal unit data buffer
       * @param buf_size the size of the nal unit in bytes
       * @return zero if successful, a negative value otherwise
       */
      int (*decode_params)(AVCodecContext *avctx, int type, const uint8_t *buf, uint32_t buf_size);
  
      /**
       * Callback for each slice.
       *
       * Meaningful slice information (codec specific) is guaranteed to
       * be parsed at this point. This function is mandatory.
       * The only exception is XvMC, that works on MB level.
       *
       * @param avctx the codec context
       * @param buf the slice data buffer base
       * @param buf_size the size of the slice in bytes
       * @return zero if successful, a negative value otherwise
       */
      int (*decode_slice)(AVCodecContext *avctx, const uint8_t *buf, uint32_t buf_size);
  
      /**
       * Called at the end of each frame or field picture.
       *
       * The whole picture is parsed at this point and can now be sent
       * to the hardware accelerator. This function is mandatory.
       *
       * @param avctx the codec context
       * @return zero if successful, a negative value otherwise
       */
      int (*end_frame)(AVCodecContext *avctx);
  
      /**
       * Size of per-frame hardware accelerator private data.
       *
       * Private data is allocated with av_mallocz() before
       * AVCodecContext.get_buffer() and deallocated after
       * AVCodecContext.release_buffer().
       */
      int frame_priv_data_size;
  
      /**
       * Called for every Macroblock in a slice.
       *
       * XvMC uses it to replace the ff_mpv_reconstruct_mb().
       * Instead of decoding to raw picture, MB parameters are
       * stored in an array provided by the video driver.
       *
       * @param s the mpeg context
       */
      void (*decode_mb)(struct MpegEncContext *s);
  
      /**
       * Initialize the hwaccel private data.
       *
       * This will be called from ff_get_format(), after hwaccel and
       * hwaccel_context are set and the hwaccel private data in AVCodecInternal
       * is allocated.
       */
      int (*init)(AVCodecContext *avctx);
  
      /**
       * Uninitialize the hwaccel private data.
       *
       * This will be called from get_format() or avcodec_close(), after hwaccel
       * and hwaccel_context are already uninitialized.
       */
      int (*uninit)(AVCodecContext *avctx);
  
      /**
       * Size of the private data to allocate in
       * AVCodecInternal.hwaccel_priv_data.
       */
      int priv_data_size;
  
      /**
       * Internal hwaccel capabilities.
       */
      int caps_internal;
  
      /**
       * Fill the given hw_frames context with current codec parameters. Called
       * from get_format. Refer to avcodec_get_hw_frames_parameters() for
       * details.
       *
       * This CAN be called before AVHWAccel.init is called, and you must assume
       * that avctx->hwaccel_priv_data is invalid.
       */
      int (*frame_params)(AVCodecContext *avctx, AVBufferRef *hw_frames_ctx);
  } AVHWAccel;
  
  /**
   * HWAccel is experimental and is thus avoided in favor of non experimental
   * codecs
   */
  #define AV_HWACCEL_CODEC_CAP_EXPERIMENTAL 0x0200
  
  /**
   * Hardware acceleration should be used for decoding even if the codec level
   * used is unknown or higher than the maximum supported level reported by the
   * hardware driver.
   *
   * It's generally a good idea to pass this flag unless you have a specific
   * reason not to, as hardware tends to under-report supported levels.
   */
  #define AV_HWACCEL_FLAG_IGNORE_LEVEL (1 << 0)
  
  /**
   * Hardware acceleration can output YUV pixel formats with a different chroma
   * sampling than 4:2:0 and/or other than 8 bits per component.
   */
  #define AV_HWACCEL_FLAG_ALLOW_HIGH_DEPTH (1 << 1)
  
  /**
   * Hardware acceleration should still be attempted for decoding when the
   * codec profile does not match the reported capabilities of the hardware.
   *
   * For example, this can be used to try to decode baseline profile H.264
   * streams in hardware - it will often succeed, because many streams marked
   * as baseline profile actually conform to constrained baseline profile.
   *
   * @warning If the stream is actually not supported then the behaviour is
   *          undefined, and may include returning entirely incorrect output
   *          while indicating success.
   */
  #define AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH (1 << 2)
  
  /**
   * @}
   */
  
  #if FF_API_AVPICTURE
  /**
   * @defgroup lavc_picture AVPicture
   *
   * Functions for working with AVPicture
   * @{
   */
  
  /**
   * Picture data structure.
   *
   * Up to four components can be stored into it, the last component is
   * alpha.
   * @deprecated use AVFrame or imgutils functions instead
   */
  typedef struct AVPicture {
      attribute_deprecated
      uint8_t *data[AV_NUM_DATA_POINTERS];    ///< pointers to the image data planes
      attribute_deprecated
      int linesize[AV_NUM_DATA_POINTERS];     ///< number of bytes per line
  } AVPicture;
  
  /**
   * @}
   */
  #endif
  
  enum AVSubtitleType {
      SUBTITLE_NONE,
  
      SUBTITLE_BITMAP,                ///< A bitmap, pict will be set
  
      /**
       * Plain text, the text field must be set by the decoder and is
       * authoritative. ass and pict fields may contain approximations.
       */
      SUBTITLE_TEXT,
  
      /**
       * Formatted text, the ass field must be set by the decoder and is
       * authoritative. pict and text fields may contain approximations.
       */
      SUBTITLE_ASS,
  };
  
  #define AV_SUBTITLE_FLAG_FORCED 0x00000001
  
  typedef struct AVSubtitleRect {
      int x;         ///< top left corner  of pict, undefined when pict is not set
      int y;         ///< top left corner  of pict, undefined when pict is not set
      int w;         ///< width            of pict, undefined when pict is not set
      int h;         ///< height           of pict, undefined when pict is not set
      int nb_colors; ///< number of colors in pict, undefined when pict is not set
  
  #if FF_API_AVPICTURE
      /**
       * @deprecated unused
       */
      attribute_deprecated
      AVPicture pict;
  #endif
      /**
       * data+linesize for the bitmap of this subtitle.
       * Can be set for text/ass as well once they are rendered.
       */
      uint8_t *data[4];
      int linesize[4];
  
      enum AVSubtitleType type;
  
      char *text;                     ///< 0 terminated plain UTF-8 text
  
      /**
       * 0 terminated ASS/SSA compatible event line.
       * The presentation of this is unaffected by the other values in this
       * struct.
       */
      char *ass;
  
      int flags;
  } AVSubtitleRect;
  
  typedef struct AVSubtitle {
      uint16_t format; /* 0 = graphics */
      uint32_t start_display_time; /* relative to packet pts, in ms */
      uint32_t end_display_time; /* relative to packet pts, in ms */
      unsigned num_rects;
      AVSubtitleRect **rects;
      int64_t pts;    ///< Same as packet pts, in AV_TIME_BASE
  } AVSubtitle;
  
  #if FF_API_NEXT
  /**
   * If c is NULL, returns the first registered codec,
   * if c is non-NULL, returns the next registered codec after c,
   * or NULL if c is the last one.
   */
  attribute_deprecated
  AVCodec *av_codec_next(const AVCodec *c);
  #endif
  
  /**
   * Return the LIBAVCODEC_VERSION_INT constant.
   */
  unsigned avcodec_version(void);
  
  /**
   * Return the include.libavcodec build-time configuration.
   */
  const char *avcodec_configuration(void);
  
  /**
   * Return the include.libavcodec license.
   */
  const char *avcodec_license(void);
  
  #if FF_API_NEXT
  /**
   * @deprecated Calling this function is unnecessary.
   */
  attribute_deprecated
  void avcodec_register(AVCodec *codec);
  
  /**
   * @deprecated Calling this function is unnecessary.
   */
  attribute_deprecated
  void avcodec_register_all(void);
  #endif
  
  /**
   * Allocate an AVCodecContext and set its fields to default values. The
   * resulting struct should be freed with avcodec_free_context().
   *
   * @param codec if non-NULL, allocate private data and initialize defaults
   *              for the given codec. It is illegal to then call avcodec_open2()
   *              with a different codec.
   *              If NULL, then the codec-specific defaults won't be initialized,
   *              which may result in suboptimal default settings (this is
   *              important mainly for encoders, e.g. libx264).
   *
   * @return An AVCodecContext filled with default values or NULL on failure.
   */
  AVCodecContext *avcodec_alloc_context3(const AVCodec *codec);
  
  /**
   * Free the codec context and everything associated with it and write NULL to
   * the provided pointer.
   */
  void avcodec_free_context(AVCodecContext **avctx);
  
  #if FF_API_GET_CONTEXT_DEFAULTS
  /**
   * @deprecated This function should not be used, as closing and opening a codec
   * context multiple time is not supported. A new codec context should be
   * allocated for each new use.
   */
  int avcodec_get_context_defaults3(AVCodecContext *s, const AVCodec *codec);
  #endif
  
  /**
   * Get the AVClass for AVCodecContext. It can be used in combination with
   * AV_OPT_SEARCH_FAKE_OBJ for examining options.
   *
   * @see av_opt_find().
   */
  const AVClass *avcodec_get_class(void);
  
  #if FF_API_GET_FRAME_CLASS
  /**
   * @deprecated This function should not be used.
   */
  attribute_deprecated
  const AVClass *avcodec_get_frame_class(void);
  #endif
  
  /**
   * Get the AVClass for AVSubtitleRect. It can be used in combination with
   * AV_OPT_SEARCH_FAKE_OBJ for examining options.
   *
   * @see av_opt_find().
   */
  const AVClass *avcodec_get_subtitle_rect_class(void);
  
  #if FF_API_COPY_CONTEXT
  /**
   * Copy the settings of the source AVCodecContext into the destination
   * AVCodecContext. The resulting destination codec context will be
   * unopened, i.e. you are required to call avcodec_open2() before you
   * can use this AVCodecContext to decode/encode video/audio data.
   *
   * @param dest target codec context, should be initialized with
   *             avcodec_alloc_context3(NULL), but otherwise uninitialized
   * @param src source codec context
   * @return AVERROR() on error (e.g. memory allocation error), 0 on success
   *
   * @deprecated The semantics of this function are ill-defined and it should not
   * be used. If you need to transfer the stream parameters from one codec context
   * to another, use an intermediate AVCodecParameters instance and the
   * avcodec_parameters_from_context() / avcodec_parameters_to_context()
   * functions.
   */
  attribute_deprecated
  int avcodec_copy_context(AVCodecContext *dest, const AVCodecContext *src);
  #endif
  
  /**
   * Fill the parameters struct based on the values from the supplied codec
   * context. Any allocated fields in par are freed and replaced with duplicates
   * of the corresponding fields in codec.
   *
   * @return >= 0 on success, a negative AVERROR code on failure
   */
  int avcodec_parameters_from_context(AVCodecParameters *par,
                                      const AVCodecContext *codec);
  
  /**
   * Fill the codec context based on the values from the supplied codec
   * parameters. Any allocated fields in codec that have a corresponding field in
   * par are freed and replaced with duplicates of the corresponding field in par.
   * Fields in codec that do not have a counterpart in par are not touched.
   *
   * @return >= 0 on success, a negative AVERROR code on failure.
   */
  int avcodec_parameters_to_context(AVCodecContext *codec,
                                    const AVCodecParameters *par);
  
  /**
   * Initialize the AVCodecContext to use the given AVCodec. Prior to using this
   * function the context has to be allocated with avcodec_alloc_context3().
   *
   * The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(),
   * avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for
   * retrieving a codec.
   *
   * @warning This function is not thread safe!
   *
   * @note Always call this function before using decoding routines (such as
   * @ref avcodec_receive_frame()).
   *
   * @code
   * av_dict_set(&opts, "b", "2.5M", 0);
   * codec = avcodec_find_decoder(AV_CODEC_ID_H264);
   * if (!codec)
   *     exit(1);
   *
   * context = avcodec_alloc_context3(codec);
   *
   * if (avcodec_open2(context, codec, opts) < 0)
   *     exit(1);
   * @endcode
   *
   * @param avctx The context to initialize.
   * @param codec The codec to open this context for. If a non-NULL codec has been
   *              previously passed to avcodec_alloc_context3() or
   *              for this context, then this parameter MUST be either NULL or
   *              equal to the previously passed codec.
   * @param options A dictionary filled with AVCodecContext and codec-private options.
   *                On return this object will be filled with options that were not found.
   *
   * @return zero on success, a negative value on error
   * @see avcodec_alloc_context3(), avcodec_find_decoder(), avcodec_find_encoder(),
   *      av_dict_set(), av_opt_find().
   */
  int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options);
  
  /**
   * Close a given AVCodecContext and free all the data associated with it
   * (but not the AVCodecContext itself).
   *
   * Calling this function on an AVCodecContext that hasn't been opened will free
   * the codec-specific data allocated in avcodec_alloc_context3() with a non-NULL
   * codec. Subsequent calls will do nothing.
   *
   * @note Do not use this function. Use avcodec_free_context() to destroy a
   * codec context (either open or closed). Opening and closing a codec context
   * multiple times is not supported anymore -- use multiple codec contexts
   * instead.
   */
  int avcodec_close(AVCodecContext *avctx);
  
  /**
   * Free all allocated data in the given subtitle struct.
   *
   * @param sub AVSubtitle to free.
   */
  void avsubtitle_free(AVSubtitle *sub);
  
  /**
   * @}
   */
  
  /**
   * @addtogroup lavc_decoding
   * @{
   */
  
  /**
   * The default callback for AVCodecContext.get_buffer2(). It is made public so
   * it can be called by custom get_buffer2() implementations for decoders without
   * AV_CODEC_CAP_DR1 set.
   */
  int avcodec_default_get_buffer2(AVCodecContext *s, AVFrame *frame, int flags);
  
  /**
   * The default callback for AVCodecContext.get_encode_buffer(). It is made public so
   * it can be called by custom get_encode_buffer() implementations for encoders without
   * AV_CODEC_CAP_DR1 set.
   */
  int avcodec_default_get_encode_buffer(AVCodecContext *s, AVPacket *pkt, int flags);
  
  /**
   * Modify width and height values so that they will result in a memory
   * buffer that is acceptable for the codec if you do not use any horizontal
   * padding.
   *
   * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
   */
  void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height);
  
  /**
   * Modify width and height values so that they will result in a memory
   * buffer that is acceptable for the codec if you also ensure that all
   * line sizes are a multiple of the respective linesize_align[i].
   *
   * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
   */
  void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
                                 int linesize_align[AV_NUM_DATA_POINTERS]);
  
  /**
   * Converts AVChromaLocation to swscale x/y chroma position.
   *
   * The positions represent the chroma (0,0) position in a coordinates system
   * with luma (0,0) representing the origin and luma(1,1) representing 256,256
   *
   * @param xpos  horizontal chroma sample position
   * @param ypos  vertical   chroma sample position
   */
  int avcodec_enum_to_chroma_pos(int *xpos, int *ypos, enum AVChromaLocation pos);
  
  /**
   * Converts swscale x/y chroma position to AVChromaLocation.
   *
   * The positions represent the chroma (0,0) position in a coordinates system
   * with luma (0,0) representing the origin and luma(1,1) representing 256,256
   *
   * @param xpos  horizontal chroma sample position
   * @param ypos  vertical   chroma sample position
   */
  enum AVChromaLocation avcodec_chroma_pos_to_enum(int xpos, int ypos);
  
  #if FF_API_OLD_ENCDEC
  /**
   * Decode the audio frame of size avpkt->size from avpkt->data into frame.
   *
   * Some decoders may support multiple frames in a single AVPacket. Such
   * decoders would then just decode the first frame and the return value would be
   * less than the packet size. In this case, avcodec_decode_audio4 has to be
   * called again with an AVPacket containing the remaining data in order to
   * decode the second frame, etc...  Even if no frames are returned, the packet
   * needs to be fed to the decoder with remaining data until it is completely
   * consumed or an error occurs.
   *
   * Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between input
   * and output. This means that for some packets they will not immediately
   * produce decoded output and need to be flushed at the end of decoding to get
   * all the decoded data. Flushing is done by calling this function with packets
   * with avpkt->data set to NULL and avpkt->size set to 0 until it stops
   * returning samples. It is safe to flush even those decoders that are not
   * marked with AV_CODEC_CAP_DELAY, then no samples will be returned.
   *
   * @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
   *          larger than the actual read bytes because some optimized bitstream
   *          readers read 32 or 64 bits at once and could read over the end.
   *
   * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
   * before packets may be fed to the decoder.
   *
   * @param      avctx the codec context
   * @param[out] frame The AVFrame in which to store decoded audio samples.
   *                   The decoder will allocate a buffer for the decoded frame by
   *                   calling the AVCodecContext.get_buffer2() callback.
   *                   When AVCodecContext.refcounted_frames is set to 1, the frame is
   *                   reference counted and the returned reference belongs to the
   *                   caller. The caller must release the frame using av_frame_unref()
   *                   when the frame is no longer needed. The caller may safely write
   *                   to the frame if av_frame_is_writable() returns 1.
   *                   When AVCodecContext.refcounted_frames is set to 0, the returned
   *                   reference belongs to the decoder and is valid only until the
   *                   next call to this function or until closing or flushing the
   *                   decoder. The caller may not write to it.
   * @param[out] got_frame_ptr Zero if no frame could be decoded, otherwise it is
   *                           non-zero. Note that this field being set to zero
   *                           does not mean that an error has occurred. For
   *                           decoders with AV_CODEC_CAP_DELAY set, no given decode
   *                           call is guaranteed to produce a frame.
   * @param[in]  avpkt The input AVPacket containing the input buffer.
   *                   At least avpkt->data and avpkt->size should be set. Some
   *                   decoders might also require additional fields to be set.
   * @return A negative error code is returned if an error occurred during
   *         decoding, otherwise the number of bytes consumed from the input
   *         AVPacket is returned.
   *
  * @deprecated Use avcodec_send_packet() and avcodec_receive_frame().
   */
  attribute_deprecated
  int avcodec_decode_audio4(AVCodecContext *avctx, AVFrame *frame,
                            int *got_frame_ptr, const AVPacket *avpkt);
  
  /**
   * Decode the video frame of size avpkt->size from avpkt->data into picture.
   * Some decoders may support multiple frames in a single AVPacket, such
   * decoders would then just decode the first frame.
   *
   * @warning The input buffer must be AV_INPUT_BUFFER_PADDING_SIZE larger than
   * the actual read bytes because some optimized bitstream readers read 32 or 64
   * bits at once and could read over the end.
   *
   * @warning The end of the input buffer buf should be set to 0 to ensure that
   * no overreading happens for damaged MPEG streams.
   *
   * @note Codecs which have the AV_CODEC_CAP_DELAY capability set have a delay
   * between input and output, these need to be fed with avpkt->data=NULL,
   * avpkt->size=0 at the end to return the remaining frames.
   *
   * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
   * before packets may be fed to the decoder.
   *
   * @param avctx the codec context
   * @param[out] picture The AVFrame in which the decoded video frame will be stored.
   *             Use av_frame_alloc() to get an AVFrame. The codec will
   *             allocate memory for the actual bitmap by calling the
   *             AVCodecContext.get_buffer2() callback.
   *             When AVCodecContext.refcounted_frames is set to 1, the frame is
   *             reference counted and the returned reference belongs to the
   *             caller. The caller must release the frame using av_frame_unref()
   *             when the frame is no longer needed. The caller may safely write
   *             to the frame if av_frame_is_writable() returns 1.
   *             When AVCodecContext.refcounted_frames is set to 0, the returned
   *             reference belongs to the decoder and is valid only until the
   *             next call to this function or until closing or flushing the
   *             decoder. The caller may not write to it.
   *
   * @param[in] avpkt The input AVPacket containing the input buffer.
   *            You can create such packet with av_init_packet() and by then setting
   *            data and size, some decoders might in addition need other fields like
   *            flags&AV_PKT_FLAG_KEY. All decoders are designed to use the least
   *            fields possible.
   * @param[in,out] got_picture_ptr Zero if no frame could be decompressed, otherwise, it is nonzero.
   * @return On error a negative value is returned, otherwise the number of bytes
   * used or zero if no frame could be decompressed.
   *
   * @deprecated Use avcodec_send_packet() and avcodec_receive_frame().
   */
  attribute_deprecated
  int avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture,
                           int *got_picture_ptr,
                           const AVPacket *avpkt);
  #endif
  
  /**
   * Decode a subtitle message.
   * Return a negative value on error, otherwise return the number of bytes used.
   * If no subtitle could be decompressed, got_sub_ptr is zero.
   * Otherwise, the subtitle is stored in *sub.
   * Note that AV_CODEC_CAP_DR1 is not available for subtitle codecs. This is for
   * simplicity, because the performance difference is expected to be negligible
   * and reusing a get_buffer written for video codecs would probably perform badly
   * due to a potentially very different allocation pattern.
   *
   * Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between input
   * and output. This means that for some packets they will not immediately
   * produce decoded output and need to be flushed at the end of decoding to get
   * all the decoded data. Flushing is done by calling this function with packets
   * with avpkt->data set to NULL and avpkt->size set to 0 until it stops
   * returning subtitles. It is safe to flush even those decoders that are not
   * marked with AV_CODEC_CAP_DELAY, then no subtitles will be returned.
   *
   * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
   * before packets may be fed to the decoder.
   *
   * @param avctx the codec context
   * @param[out] sub The preallocated AVSubtitle in which the decoded subtitle will be stored,
   *                 must be freed with avsubtitle_free if *got_sub_ptr is set.
   * @param[in,out] got_sub_ptr Zero if no subtitle could be decompressed, otherwise, it is nonzero.
   * @param[in] avpkt The input AVPacket containing the input buffer.
   */
  int avcodec_decode_subtitle2(AVCodecContext *avctx, AVSubtitle *sub,
                              int *got_sub_ptr,
                              AVPacket *avpkt);
  
  /**
   * Supply raw packet data as input to a decoder.
   *
   * Internally, this call will copy relevant AVCodecContext fields, which can
   * influence decoding per-packet, and apply them when the packet is actually
   * decoded. (For example AVCodecContext.skip_frame, which might direct the
   * decoder to drop the frame contained by the packet sent with this function.)
   *
   * @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
   *          larger than the actual read bytes because some optimized bitstream
   *          readers read 32 or 64 bits at once and could read over the end.
   *
   * @warning Do not mix this API with the legacy API (like avcodec_decode_video2())
   *          on the same AVCodecContext. It will return unexpected results now
   *          or in future include.libavcodec versions.
   *
   * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
   *       before packets may be fed to the decoder.
   *
   * @param avctx codec context
   * @param[in] avpkt The input AVPacket. Usually, this will be a single video
   *                  frame, or several complete audio frames.
   *                  Ownership of the packet remains with the caller, and the
   *                  decoder will not write to the packet. The decoder may create
   *                  a reference to the packet data (or copy it if the packet is
   *                  not reference-counted).
   *                  Unlike with older APIs, the packet is always fully consumed,
   *                  and if it contains multiple frames (e.g. some audio codecs),
   *                  will require you to call avcodec_receive_frame() multiple
   *                  times afterwards before you can send a new packet.
   *                  It can be NULL (or an AVPacket with data set to NULL and
   *                  size set to 0); in this case, it is considered a flush
   *                  packet, which signals the end of the stream. Sending the
   *                  first flush packet will return success. Subsequent ones are
   *                  unnecessary and will return AVERROR_EOF. If the decoder
   *                  still has frames buffered, it will return them after sending
   *                  a flush packet.
   *
   * @return 0 on success, otherwise negative error code:
   *      AVERROR(EAGAIN):   input is not accepted in the current state - user
   *                         must read output with avcodec_receive_frame() (once
   *                         all output is read, the packet should be resent, and
   *                         the call will not fail with EAGAIN).
   *      AVERROR_EOF:       the decoder has been flushed, and no new packets can
   *                         be sent to it (also returned if more than 1 flush
   *                         packet is sent)
   *      AVERROR(EINVAL):   codec not opened, it is an encoder, or requires flush
   *      AVERROR(ENOMEM):   failed to add packet to internal queue, or similar
   *      other errors: legitimate decoding errors
   */
  int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt);
  
  /**
   * Return decoded output data from a decoder.
   *
   * @param avctx codec context
   * @param frame This will be set to a reference-counted video or audio
   *              frame (depending on the decoder type) allocated by the
   *              decoder. Note that the function will always call
   *              av_frame_unref(frame) before doing anything else.
   *
   * @return
   *      0:                 success, a frame was returned
   *      AVERROR(EAGAIN):   output is not available in this state - user must try
   *                         to send new input
   *      AVERROR_EOF:       the decoder has been fully flushed, and there will be
   *                         no more output frames
   *      AVERROR(EINVAL):   codec not opened, or it is an encoder
   *      AVERROR_INPUT_CHANGED:   current decoded frame has changed parameters
   *                               with respect to first decoded frame. Applicable
   *                               when flag AV_CODEC_FLAG_DROPCHANGED is set.
   *      other negative values: legitimate decoding errors
   */
  int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);
  
  /**
   * Supply a raw video or audio frame to the encoder. Use avcodec_receive_packet()
   * to retrieve buffered output packets.
   *
   * @param avctx     codec context
   * @param[in] frame AVFrame containing the raw audio or video frame to be encoded.
   *                  Ownership of the frame remains with the caller, and the
   *                  encoder will not write to the frame. The encoder may create
   *                  a reference to the frame data (or copy it if the frame is
   *                  not reference-counted).
   *                  It can be NULL, in which case it is considered a flush
   *                  packet.  This signals the end of the stream. If the encoder
   *                  still has packets buffered, it will return them after this
   *                  call. Once flushing mode has been entered, additional flush
   *                  packets are ignored, and sending frames will return
   *                  AVERROR_EOF.
   *
   *                  For audio:
   *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
   *                  can have any number of samples.
   *                  If it is not set, frame->nb_samples must be equal to
   *                  avctx->frame_size for all frames except the last.
   *                  The final frame may be smaller than avctx->frame_size.
   * @return 0 on success, otherwise negative error code:
   *      AVERROR(EAGAIN):   input is not accepted in the current state - user
   *                         must read output with avcodec_receive_packet() (once
   *                         all output is read, the packet should be resent, and
   *                         the call will not fail with EAGAIN).
   *      AVERROR_EOF:       the encoder has been flushed, and no new frames can
   *                         be sent to it
   *      AVERROR(EINVAL):   codec not opened, refcounted_frames not set, it is a
   *                         decoder, or requires flush
   *      AVERROR(ENOMEM):   failed to add packet to internal queue, or similar
   *      other errors: legitimate encoding errors
   */
  int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame);
  
  /**
   * Read encoded data from the encoder.
   *
   * @param avctx codec context
   * @param avpkt This will be set to a reference-counted packet allocated by the
   *              encoder. Note that the function will always call
   *              av_packet_unref(avpkt) before doing anything else.
   * @return 0 on success, otherwise negative error code:
   *      AVERROR(EAGAIN):   output is not available in the current state - user
   *                         must try to send input
   *      AVERROR_EOF:       the encoder has been fully flushed, and there will be
   *                         no more output packets
   *      AVERROR(EINVAL):   codec not opened, or it is a decoder
   *      other errors: legitimate encoding errors
   */
  int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt);
  
  /**
   * Create and return a AVHWFramesContext with values adequate for hardware
   * decoding. This is meant to get called from the get_format callback, and is
   * a helper for preparing a AVHWFramesContext for AVCodecContext.hw_frames_ctx.
   * This API is for decoding with certain hardware acceleration modes/APIs only.
   *
   * The returned AVHWFramesContext is not initialized. The caller must do this
   * with av_hwframe_ctx_init().
   *
   * Calling this function is not a requirement, but makes it simpler to avoid
   * codec or hardware API specific details when manually allocating frames.
   *
   * Alternatively to this, an API user can set AVCodecContext.hw_device_ctx,
   * which sets up AVCodecContext.hw_frames_ctx fully automatically, and makes
   * it unnecessary to call this function or having to care about
   * AVHWFramesContext initialization at all.
   *
   * There are a number of requirements for calling this function:
   *
   * - It must be called from get_format with the same avctx parameter that was
   *   passed to get_format. Calling it outside of get_format is not allowed, and
   *   can trigger undefined behavior.
   * - The function is not always supported (see description of return values).
   *   Even if this function returns successfully, hwaccel initialization could
   *   fail later. (The degree to which implementations check whether the stream
   *   is actually supported varies. Some do this check only after the user's
   *   get_format callback returns.)
   * - The hw_pix_fmt must be one of the choices suggested by get_format. If the
   *   user decides to use a AVHWFramesContext prepared with this API function,
   *   the user must return the same hw_pix_fmt from get_format.
   * - The device_ref passed to this function must support the given hw_pix_fmt.
   * - After calling this API function, it is the user's responsibility to
   *   initialize the AVHWFramesContext (returned by the out_frames_ref parameter),
   *   and to set AVCodecContext.hw_frames_ctx to it. If done, this must be done
   *   before returning from get_format (this is implied by the normal
   *   AVCodecContext.hw_frames_ctx API rules).
   * - The AVHWFramesContext parameters may change every time time get_format is
   *   called. Also, AVCodecContext.hw_frames_ctx is reset before get_format. So
   *   you are inherently required to go through this process again on every
   *   get_format call.
   * - It is perfectly possible to call this function without actually using
   *   the resulting AVHWFramesContext. One use-case might be trying to reuse a
   *   previously initialized AVHWFramesContext, and calling this API function
   *   only to test whether the required frame parameters have changed.
   * - Fields that use dynamically allocated values of any kind must not be set
   *   by the user unless setting them is explicitly allowed by the documentation.
   *   If the user sets AVHWFramesContext.free and AVHWFramesContext.user_opaque,
   *   the new free callback must call the potentially set previous free callback.
   *   This API call may set any dynamically allocated fields, including the free
   *   callback.
   *
   * The function will set at least the following fields on AVHWFramesContext
   * (potentially more, depending on hwaccel API):
   *
   * - All fields set by av_hwframe_ctx_alloc().
   * - Set the format field to hw_pix_fmt.
   * - Set the sw_format field to the most suited and most versatile format. (An
   *   implication is that this will prefer generic formats over opaque formats
   *   with arbitrary restrictions, if possible.)
   * - Set the width/height fields to the coded frame size, rounded up to the
   *   API-specific minimum alignment.
   * - Only _if_ the hwaccel requires a pre-allocated pool: set the initial_pool_size
   *   field to the number of maximum reference surfaces possible with the codec,
   *   plus 1 surface for the user to work (meaning the user can safely reference
   *   at most 1 decoded surface at a time), plus additional buffering introduced
   *   by frame threading. If the hwaccel does not require pre-allocation, the
   *   field is left to 0, and the decoder will allocate new surfaces on demand
   *   during decoding.
   * - Possibly AVHWFramesContext.hwctx fields, depending on the underlying
   *   hardware API.
   *
   * Essentially, out_frames_ref returns the same as av_hwframe_ctx_alloc(), but
   * with basic frame parameters set.
   *
   * The function is stateless, and does not change the AVCodecContext or the
   * device_ref AVHWDeviceContext.
   *
   * @param avctx The context which is currently calling get_format, and which
   *              implicitly contains all state needed for filling the returned
   *              AVHWFramesContext properly.
   * @param device_ref A reference to the AVHWDeviceContext describing the device
   *                   which will be used by the hardware decoder.
   * @param hw_pix_fmt The hwaccel format you are going to return from get_format.
   * @param out_frames_ref On success, set to a reference to an _uninitialized_
   *                       AVHWFramesContext, created from the given device_ref.
   *                       Fields will be set to values required for decoding.
   *                       Not changed if an error is returned.
   * @return zero on success, a negative value on error. The following error codes
   *         have special semantics:
   *      AVERROR(ENOENT): the decoder does not support this functionality. Setup
   *                       is always manual, or it is a decoder which does not
   *                       support setting AVCodecContext.hw_frames_ctx at all,
   *                       or it is a software format.
   *      AVERROR(EINVAL): it is known that hardware decoding is not supported for
   *                       this configuration, or the device_ref is not supported
   *                       for the hwaccel referenced by hw_pix_fmt.
   */
  int avcodec_get_hw_frames_parameters(AVCodecContext *avctx,
                                       AVBufferRef *device_ref,
                                       enum AVPixelFormat hw_pix_fmt,
                                       AVBufferRef **out_frames_ref);
  
  
  
  /**
   * @defgroup lavc_parsing Frame parsing
   * @{
   */
  
  enum AVPictureStructure {
      AV_PICTURE_STRUCTURE_UNKNOWN,      //< unknown
      AV_PICTURE_STRUCTURE_TOP_FIELD,    //< coded as top field
      AV_PICTURE_STRUCTURE_BOTTOM_FIELD, //< coded as bottom field
      AV_PICTURE_STRUCTURE_FRAME,        //< coded as frame
  };
  
  typedef struct AVCodecParserContext {
      void *priv_data;
      struct AVCodecParser *parser;
      int64_t frame_offset; /* offset of the current frame */
      int64_t cur_offset; /* current offset
                             (incremented by each av_parser_parse()) */
      int64_t next_frame_offset; /* offset of the next frame */
      /* video info */
      int pict_type; /* XXX: Put it back in AVCodecContext. */
      /**
       * This field is used for proper frame duration computation in lavf.
       * It signals, how much longer the frame duration of the current frame
       * is compared to normal frame duration.
       *
       * frame_duration = (1 + repeat_pict) * time_base
       *
       * It is used by codecs like H.264 to display telecined material.
       */
      int repeat_pict; /* XXX: Put it back in AVCodecContext. */
      int64_t pts;     /* pts of the current frame */
      int64_t dts;     /* dts of the current frame */
  
      /* private data */
      int64_t last_pts;
      int64_t last_dts;
      int fetch_timestamp;
  
  #define AV_PARSER_PTS_NB 4
      int cur_frame_start_index;
      int64_t cur_frame_offset[AV_PARSER_PTS_NB];
      int64_t cur_frame_pts[AV_PARSER_PTS_NB];
      int64_t cur_frame_dts[AV_PARSER_PTS_NB];
  
      int flags;
  #define PARSER_FLAG_COMPLETE_FRAMES           0x0001
  #define PARSER_FLAG_ONCE                      0x0002
  /// Set if the parser has a valid file offset
  #define PARSER_FLAG_FETCHED_OFFSET            0x0004
  #define PARSER_FLAG_USE_CODEC_TS              0x1000
  
      int64_t offset;      ///< byte offset from starting packet start
      int64_t cur_frame_end[AV_PARSER_PTS_NB];
  
      /**
       * Set by parser to 1 for key frames and 0 for non-key frames.
       * It is initialized to -1, so if the parser doesn't set this flag,
       * old-style fallback using AV_PICTURE_TYPE_I picture type as key frames
       * will be used.
       */
      int key_frame;
  
  #if FF_API_CONVERGENCE_DURATION
      /**
       * @deprecated unused
       */
      attribute_deprecated
      int64_t convergence_duration;
  #endif
  
      // Timestamp generation support:
      /**
       * Synchronization point for start of timestamp generation.
       *
       * Set to >0 for sync point, 0 for no sync point and <0 for undefined
       * (default).
       *
       * For example, this corresponds to presence of H.264 buffering period
       * SEI message.
       */
      int dts_sync_point;
  
      /**
       * Offset of the current timestamp against last timestamp sync point in
       * units of AVCodecContext.time_base.
       *
       * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
       * contain a valid timestamp offset.
       *
       * Note that the timestamp of sync point has usually a nonzero
       * dts_ref_dts_delta, which refers to the previous sync point. Offset of
       * the next frame after timestamp sync point will be usually 1.
       *
       * For example, this corresponds to H.264 cpb_removal_delay.
       */
      int dts_ref_dts_delta;
  
      /**
       * Presentation delay of current frame in units of AVCodecContext.time_base.
       *
       * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
       * contain valid non-negative timestamp delta (presentation time of a frame
       * must not lie in the past).
       *
       * This delay represents the difference between decoding and presentation
       * time of the frame.
       *
       * For example, this corresponds to H.264 dpb_output_delay.
       */
      int pts_dts_delta;
  
      /**
       * Position of the packet in file.
       *
       * Analogous to cur_frame_pts/dts
       */
      int64_t cur_frame_pos[AV_PARSER_PTS_NB];
  
      /**
       * Byte position of currently parsed frame in stream.
       */
      int64_t pos;
  
      /**
       * Previous frame byte position.
       */
      int64_t last_pos;
  
      /**
       * Duration of the current frame.
       * For audio, this is in units of 1 / AVCodecContext.sample_rate.
       * For all other types, this is in units of AVCodecContext.time_base.
       */
      int duration;
  
      enum AVFieldOrder field_order;
  
      /**
       * Indicate whether a picture is coded as a frame, top field or bottom field.
       *
       * For example, H.264 field_pic_flag equal to 0 corresponds to
       * AV_PICTURE_STRUCTURE_FRAME. An H.264 picture with field_pic_flag
       * equal to 1 and bottom_field_flag equal to 0 corresponds to
       * AV_PICTURE_STRUCTURE_TOP_FIELD.
       */
      enum AVPictureStructure picture_structure;
  
      /**
       * Picture number incremented in presentation or output order.
       * This field may be reinitialized at the first picture of a new sequence.
       *
       * For example, this corresponds to H.264 PicOrderCnt.
       */
      int output_picture_number;
  
      /**
       * Dimensions of the decoded video intended for presentation.
       */
      int width;
      int height;
  
      /**
       * Dimensions of the coded video.
       */
      int coded_width;
      int coded_height;
  
      /**
       * The format of the coded data, corresponds to enum AVPixelFormat for video
       * and for enum AVSampleFormat for audio.
       *
       * Note that a decoder can have considerable freedom in how exactly it
       * decodes the data, so the format reported here might be different from the
       * one returned by a decoder.
       */
      int format;
  } AVCodecParserContext;
  
  typedef struct AVCodecParser {
      int codec_ids[5]; /* several codec IDs are permitted */
      int priv_data_size;
      int (*parser_init)(AVCodecParserContext *s);
      /* This callback never returns an error, a negative value means that
       * the frame start was in a previous packet. */
      int (*parser_parse)(AVCodecParserContext *s,
                          AVCodecContext *avctx,
                          const uint8_t **poutbuf, int *poutbuf_size,
                          const uint8_t *buf, int buf_size);
      void (*parser_close)(AVCodecParserContext *s);
      int (*split)(AVCodecContext *avctx, const uint8_t *buf, int buf_size);
  #if FF_API_NEXT
      attribute_deprecated
      struct AVCodecParser *next;
  #endif
  } AVCodecParser;
  
  /**
   * Iterate over all registered codec parsers.
   *
   * @param opaque a pointer where include.libavcodec will store the iteration state. Must
   *               point to NULL to start the iteration.
   *
   * @return the next registered codec parser or NULL when the iteration is
   *         finished
   */
  const AVCodecParser *av_parser_iterate(void **opaque);
  
  #if FF_API_NEXT
  attribute_deprecated
  AVCodecParser *av_parser_next(const AVCodecParser *c);
  
  attribute_deprecated
  void av_register_codec_parser(AVCodecParser *parser);
  #endif
  AVCodecParserContext *av_parser_init(int codec_id);
  
  /**
   * Parse a packet.
   *
   * @param s             parser context.
   * @param avctx         codec context.
   * @param poutbuf       set to pointer to parsed buffer or NULL if not yet finished.
   * @param poutbuf_size  set to size of parsed buffer or zero if not yet finished.
   * @param buf           input buffer.
   * @param buf_size      buffer size in bytes without the padding. I.e. the full buffer
                          size is assumed to be buf_size + AV_INPUT_BUFFER_PADDING_SIZE.
                          To signal EOF, this should be 0 (so that the last frame
                          can be output).
   * @param pts           input presentation timestamp.
   * @param dts           input decoding timestamp.
   * @param pos           input byte position in stream.
   * @return the number of bytes of the input bitstream used.
   *
   * Example:
   * @code
   *   while(in_len){
   *       len = av_parser_parse2(myparser, AVCodecContext, &data, &size,
   *                                        in_data, in_len,
   *                                        pts, dts, pos);
   *       in_data += len;
   *       in_len  -= len;
   *
   *       if(size)
   *          decode_frame(data, size);
   *   }
   * @endcode
   */
  int av_parser_parse2(AVCodecParserContext *s,
                       AVCodecContext *avctx,
                       uint8_t **poutbuf, int *poutbuf_size,
                       const uint8_t *buf, int buf_size,
                       int64_t pts, int64_t dts,
                       int64_t pos);
  
  #if FF_API_PARSER_CHANGE
  /**
   * @return 0 if the output buffer is a subset of the input, 1 if it is allocated and must be freed
   * @deprecated Use dump_extradata, remove_extra or extract_extradata
   *             bitstream filters instead.
   */
  attribute_deprecated
  int av_parser_change(AVCodecParserContext *s,
                       AVCodecContext *avctx,
                       uint8_t **poutbuf, int *poutbuf_size,
                       const uint8_t *buf, int buf_size, int keyframe);
  #endif
  void av_parser_close(AVCodecParserContext *s);
  
  /**
   * @}
   * @}
   */
  
  /**
   * @addtogroup lavc_encoding
   * @{
   */
  
  #if FF_API_OLD_ENCDEC
  /**
   * Encode a frame of audio.
   *
   * Takes input samples from frame and writes the next output packet, if
   * available, to avpkt. The output packet does not necessarily contain data for
   * the most recent frame, as encoders can delay, split, and combine input frames
   * internally as needed.
   *
   * @param avctx     codec context
   * @param avpkt     output AVPacket.
   *                  The user can supply an output buffer by setting
   *                  avpkt->data and avpkt->size prior to calling the
   *                  function, but if the size of the user-provided data is not
   *                  large enough, encoding will fail. If avpkt->data and
   *                  avpkt->size are set, avpkt->destruct must also be set. All
   *                  other AVPacket fields will be reset by the encoder using
   *                  av_init_packet(). If avpkt->data is NULL, the encoder will
   *                  allocate it. The encoder will set avpkt->size to the size
   *                  of the output packet.
   *
   *                  If this function fails or produces no output, avpkt will be
   *                  freed using av_packet_unref().
   * @param[in] frame AVFrame containing the raw audio data to be encoded.
   *                  May be NULL when flushing an encoder that has the
   *                  AV_CODEC_CAP_DELAY capability set.
   *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
   *                  can have any number of samples.
   *                  If it is not set, frame->nb_samples must be equal to
   *                  avctx->frame_size for all frames except the last.
   *                  The final frame may be smaller than avctx->frame_size.
   * @param[out] got_packet_ptr This field is set to 1 by include.libavcodec if the
   *                            output packet is non-empty, and to 0 if it is
   *                            empty. If the function returns an error, the
   *                            packet can be assumed to be invalid, and the
   *                            value of got_packet_ptr is undefined and should
   *                            not be used.
   * @return          0 on success, negative error code on failure
   *
   * @deprecated use avcodec_send_frame()/avcodec_receive_packet() instead.
   *             If allowed and required, set AVCodecContext.get_encode_buffer to
   *             a custom function to pass user supplied output buffers.
   */
  attribute_deprecated
  int avcodec_encode_audio2(AVCodecContext *avctx, AVPacket *avpkt,
                            const AVFrame *frame, int *got_packet_ptr);
  
  /**
   * Encode a frame of video.
   *
   * Takes input raw video data from frame and writes the next output packet, if
   * available, to avpkt. The output packet does not necessarily contain data for
   * the most recent frame, as encoders can delay and reorder input frames
   * internally as needed.
   *
   * @param avctx     codec context
   * @param avpkt     output AVPacket.
   *                  The user can supply an output buffer by setting
   *                  avpkt->data and avpkt->size prior to calling the
   *                  function, but if the size of the user-provided data is not
   *                  large enough, encoding will fail. All other AVPacket fields
   *                  will be reset by the encoder using av_init_packet(). If
   *                  avpkt->data is NULL, the encoder will allocate it.
   *                  The encoder will set avpkt->size to the size of the
   *                  output packet. The returned data (if any) belongs to the
   *                  caller, he is responsible for freeing it.
   *
   *                  If this function fails or produces no output, avpkt will be
   *                  freed using av_packet_unref().
   * @param[in] frame AVFrame containing the raw video data to be encoded.
   *                  May be NULL when flushing an encoder that has the
   *                  AV_CODEC_CAP_DELAY capability set.
   * @param[out] got_packet_ptr This field is set to 1 by include.libavcodec if the
   *                            output packet is non-empty, and to 0 if it is
   *                            empty. If the function returns an error, the
   *                            packet can be assumed to be invalid, and the
   *                            value of got_packet_ptr is undefined and should
   *                            not be used.
   * @return          0 on success, negative error code on failure
   *
   * @deprecated use avcodec_send_frame()/avcodec_receive_packet() instead.
   *             If allowed and required, set AVCodecContext.get_encode_buffer to
   *             a custom function to pass user supplied output buffers.
   */
  attribute_deprecated
  int avcodec_encode_video2(AVCodecContext *avctx, AVPacket *avpkt,
                            const AVFrame *frame, int *got_packet_ptr);
  #endif
  
  int avcodec_encode_subtitle(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                              const AVSubtitle *sub);
  
  
  /**
   * @}
   */
  
  #if FF_API_AVPICTURE
  /**
   * @addtogroup lavc_picture
   * @{
   */
  
  /**
   * @deprecated unused
   */
  attribute_deprecated
  int avpicture_alloc(AVPicture *picture, enum AVPixelFormat pix_fmt, int width, int height);
  
  /**
   * @deprecated unused
   */
  attribute_deprecated
  void avpicture_free(AVPicture *picture);
  
  /**
   * @deprecated use av_image_fill_arrays() instead.
   */
  attribute_deprecated
  int avpicture_fill(AVPicture *picture, const uint8_t *ptr,
                     enum AVPixelFormat pix_fmt, int width, int height);
  
  /**
   * @deprecated use av_image_copy_to_buffer() instead.
   */
  attribute_deprecated
  int avpicture_layout(const AVPicture *src, enum AVPixelFormat pix_fmt,
                       int width, int height,
                       unsigned char *dest, int dest_size);
  
  /**
   * @deprecated use av_image_get_buffer_size() instead.
   */
  attribute_deprecated
  int avpicture_get_size(enum AVPixelFormat pix_fmt, int width, int height);
  
  /**
   * @deprecated av_image_copy() instead.
   */
  attribute_deprecated
  void av_picture_copy(AVPicture *dst, const AVPicture *src,
                       enum AVPixelFormat pix_fmt, int width, int height);
  
  /**
   * @deprecated unused
   */
  attribute_deprecated
  int av_picture_crop(AVPicture *dst, const AVPicture *src,
                      enum AVPixelFormat pix_fmt, int top_band, int left_band);
  
  /**
   * @deprecated unused
   */
  attribute_deprecated
  int av_picture_pad(AVPicture *dst, const AVPicture *src, int height, int width, enum AVPixelFormat pix_fmt,
              int padtop, int padbottom, int padleft, int padright, int *color);
  
  /**
   * @}
   */
  #endif
  
  /**
   * @defgroup lavc_misc Utility functions
   * @ingroup libavc
   *
   * Miscellaneous utility functions related to both encoding and decoding
   * (or neither).
   * @{
   */
  
  /**
   * @defgroup lavc_misc_pixfmt Pixel formats
   *
   * Functions for working with pixel formats.
   * @{
   */
  
  #if FF_API_GETCHROMA
  /**
   * @deprecated Use av_pix_fmt_get_chroma_sub_sample
   */
  
  attribute_deprecated
  void avcodec_get_chroma_sub_sample(enum AVPixelFormat pix_fmt, int *h_shift, int *v_shift);
  #endif
  
  /**
   * Return a value representing the fourCC code associated to the
   * pixel format pix_fmt, or 0 if no associated fourCC code can be
   * found.
   */
  unsigned int avcodec_pix_fmt_to_codec_tag(enum AVPixelFormat pix_fmt);
  
  /**
   * Find the best pixel format to convert to given a certain source pixel
   * format.  When converting from one pixel format to another, information loss
   * may occur.  For example, when converting from RGB24 to GRAY, the color
   * information will be lost. Similarly, other losses occur when converting from
   * some formats to other formats. avcodec_find_best_pix_fmt_of_2() searches which of
   * the given pixel formats should be used to suffer the least amount of loss.
   * The pixel formats from which it chooses one, are determined by the
   * pix_fmt_list parameter.
   *
   *
   * @param[in] pix_fmt_list AV_PIX_FMT_NONE terminated array of pixel formats to choose from
   * @param[in] src_pix_fmt source pixel format
   * @param[in] has_alpha Whether the source pixel format alpha channel is used.
   * @param[out] loss_ptr Combination of flags informing you what kind of losses will occur.
   * @return The best pixel format to convert to or -1 if none was found.
   */
  enum AVPixelFormat avcodec_find_best_pix_fmt_of_list(const enum AVPixelFormat *pix_fmt_list,
                                              enum AVPixelFormat src_pix_fmt,
                                              int has_alpha, int *loss_ptr);
  
  #if FF_API_AVCODEC_PIX_FMT
  /**
   * @deprecated see av_get_pix_fmt_loss()
   */
  attribute_deprecated
  int avcodec_get_pix_fmt_loss(enum AVPixelFormat dst_pix_fmt, enum AVPixelFormat src_pix_fmt,
                               int has_alpha);
  /**
   * @deprecated see av_find_best_pix_fmt_of_2()
   */
  attribute_deprecated
  enum AVPixelFormat avcodec_find_best_pix_fmt_of_2(enum AVPixelFormat dst_pix_fmt1, enum AVPixelFormat dst_pix_fmt2,
                                              enum AVPixelFormat src_pix_fmt, int has_alpha, int *loss_ptr);
  
  attribute_deprecated
  enum AVPixelFormat avcodec_find_best_pix_fmt2(enum AVPixelFormat dst_pix_fmt1, enum AVPixelFormat dst_pix_fmt2,
                                              enum AVPixelFormat src_pix_fmt, int has_alpha, int *loss_ptr);
  #endif
  
  enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
  
  /**
   * @}
   */
  
  #if FF_API_TAG_STRING
  /**
   * Put a string representing the codec tag codec_tag in buf.
   *
   * @param buf       buffer to place codec tag in
   * @param buf_size size in bytes of buf
   * @param codec_tag codec tag to assign
   * @return the length of the string that would have been generated if
   * enough space had been available, excluding the trailing null
   *
   * @deprecated see av_fourcc_make_string() and av_fourcc2str().
   */
  attribute_deprecated
  size_t av_get_codec_tag_string(char *buf, size_t buf_size, unsigned int codec_tag);
  #endif
  
  void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode);
  
  /**
   * Return a name for the specified profile, if available.
   *
   * @param codec the codec that is searched for the given profile
   * @param profile the profile value for which a name is requested
   * @return A name for the profile if found, NULL otherwise.
   */
  const char *av_get_profile_name(const AVCodec *codec, int profile);
  
  /**
   * Return a name for the specified profile, if available.
   *
   * @param codec_id the ID of the codec to which the requested profile belongs
   * @param profile the profile value for which a name is requested
   * @return A name for the profile if found, NULL otherwise.
   *
   * @note unlike av_get_profile_name(), which searches a list of profiles
   *       supported by a specific decoder or encoder implementation, this
   *       function searches the list of profiles from the AVCodecDescriptor
   */
  const char *avcodec_profile_name(enum AVCodecID codec_id, int profile);
  
  int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2),void *arg, int *ret, int count, int size);
  int avcodec_default_execute2(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2, int, int),void *arg, int *ret, int count);
  //FIXME func typedef
  
  /**
   * Fill AVFrame audio data and linesize pointers.
   *
   * The buffer buf must be a preallocated buffer with a size big enough
   * to contain the specified samples amount. The filled AVFrame data
   * pointers will point to this buffer.
   *
   * AVFrame extended_data channel pointers are allocated if necessary for
   * planar audio.
   *
   * @param frame       the AVFrame
   *                    frame->nb_samples must be set prior to calling the
   *                    function. This function fills in frame->data,
   *                    frame->extended_data, frame->linesize[0].
   * @param nb_channels channel count
   * @param sample_fmt  sample format
   * @param buf         buffer to use for frame data
   * @param buf_size    size of buffer
   * @param align       plane size sample alignment (0 = default)
   * @return            >=0 on success, negative error code on failure
   * @todo return the size in bytes required to store the samples in
   * case of success, at the next include.libavutil bump
   */
  int avcodec_fill_audio_frame(AVFrame *frame, int nb_channels,
                               enum AVSampleFormat sample_fmt, const uint8_t *buf,
                               int buf_size, int align);
  
  /**
   * Reset the internal codec state / flush internal buffers. Should be called
   * e.g. when seeking or when switching to a different stream.
   *
   * @note for decoders, when refcounted frames are not used
   * (i.e. avctx->refcounted_frames is 0), this invalidates the frames previously
   * returned from the decoder. When refcounted frames are used, the decoder just
   * releases any references it might keep internally, but the caller's reference
   * remains valid.
   *
   * @note for encoders, this function will only do something if the encoder
   * declares support for AV_CODEC_CAP_ENCODER_FLUSH. When called, the encoder
   * will drain any remaining packets, and can then be re-used for a different
   * stream (as opposed to sending a null frame which will leave the encoder
   * in a permanent EOF state after draining). This can be desirable if the
   * cost of tearing down and replacing the encoder instance is high.
   */
  void avcodec_flush_buffers(AVCodecContext *avctx);
  
  /**
   * Return codec bits per sample.
   *
   * @param[in] codec_id the codec
   * @return Number of bits per sample or zero if unknown for the given codec.
   */
  int av_get_bits_per_sample(enum AVCodecID codec_id);
  
  /**
   * Return the PCM codec associated with a sample format.
   * @param be  endianness, 0 for little, 1 for big,
   *            -1 (or anything else) for native
   * @return  AV_CODEC_ID_PCM_* or AV_CODEC_ID_NONE
   */
  enum AVCodecID av_get_pcm_codec(enum AVSampleFormat fmt, int be);
  
  /**
   * Return codec bits per sample.
   * Only return non-zero if the bits per sample is exactly correct, not an
   * approximation.
   *
   * @param[in] codec_id the codec
   * @return Number of bits per sample or zero if unknown for the given codec.
   */
  int av_get_exact_bits_per_sample(enum AVCodecID codec_id);
  
  /**
   * Return audio frame duration.
   *
   * @param avctx        codec context
   * @param frame_bytes  size of the frame, or 0 if unknown
   * @return             frame duration, in samples, if known. 0 if not able to
   *                     determine.
   */
  int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes);
  
  /**
   * This function is the same as av_get_audio_frame_duration(), except it works
   * with AVCodecParameters instead of an AVCodecContext.
   */
  int av_get_audio_frame_duration2(AVCodecParameters *par, int frame_bytes);
  
  #if FF_API_OLD_BSF
  typedef struct AVBitStreamFilterContext {
      void *priv_data;
      const struct AVBitStreamFilter *filter;
      AVCodecParserContext *parser;
      struct AVBitStreamFilterContext *next;
      /**
       * Internal default arguments, used if NULL is passed to av_bitstream_filter_filter().
       * Not for access by library users.
       */
      char *args;
  } AVBitStreamFilterContext;
  
  /**
   * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
   * is deprecated. Use the new bitstream filtering API (using AVBSFContext).
   */
  attribute_deprecated
  void av_register_bitstream_filter(AVBitStreamFilter *bsf);
  /**
   * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
   * is deprecated. Use av_bsf_get_by_name(), av_bsf_alloc(), and av_bsf_init()
   * from the new bitstream filtering API (using AVBSFContext).
   */
  attribute_deprecated
  AVBitStreamFilterContext *av_bitstream_filter_init(const char *name);
  /**
   * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
   * is deprecated. Use av_bsf_send_packet() and av_bsf_receive_packet() from the
   * new bitstream filtering API (using AVBSFContext).
   */
  attribute_deprecated
  int av_bitstream_filter_filter(AVBitStreamFilterContext *bsfc,
                                 AVCodecContext *avctx, const char *args,
                                 uint8_t **poutbuf, int *poutbuf_size,
                                 const uint8_t *buf, int buf_size, int keyframe);
  /**
   * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
   * is deprecated. Use av_bsf_free() from the new bitstream filtering API (using
   * AVBSFContext).
   */
  attribute_deprecated
  void av_bitstream_filter_close(AVBitStreamFilterContext *bsf);
  /**
   * @deprecated the old bitstream filtering API (using AVBitStreamFilterContext)
   * is deprecated. Use av_bsf_iterate() from the new bitstream filtering API (using
   * AVBSFContext).
   */
  attribute_deprecated
  const AVBitStreamFilter *av_bitstream_filter_next(const AVBitStreamFilter *f);
  #endif
  
  #if FF_API_NEXT
  attribute_deprecated
  const AVBitStreamFilter *av_bsf_next(void **opaque);
  #endif
  
  /* memory */
  
  /**
   * Same behaviour av_fast_malloc but the buffer has additional
   * AV_INPUT_BUFFER_PADDING_SIZE at the end which will always be 0.
   *
   * In addition the whole buffer will initially and after resizes
   * be 0-initialized so that no uninitialized data will ever appear.
   */
  void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size);
  
  /**
   * Same behaviour av_fast_padded_malloc except that buffer will always
   * be 0-initialized after call.
   */
  void av_fast_padded_mallocz(void *ptr, unsigned int *size, size_t min_size);
  
  /**
   * Encode extradata length to a buffer. Used by xiph codecs.
   *
   * @param s buffer to write to; must be at least (v/255+1) bytes long
   * @param v size of extradata in bytes
   * @return number of bytes written to the buffer.
   */
  unsigned int av_xiphlacing(unsigned char *s, unsigned int v);
  
  #if FF_API_USER_VISIBLE_AVHWACCEL
  /**
   * Register the hardware accelerator hwaccel.
   *
   * @deprecated  This function doesn't do anything.
   */
  attribute_deprecated
  void av_register_hwaccel(AVHWAccel *hwaccel);
  
  /**
   * If hwaccel is NULL, returns the first registered hardware accelerator,
   * if hwaccel is non-NULL, returns the next registered hardware accelerator
   * after hwaccel, or NULL if hwaccel is the last one.
   *
   * @deprecated  AVHWaccel structures contain no user-serviceable parts, so
   *              this function should not be used.
   */
  attribute_deprecated
  AVHWAccel *av_hwaccel_next(const AVHWAccel *hwaccel);
  #endif
  
  #if FF_API_LOCKMGR
  /**
   * Lock operation used by lockmgr
   *
   * @deprecated Deprecated together with av_lockmgr_register().
   */
  enum AVLockOp {
    AV_LOCK_CREATE,  ///< Create a mutex
    AV_LOCK_OBTAIN,  ///< Lock the mutex
    AV_LOCK_RELEASE, ///< Unlock the mutex
    AV_LOCK_DESTROY, ///< Free mutex resources
  };
  
  /**
   * Register a user provided lock manager supporting the operations
   * specified by AVLockOp. The "mutex" argument to the function points
   * to a (void *) where the lockmgr should store/get a pointer to a user
   * allocated mutex. It is NULL upon AV_LOCK_CREATE and equal to the
   * value left by the last call for all other ops. If the lock manager is
   * unable to perform the op then it should leave the mutex in the same
   * state as when it was called and return a non-zero value. However,
   * when called with AV_LOCK_DESTROY the mutex will always be assumed to
   * have been successfully destroyed. If av_lockmgr_register succeeds
   * it will return a non-negative value, if it fails it will return a
   * negative value and destroy all mutex and unregister all callbacks.
   * av_lockmgr_register is not thread-safe, it must be called from a
   * single thread before any calls which make use of locking are used.
   *
   * @param cb User defined callback. av_lockmgr_register invokes calls
   *           to this callback and the previously registered callback.
   *           The callback will be used to create more than one mutex
   *           each of which must be backed by its own underlying locking
   *           mechanism (i.e. do not use a single static object to
   *           implement your lock manager). If cb is set to NULL the
   *           lockmgr will be unregistered.
   *
   * @deprecated This function does nothing, and always returns 0. Be sure to
   *             build with thread support to get basic thread safety.
   */
  attribute_deprecated
  int av_lockmgr_register(int (*cb)(void **mutex, enum AVLockOp op));
  #endif
  
  /**
   * @return a positive value if s is open (i.e. avcodec_open2() was called on it
   * with no corresponding avcodec_close()), 0 otherwise.
   */
  int avcodec_is_open(AVCodecContext *s);
  
  /**
   * Allocate a CPB properties structure and initialize its fields to default
   * values.
   *
   * @param size if non-NULL, the size of the allocated struct will be written
   *             here. This is useful for embedding it in side data.
   *
   * @return the newly allocated struct or NULL on failure
   */
  AVCPBProperties *av_cpb_properties_alloc(size_t *size);
  
  /**
   * @}
   */
  
  #endif /* AVCODEC_AVCODEC_H */
  