text: /*
   * filter layer
   * Copyright (c) 2007 Bobby Bingham
   *
   * 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 AVFILTER_AVFILTER_H
  #define AVFILTER_AVFILTER_H
  
  /**
   * @file
   * @ingroup lavfi
   * Main libavfilter public API header
   */
  
  /**
   * @defgroup lavfi Libavfilter - graph-based frame editing library
   * @{
   */
  
  #include <stddef.h>
  
  #include "libavutil/attributes.h"
  #include "libavutil/avutil.h"
  #include "libavutil/dict.h"
  #include "libavutil/frame.h"
  #include "libavutil/log.h"
  #include "libavutil/samplefmt.h"
  #include "libavutil/pixfmt.h"
  #include "libavutil/rational.h"
  
  #include "libavfilter/version.h"
  
  /**
   * Return the LIBAVFILTER_VERSION_INT constant.
   */
  unsigned avfilter_version(void);
  
  /**
   * Return the libavfilter build-time configuration.
   */
  const char *avfilter_configuration(void);
  
  /**
   * Return the libavfilter license.
   */
  const char *avfilter_license(void);
  
  typedef struct AVFilterContext AVFilterContext;
  typedef struct AVFilterLink    AVFilterLink;
  typedef struct AVFilterPad     AVFilterPad;
  typedef struct AVFilterFormats AVFilterFormats;
  
  #if FF_API_AVFILTERBUFFER
  /**
   * A reference-counted buffer data type used by the filter system. Filters
   * should not store pointers to this structure directly, but instead use the
   * AVFilterBufferRef structure below.
   */
  typedef struct AVFilterBuffer {
      uint8_t *data[8];           ///< buffer data for each plane/channel
  
      /**
       * pointers to the data planes/channels.
       *
       * For video, this should simply point to data[].
       *
       * For planar audio, each channel has a separate data pointer, and
       * linesize[0] contains the size of each channel buffer.
       * For packed audio, there is just one data pointer, and linesize[0]
       * contains the total size of the buffer for all channels.
       *
       * Note: Both data and extended_data will always be set, but for planar
       * audio with more channels that can fit in data, extended_data must be used
       * in order to access all channels.
       */
      uint8_t **extended_data;
      int linesize[8];            ///< number of bytes per line
  
      /** private data to be used by a custom free function */
      void *priv;
      /**
       * A pointer to the function to deallocate this buffer if the default
       * function is not sufficient. This could, for example, add the memory
       * back into a memory pool to be reused later without the overhead of
       * reallocating it from scratch.
       */
      void (*free)(struct AVFilterBuffer *buf);
  
      int format;                 ///< media format
      int w, h;                   ///< width and height of the allocated buffer
      unsigned refcount;          ///< number of references to this buffer
  } AVFilterBuffer;
  
  #define AV_PERM_READ     0x01   ///< can read from the buffer
  #define AV_PERM_WRITE    0x02   ///< can write to the buffer
  #define AV_PERM_PRESERVE 0x04   ///< nobody else can overwrite the buffer
  #define AV_PERM_REUSE    0x08   ///< can output the buffer multiple times, with the same contents each time
  #define AV_PERM_REUSE2   0x10   ///< can output the buffer multiple times, modified each time
  #define AV_PERM_NEG_LINESIZES 0x20  ///< the buffer requested can have negative linesizes
  #define AV_PERM_ALIGN    0x40   ///< the buffer must be aligned
  
  #define AVFILTER_ALIGN 16 //not part of ABI
  
  /**
   * Audio specific properties in a reference to an AVFilterBuffer. Since
   * AVFilterBufferRef is common to different media formats, audio specific
   * per reference properties must be separated out.
   */
  typedef struct AVFilterBufferRefAudioProps {
      uint64_t channel_layout;    ///< channel layout of audio buffer
      int nb_samples;             ///< number of audio samples per channel
      int sample_rate;            ///< audio buffer sample rate
      int channels;               ///< number of channels (do not access directly)
  } AVFilterBufferRefAudioProps;
  
  /**
   * Video specific properties in a reference to an AVFilterBuffer. Since
   * AVFilterBufferRef is common to different media formats, video specific
   * per reference properties must be separated out.
   */
  typedef struct AVFilterBufferRefVideoProps {
      int w;                      ///< image width
      int h;                      ///< image height
      AVRational sample_aspect_ratio; ///< sample aspect ratio
      int interlaced;             ///< is frame interlaced
      int top_field_first;        ///< field order
      enum AVPictureType pict_type; ///< picture type of the frame
      int key_frame;              ///< 1 -> keyframe, 0-> not
      int qp_table_linesize;                ///< qp_table stride
      int qp_table_size;            ///< qp_table size
      int8_t *qp_table;             ///< array of Quantization Parameters
  } AVFilterBufferRefVideoProps;
  
  /**
   * A reference to an AVFilterBuffer. Since filters can manipulate the origin of
   * a buffer to, for example, crop image without any memcpy, the buffer origin
   * and dimensions are per-reference properties. Linesize is also useful for
   * image flipping, frame to field filters, etc, and so is also per-reference.
   *
   * TODO: add anything necessary for frame reordering
   */
  typedef struct AVFilterBufferRef {
      AVFilterBuffer *buf;        ///< the buffer that this is a reference to
      uint8_t *data[8];           ///< picture/audio data for each plane
      /**
       * pointers to the data planes/channels.
       *
       * For video, this should simply point to data[].
       *
       * For planar audio, each channel has a separate data pointer, and
       * linesize[0] contains the size of each channel buffer.
       * For packed audio, there is just one data pointer, and linesize[0]
       * contains the total size of the buffer for all channels.
       *
       * Note: Both data and extended_data will always be set, but for planar
       * audio with more channels that can fit in data, extended_data must be used
       * in order to access all channels.
       */
      uint8_t **extended_data;
      int linesize[8];            ///< number of bytes per line
  
      AVFilterBufferRefVideoProps *video; ///< video buffer specific properties
      AVFilterBufferRefAudioProps *audio; ///< audio buffer specific properties
  
      /**
       * presentation timestamp. The time unit may change during
       * filtering, as it is specified in the link and the filter code
       * may need to rescale the PTS accordingly.
       */
      int64_t pts;
      int64_t pos;                ///< byte position in stream, -1 if unknown
  
      int format;                 ///< media format
  
      int perms;                  ///< permissions, see the AV_PERM_* flags
  
      enum AVMediaType type;      ///< media type of buffer data
  
      AVDictionary *metadata;     ///< dictionary containing metadata key=value tags
  } AVFilterBufferRef;
  
  /**
   * Copy properties of src to dst, without copying the actual data
   */
  attribute_deprecated
  void avfilter_copy_buffer_ref_props(AVFilterBufferRef *dst, AVFilterBufferRef *src);
  
  /**
   * Add a new reference to a buffer.
   *
   * @param ref   an existing reference to the buffer
   * @param pmask a bitmask containing the allowable permissions in the new
   *              reference
   * @return      a new reference to the buffer with the same properties as the
   *              old, excluding any permissions denied by pmask
   */
  attribute_deprecated
  AVFilterBufferRef *avfilter_ref_buffer(AVFilterBufferRef *ref, int pmask);
  
  /**
   * Remove a reference to a buffer. If this is the last reference to the
   * buffer, the buffer itself is also automatically freed.
   *
   * @param ref reference to the buffer, may be NULL
   *
   * @note it is recommended to use avfilter_unref_bufferp() instead of this
   * function
   */
  attribute_deprecated
  void avfilter_unref_buffer(AVFilterBufferRef *ref);
  
  /**
   * Remove a reference to a buffer and set the pointer to NULL.
   * If this is the last reference to the buffer, the buffer itself
   * is also automatically freed.
   *
   * @param ref pointer to the buffer reference
   */
  attribute_deprecated
  void avfilter_unref_bufferp(AVFilterBufferRef **ref);
  #endif
  
  /**
   * Get the number of channels of a buffer reference.
   */
  attribute_deprecated
  int avfilter_ref_get_channels(AVFilterBufferRef *ref);
  
  #if FF_API_AVFILTERPAD_PUBLIC
  /**
   * A filter pad used for either input or output.
   *
   * See doc/filter_design.txt for details on how to implement the methods.
   *
   * @warning this struct might be removed from public API.
   * users should call avfilter_pad_get_name() and avfilter_pad_get_type()
   * to access the name and type fields; there should be no need to access
   * any other fields from outside of libavfilter.
   */
  struct AVFilterPad {
      /**
       * Pad name. The name is unique among inputs and among outputs, but an
       * input may have the same name as an output. This may be NULL if this
       * pad has no need to ever be referenced by name.
       */
      const char *name;
  
      /**
       * AVFilterPad type.
       */
      enum AVMediaType type;
  
      /**
       * Input pads:
       * Minimum required permissions on incoming buffers. Any buffer with
       * insufficient permissions will be automatically copied by the filter
       * system to a new buffer which provides the needed access permissions.
       *
       * Output pads:
       * Guaranteed permissions on outgoing buffers. Any buffer pushed on the
       * link must have at least these permissions; this fact is checked by
       * asserts. It can be used to optimize buffer allocation.
       */
      attribute_deprecated int min_perms;
  
      /**
       * Input pads:
       * Permissions which are not accepted on incoming buffers. Any buffer
       * which has any of these permissions set will be automatically copied
       * by the filter system to a new buffer which does not have those
       * permissions. This can be used to easily disallow buffers with
       * AV_PERM_REUSE.
       *
       * Output pads:
       * Permissions which are automatically removed on outgoing buffers. It
       * can be used to optimize buffer allocation.
       */
      attribute_deprecated int rej_perms;
  
      /**
       * @deprecated unused
       */
      int (*start_frame)(AVFilterLink *link, AVFilterBufferRef *picref);
  
      /**
       * Callback function to get a video buffer. If NULL, the filter system will
       * use ff_default_get_video_buffer().
       *
       * Input video pads only.
       */
      AVFrame *(*get_video_buffer)(AVFilterLink *link, int w, int h);
  
      /**
       * Callback function to get an audio buffer. If NULL, the filter system will
       * use ff_default_get_audio_buffer().
       *
       * Input audio pads only.
       */
      AVFrame *(*get_audio_buffer)(AVFilterLink *link, int nb_samples);
  
      /**
       * @deprecated unused
       */
      int (*end_frame)(AVFilterLink *link);
  
      /**
       * @deprecated unused
       */
      int (*draw_slice)(AVFilterLink *link, int y, int height, int slice_dir);
  
      /**
       * Filtering callback. This is where a filter receives a frame with
       * audio/video data and should do its processing.
       *
       * Input pads only.
       *
       * @return >= 0 on success, a negative AVERROR on error. This function
       * must ensure that frame is properly unreferenced on error if it
       * hasn't been passed on to another filter.
       */
      int (*filter_frame)(AVFilterLink *link, AVFrame *frame);
  
      /**
       * Frame poll callback. This returns the number of immediately available
       * samples. It should return a positive value if the next request_frame()
       * is guaranteed to return one frame (with no delay).
       *
       * Defaults to just calling the source poll_frame() method.
       *
       * Output pads only.
       */
      int (*poll_frame)(AVFilterLink *link);
  
      /**
       * Frame request callback. A call to this should result in at least one
       * frame being output over the given link. This should return zero on
       * success, and another value on error.
       * See ff_request_frame() for the error codes with a specific
       * meaning.
       *
       * Output pads only.
       */
      int (*request_frame)(AVFilterLink *link);
  
      /**
       * Link configuration callback.
       *
       * For output pads, this should set the following link properties:
       * video: width, height, sample_aspect_ratio, time_base
       * audio: sample_rate.
       *
       * This should NOT set properties such as format, channel_layout, etc which
       * are negotiated between filters by the filter system using the
       * query_formats() callback before this function is called.
       *
       * For input pads, this should check the properties of the link, and update
       * the filter's internal state as necessary.
       *
       * For both input and output pads, this should return zero on success,
       * and another value on error.
       */
      int (*config_props)(AVFilterLink *link);
  
      /**
       * The filter expects a fifo to be inserted on its input link,
       * typically because it has a delay.
       *
       * input pads only.
       */
      int needs_fifo;
  
      int needs_writable;
  };
  #endif
  
  /**
   * Get the number of elements in a NULL-terminated array of AVFilterPads (e.g.
   * AVFilter.inputs/outputs).
   */
  int avfilter_pad_count(const AVFilterPad *pads);
  
  /**
   * Get the name of an AVFilterPad.
   *
   * @param pads an array of AVFilterPads
   * @param pad_idx index of the pad in the array it; is the caller's
   *                responsibility to ensure the index is valid
   *
   * @return name of the pad_idx'th pad in pads
   */
  const char *avfilter_pad_get_name(const AVFilterPad *pads, int pad_idx);
  
  /**
   * Get the type of an AVFilterPad.
   *
   * @param pads an array of AVFilterPads
   * @param pad_idx index of the pad in the array; it is the caller's
   *                responsibility to ensure the index is valid
   *
   * @return type of the pad_idx'th pad in pads
   */
  enum AVMediaType avfilter_pad_get_type(const AVFilterPad *pads, int pad_idx);
  
  /**
   * The number of the filter inputs is not determined just by AVFilter.inputs.
   * The filter might add additional inputs during initialization depending on the
   * options supplied to it.
   */
  #define AVFILTER_FLAG_DYNAMIC_INPUTS        (1 << 0)
  /**
   * The number of the filter outputs is not determined just by AVFilter.outputs.
   * The filter might add additional outputs during initialization depending on
   * the options supplied to it.
   */
  #define AVFILTER_FLAG_DYNAMIC_OUTPUTS       (1 << 1)
  /**
   * The filter supports multithreading by splitting frames into multiple parts
   * and processing them concurrently.
   */
  #define AVFILTER_FLAG_SLICE_THREADS         (1 << 2)
  /**
   * Some filters support a generic "enable" expression option that can be used
   * to enable or disable a filter in the timeline. Filters supporting this
   * option have this flag set. When the enable expression is false, the default
   * no-op filter_frame() function is called in place of the filter_frame()
   * callback defined on each input pad, thus the frame is passed unchanged to
   * the next filters.
   */
  #define AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC  (1 << 16)
  /**
   * Same as AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC, except that the filter will
   * have its filter_frame() callback(s) called as usual even when the enable
   * expression is false. The filter will disable filtering within the
   * filter_frame() callback(s) itself, for example executing code depending on
   * the AVFilterContext->is_disabled value.
   */
  #define AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL (1 << 17)
  /**
   * Handy mask to test whether the filter supports or no the timeline feature
   * (internally or generically).
   */
  #define AVFILTER_FLAG_SUPPORT_TIMELINE (AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL)
  
  /**
   * Filter definition. This defines the pads a filter contains, and all the
   * callback functions used to interact with the filter.
   */
  typedef struct AVFilter {
      /**
       * Filter name. Must be non-NULL and unique among filters.
       */
      const char *name;
  
      /**
       * A description of the filter. May be NULL.
       *
       * You should use the NULL_IF_CONFIG_SMALL() macro to define it.
       */
      const char *description;
  
      /**
       * List of inputs, terminated by a zeroed element.
       *
       * NULL if there are no (static) inputs. Instances of filters with
       * AVFILTER_FLAG_DYNAMIC_INPUTS set may have more inputs than present in
       * this list.
       */
      const AVFilterPad *inputs;
      /**
       * List of outputs, terminated by a zeroed element.
       *
       * NULL if there are no (static) outputs. Instances of filters with
       * AVFILTER_FLAG_DYNAMIC_OUTPUTS set may have more outputs than present in
       * this list.
       */
      const AVFilterPad *outputs;
  
      /**
       * A class for the private data, used to declare filter private AVOptions.
       * This field is NULL for filters that do not declare any options.
       *
       * If this field is non-NULL, the first member of the filter private data
       * must be a pointer to AVClass, which will be set by libavfilter generic
       * code to this class.
       */
      const AVClass *priv_class;
  
      /**
       * A combination of AVFILTER_FLAG_*
       */
      int flags;
  
      /*****************************************************************
       * All fields below this line are not part of the public API. They
       * may not be used outside of libavfilter and can be changed and
       * removed at will.
       * New public fields should be added right above.
       *****************************************************************
       */
  
      /**
       * Filter initialization function.
       *
       * This callback will be called only once during the filter lifetime, after
       * all the options have been set, but before links between filters are
       * established and format negotiation is done.
       *
       * Basic filter initialization should be done here. Filters with dynamic
       * inputs and/or outputs should create those inputs/outputs here based on
       * provided options. No more changes to this filter's inputs/outputs can be
       * done after this callback.
       *
       * This callback must not assume that the filter links exist or frame
       * parameters are known.
       *
       * @ref AVFilter.uninit "uninit" is guaranteed to be called even if
       * initialization fails, so this callback does not have to clean up on
       * failure.
       *
       * @return 0 on success, a negative AVERROR on failure
       */
      int (*init)(AVFilterContext *ctx);
  
      /**
       * Should be set instead of @ref AVFilter.init "init" by the filters that
       * want to pass a dictionary of AVOptions to nested contexts that are
       * allocated during init.
       *
       * On return, the options dict should be freed and replaced with one that
       * contains all the options which could not be processed by this filter (or
       * with NULL if all the options were processed).
       *
       * Otherwise the semantics is the same as for @ref AVFilter.init "init".
       */
      int (*init_dict)(AVFilterContext *ctx, AVDictionary **options);
  
      /**
       * Filter uninitialization function.
       *
       * Called only once right before the filter is freed. Should deallocate any
       * memory held by the filter, release any buffer references, etc. It does
       * not need to deallocate the AVFilterContext.priv memory itself.
       *
       * This callback may be called even if @ref AVFilter.init "init" was not
       * called or failed, so it must be prepared to handle such a situation.
       */
      void (*uninit)(AVFilterContext *ctx);
  
      /**
       * Query formats supported by the filter on its inputs and outputs.
       *
       * This callback is called after the filter is initialized (so the inputs
       * and outputs are fixed), shortly before the format negotiation. This
       * callback may be called more than once.
       *
       * This callback must set AVFilterLink.out_formats on every input link and
       * AVFilterLink.in_formats on every output link to a list of pixel/sample
       * formats that the filter supports on that link. For audio links, this
       * filter must also set @ref AVFilterLink.in_samplerates "in_samplerates" /
       * @ref AVFilterLink.out_samplerates "out_samplerates" and
       * @ref AVFilterLink.in_channel_layouts "in_channel_layouts" /
       * @ref AVFilterLink.out_channel_layouts "out_channel_layouts" analogously.
       *
       * This callback may be NULL for filters with one input, in which case
       * libavfilter assumes that it supports all input formats and preserves
       * them on output.
       *
       * @return zero on success, a negative value corresponding to an
       * AVERROR code otherwise
       */
      int (*query_formats)(AVFilterContext *);
  
      int priv_size;      ///< size of private data to allocate for the filter
  
      /**
       * Used by the filter registration system. Must not be touched by any other
       * code.
       */
      struct AVFilter *next;
  
      /**
       * Make the filter instance process a command.
       *
       * @param cmd    the command to process, for handling simplicity all commands must be alphanumeric only
       * @param arg    the argument for the command
       * @param res    a buffer with size res_size where the filter(s) can return a response. This must not change when the command is not supported.
       * @param flags  if AVFILTER_CMD_FLAG_FAST is set and the command would be
       *               time consuming then a filter should treat it like an unsupported command
       *
       * @returns >=0 on success otherwise an error code.
       *          AVERROR(ENOSYS) on unsupported commands
       */
      int (*process_command)(AVFilterContext *, const char *cmd, const char *arg, char *res, int res_len, int flags);
  
      /**
       * Filter initialization function, alternative to the init()
       * callback. Args contains the user-supplied parameters, opaque is
       * used for providing binary data.
       */
      int (*init_opaque)(AVFilterContext *ctx, void *opaque);
  } AVFilter;
  
  /**
   * Process multiple parts of the frame concurrently.
   */
  #define AVFILTER_THREAD_SLICE (1 << 0)
  
  typedef struct AVFilterInternal AVFilterInternal;
  
  /** An instance of a filter */
  struct AVFilterContext {
      const AVClass *av_class;        ///< needed for av_log() and filters common options
  
      const AVFilter *filter;         ///< the AVFilter of which this is an instance
  
      char *name;                     ///< name of this filter instance
  
      AVFilterPad   *input_pads;      ///< array of input pads
      AVFilterLink **inputs;          ///< array of pointers to input links
  #if FF_API_FOO_COUNT
      attribute_deprecated unsigned input_count; ///< @deprecated use nb_inputs
  #endif
      unsigned    nb_inputs;          ///< number of input pads
  
      AVFilterPad   *output_pads;     ///< array of output pads
      AVFilterLink **outputs;         ///< array of pointers to output links
  #if FF_API_FOO_COUNT
      attribute_deprecated unsigned output_count; ///< @deprecated use nb_outputs
  #endif
      unsigned    nb_outputs;         ///< number of output pads
  
      void *priv;                     ///< private data for use by the filter
  
      struct AVFilterGraph *graph;    ///< filtergraph this filter belongs to
  
      /**
       * Type of multithreading being allowed/used. A combination of
       * AVFILTER_THREAD_* flags.
       *
       * May be set by the caller before initializing the filter to forbid some
       * or all kinds of multithreading for this filter. The default is allowing
       * everything.
       *
       * When the filter is initialized, this field is combined using bit AND with
       * AVFilterGraph.thread_type to get the final mask used for determining
       * allowed threading types. I.e. a threading type needs to be set in both
       * to be allowed.
       *
       * After the filter is initialzed, libavfilter sets this field to the
       * threading type that is actually used (0 for no multithreading).
       */
      int thread_type;
  
      /**
       * An opaque struct for libavfilter internal use.
       */
      AVFilterInternal *internal;
  
      struct AVFilterCommand *command_queue;
  
      char *enable_str;               ///< enable expression string
      void *enable;                   ///< parsed expression (AVExpr*)
      double *var_values;             ///< variable values for the enable expression
      int is_disabled;                ///< the enabled state from the last expression evaluation
  };
  
  /**
   * A link between two filters. This contains pointers to the source and
   * destination filters between which this link exists, and the indexes of
   * the pads involved. In addition, this link also contains the parameters
   * which have been negotiated and agreed upon between the filter, such as
   * image dimensions, format, etc.
   */
  struct AVFilterLink {
      AVFilterContext *src;       ///< source filter
      AVFilterPad *srcpad;        ///< output pad on the source filter
  
      AVFilterContext *dst;       ///< dest filter
      AVFilterPad *dstpad;        ///< input pad on the dest filter
  
      enum AVMediaType type;      ///< filter media type
  
      /* These parameters apply only to video */
      int w;                      ///< agreed upon image width
      int h;                      ///< agreed upon image height
      AVRational sample_aspect_ratio; ///< agreed upon sample aspect ratio
      /* These parameters apply only to audio */
      uint64_t channel_layout;    ///< channel layout of current buffer (see libavutil/channel_layout.h)
      int sample_rate;            ///< samples per second
  
      int format;                 ///< agreed upon media format
  
      /**
       * Define the time base used by the PTS of the frames/samples
       * which will pass through this link.
       * During the configuration stage, each filter is supposed to
       * change only the output timebase, while the timebase of the
       * input link is assumed to be an unchangeable property.
       */
      AVRational time_base;
  
      /*****************************************************************
       * All fields below this line are not part of the public API. They
       * may not be used outside of libavfilter and can be changed and
       * removed at will.
       * New public fields should be added right above.
       *****************************************************************
       */
      /**
       * Lists of formats and channel layouts supported by the input and output
       * filters respectively. These lists are used for negotiating the format
       * to actually be used, which will be loaded into the format and
       * channel_layout members, above, when chosen.
       *
       */
      AVFilterFormats *in_formats;
      AVFilterFormats *out_formats;
  
      /**
       * Lists of channel layouts and sample rates used for automatic
       * negotiation.
       */
      AVFilterFormats  *in_samplerates;
      AVFilterFormats *out_samplerates;
      struct AVFilterChannelLayouts  *in_channel_layouts;
      struct AVFilterChannelLayouts *out_channel_layouts;
  
      /**
       * Audio only, the destination filter sets this to a non-zero value to
       * request that buffers with the given number of samples should be sent to
       * it. AVFilterPad.needs_fifo must also be set on the corresponding input
       * pad.
       * Last buffer before EOF will be padded with silence.
       */
      int request_samples;
  
      /** stage of the initialization of the link properties (dimensions, etc) */
      enum {
          AVLINK_UNINIT = 0,      ///< not started
          AVLINK_STARTINIT,       ///< started, but incomplete
          AVLINK_INIT             ///< complete
      } init_state;
  
      struct AVFilterPool *pool;
  
      /**
       * Graph the filter belongs to.
       */
      struct AVFilterGraph *graph;
  
      /**
       * Current timestamp of the link, as defined by the most recent
       * frame(s), in AV_TIME_BASE units.
       */
      int64_t current_pts;
  
      /**
       * Index in the age array.
       */
      int age_index;
  
      /**
       * Frame rate of the stream on the link, or 1/0 if unknown;
       * if left to 0/0, will be automatically be copied from the first input
       * of the source filter if it exists.
       *
       * Sources should set it to the best estimation of the real frame rate.
       * Filters should update it if necessary depending on their function.
       * Sinks can use it to set a default output frame rate.
       * It is similar to the r_frame_rate field in AVStream.
       */
      AVRational frame_rate;
  
      /**
       * Buffer partially filled with samples to achieve a fixed/minimum size.
       */
      AVFrame *partial_buf;
  
      /**
       * Size of the partial buffer to allocate.
       * Must be between min_samples and max_samples.
       */
      int partial_buf_size;
  
      /**
       * Minimum number of samples to filter at once. If filter_frame() is
       * called with fewer samples, it will accumulate them in partial_buf.
       * This field and the related ones must not be changed after filtering
       * has started.
       * If 0, all related fields are ignored.
       */
      int min_samples;
  
      /**
       * Maximum number of samples to filter at once. If filter_frame() is
       * called with more samples, it will split them.
       */
      int max_samples;
  
      /**
       * The buffer reference currently being received across the link by the
       * destination filter. This is used internally by the filter system to
       * allow automatic copying of buffers which do not have sufficient
       * permissions for the destination. This should not be accessed directly
       * by the filters.
       */
      AVFilterBufferRef *cur_buf_copy;
  
      /**
       * True if the link is closed.
       * If set, all attemps of start_frame, filter_frame or request_frame
       * will fail with AVERROR_EOF, and if necessary the reference will be
       * destroyed.
       * If request_frame returns AVERROR_EOF, this flag is set on the
       * corresponding link.
       * It can be set also be set by either the source or the destination
       * filter.
       */
      int closed;
  
      /**
       * Number of channels.
       */
      int channels;
  
      /**
       * True if a frame is being requested on the link.
       * Used internally by the framework.
       */
      unsigned frame_requested;
  
      /**
       * Link processing flags.
       */
      unsigned flags;
  
      /**
       * Number of past frames sent through the link.
       */
      int64_t frame_count;
  };
  
  /**
   * Link two filters together.
   *
   * @param src    the source filter
   * @param srcpad index of the output pad on the source filter
   * @param dst    the destination filter
   * @param dstpad index of the input pad on the destination filter
   * @return       zero on success
   */
  int avfilter_link(AVFilterContext *src, unsigned srcpad,
                    AVFilterContext *dst, unsigned dstpad);
  
  /**
   * Free the link in *link, and set its pointer to NULL.
   */
  void avfilter_link_free(AVFilterLink **link);
  
  /**
   * Get the number of channels of a link.
   */
  int avfilter_link_get_channels(AVFilterLink *link);
  
  /**
   * Set the closed field of a link.
   */
  void avfilter_link_set_closed(AVFilterLink *link, int closed);
  
  /**
   * Negotiate the media format, dimensions, etc of all inputs to a filter.
   *
   * @param filter the filter to negotiate the properties for its inputs
   * @return       zero on successful negotiation
   */
  int avfilter_config_links(AVFilterContext *filter);
  
  #if FF_API_AVFILTERBUFFER
  /**
   * Create a buffer reference wrapped around an already allocated image
   * buffer.
   *
   * @param data pointers to the planes of the image to reference
   * @param linesize linesizes for the planes of the image to reference
   * @param perms the required access permissions
   * @param w the width of the image specified by the data and linesize arrays
   * @param h the height of the image specified by the data and linesize arrays
   * @param format the pixel format of the image specified by the data and linesize arrays
   */
  attribute_deprecated
  AVFilterBufferRef *
  avfilter_get_video_buffer_ref_from_arrays(uint8_t * const data[4], const int linesize[4], int perms,
                                            int w, int h, enum AVPixelFormat format);
  
  /**
   * Create an audio buffer reference wrapped around an already
   * allocated samples buffer.
   *
   * See avfilter_get_audio_buffer_ref_from_arrays_channels() for a version
   * that can handle unknown channel layouts.
   *
   * @param data           pointers to the samples plane buffers
   * @param linesize       linesize for the samples plane buffers
   * @param perms          the required access permissions
   * @param nb_samples     number of samples per channel
   * @param sample_fmt     the format of each sample in the buffer to allocate
   * @param channel_layout the channel layout of the buffer
   */
  attribute_deprecated
  AVFilterBufferRef *avfilter_get_audio_buffer_ref_from_arrays(uint8_t **data,
                                                               int linesize,
                                                               int perms,
                                                               int nb_samples,
                                                               enum AVSampleFormat sample_fmt,
                                                               uint64_t channel_layout);
  /**
   * Create an audio buffer reference wrapped around an already
   * allocated samples buffer.
   *
   * @param data           pointers to the samples plane buffers
   * @param linesize       linesize for the samples plane buffers
   * @param perms          the required access permissions
   * @param nb_samples     number of samples per channel
   * @param sample_fmt     the format of each sample in the buffer to allocate
   * @param channels       the number of channels of the buffer
   * @param channel_layout the channel layout of the buffer,
   *                       must be either 0 or consistent with channels
   */
  attribute_deprecated
  AVFilterBufferRef *avfilter_get_audio_buffer_ref_from_arrays_channels(uint8_t **data,
                                                                        int linesize,
                                                                        int perms,
                                                                        int nb_samples,
                                                                        enum AVSampleFormat sample_fmt,
                                                                        int channels,
                                                                        uint64_t channel_layout);
  
  #endif
  
  
  #define AVFILTER_CMD_FLAG_ONE   1 ///< Stop once a filter understood the command (for target=all for example), fast filters are favored automatically
  #define AVFILTER_CMD_FLAG_FAST  2 ///< Only execute command when its fast (like a video out that supports contrast adjustment in hw)
  
  /**
   * Make the filter instance process a command.
   * It is recommended to use avfilter_graph_send_command().
   */
  int avfilter_process_command(AVFilterContext *filter, const char *cmd, const char *arg, char *res, int res_len, int flags);
  
  /** Initialize the filter system. Register all builtin filters. */
  void avfilter_register_all(void);
  
  #if FF_API_OLD_FILTER_REGISTER
  /** Uninitialize the filter system. Unregister all filters. */
  attribute_deprecated
  void avfilter_uninit(void);
  #endif
  
  /**
   * Register a filter. This is only needed if you plan to use
   * avfilter_get_by_name later to lookup the AVFilter structure by name. A
   * filter can still by instantiated with avfilter_graph_alloc_filter even if it
   * is not registered.
   *
   * @param filter the filter to register
   * @return 0 if the registration was successful, a negative value
   * otherwise
   */
  int avfilter_register(AVFilter *filter);
  
  /**
   * Get a filter definition matching the given name.
   *
   * @param name the filter name to find
   * @return     the filter definition, if any matching one is registered.
   *             NULL if none found.
   */
  #if !FF_API_NOCONST_GET_NAME
  const
  #endif
  AVFilter *avfilter_get_by_name(const char *name);
  
  /**
   * Iterate over all registered filters.
   * @return If prev is non-NULL, next registered filter after prev or NULL if
   * prev is the last filter. If prev is NULL, return the first registered filter.
   */
  const AVFilter *avfilter_next(const AVFilter *prev);
  
  #if FF_API_OLD_FILTER_REGISTER
  /**
   * If filter is NULL, returns a pointer to the first registered filter pointer,
   * if filter is non-NULL, returns the next pointer after filter.
   * If the returned pointer points to NULL, the last registered filter
   * was already reached.
   * @deprecated use avfilter_next()
   */
  attribute_deprecated
  AVFilter **av_filter_next(AVFilter **filter);
  #endif
  
  #if FF_API_AVFILTER_OPEN
  /**
   * Create a filter instance.
   *
   * @param filter_ctx put here a pointer to the created filter context
   * on success, NULL on failure
   * @param filter    the filter to create an instance of
   * @param inst_name Name to give to the new instance. Can be NULL for none.
   * @return >= 0 in case of success, a negative error code otherwise
   * @deprecated use avfilter_graph_alloc_filter() instead
   */
  attribute_deprecated
  int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name);
  #endif
  
  
  #if FF_API_AVFILTER_INIT_FILTER
  /**
   * Initialize a filter.
   *
   * @param filter the filter to initialize
   * @param args   A string of parameters to use when initializing the filter.
   *               The format and meaning of this string varies by filter.
   * @param opaque Any extra non-string data needed by the filter. The meaning
   *               of this parameter varies by filter.
   * @return       zero on success
   */
  attribute_deprecated
  int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque);
  #endif
  
  /**
   * Initialize a filter with the supplied parameters.
   *
   * @param ctx  uninitialized filter context to initialize
   * @param args Options to initialize the filter with. This must be a
   *             ':'-separated list of options in the 'key=value' form.
   *             May be NULL if the options have been set directly using the
   *             AVOptions API or there are no options that need to be set.
   * @return 0 on success, a negative AVERROR on failure
   */
  int avfilter_init_str(AVFilterContext *ctx, const char *args);
  
  /**
   * Initialize a filter with the supplied dictionary of options.
   *
   * @param ctx     uninitialized filter context to initialize
   * @param options An AVDictionary filled with options for this filter. On
   *                return this parameter will be destroyed and replaced with
   *                a dict containing options that were not found. This dictionary
   *                must be freed by the caller.
   *                May be NULL, then this function is equivalent to
   *                avfilter_init_str() with the second parameter set to NULL.
   * @return 0 on success, a negative AVERROR on failure
   *
   * @note This function and avfilter_init_str() do essentially the same thing,
   * the difference is in manner in which the options are passed. It is up to the
   * calling code to choose whichever is more preferable. The two functions also
   * behave differently when some of the provided options are not declared as
   * supported by the filter. In such a case, avfilter_init_str() will fail, but
   * this function will leave those extra options in the options AVDictionary and
   * continue as usual.
   */
  int avfilter_init_dict(AVFilterContext *ctx, AVDictionary **options);
  
  /**
   * Free a filter context. This will also remove the filter from its
   * filtergraph's list of filters.
   *
   * @param filter the filter to free
   */
  void avfilter_free(AVFilterContext *filter);
  
  /**
   * Insert a filter in the middle of an existing link.
   *
   * @param link the link into which the filter should be inserted
   * @param filt the filter to be inserted
   * @param filt_srcpad_idx the input pad on the filter to connect
   * @param filt_dstpad_idx the output pad on the filter to connect
   * @return     zero on success
   */
  int avfilter_insert_filter(AVFilterLink *link, AVFilterContext *filt,
                             unsigned filt_srcpad_idx, unsigned filt_dstpad_idx);
  
  #if FF_API_AVFILTERBUFFER
  /**
   * Copy the frame properties of src to dst, without copying the actual
   * image data.
   *
   * @return 0 on success, a negative number on error.
   */
  attribute_deprecated
  int avfilter_copy_frame_props(AVFilterBufferRef *dst, const AVFrame *src);
  
  /**
   * Copy the frame properties and data pointers of src to dst, without copying
   * the actual data.
   *
   * @return 0 on success, a negative number on error.
   */
  attribute_deprecated
  int avfilter_copy_buf_props(AVFrame *dst, const AVFilterBufferRef *src);
  #endif
  
  /**
   * @return AVClass for AVFilterContext.
   *
   * @see av_opt_find().
   */
  const AVClass *avfilter_get_class(void);
  
  typedef struct AVFilterGraphInternal AVFilterGraphInternal;
  
  /**
   * A function pointer passed to the @ref AVFilterGraph.execute callback to be
   * executed multiple times, possibly in parallel.
   *
   * @param ctx the filter context the job belongs to
   * @param arg an opaque parameter passed through from @ref
   *            AVFilterGraph.execute
   * @param jobnr the index of the job being executed
   * @param nb_jobs the total number of jobs
   *
   * @return 0 on success, a negative AVERROR on error
   */
  typedef int (avfilter_action_func)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
  
  /**
   * A function executing multiple jobs, possibly in parallel.
   *
   * @param ctx the filter context to which the jobs belong
   * @param func the function to be called multiple times
   * @param arg the argument to be passed to func
   * @param ret a nb_jobs-sized array to be filled with return values from each
   *            invocation of func
   * @param nb_jobs the number of jobs to execute
   *
   * @return 0 on success, a negative AVERROR on error
   */
  typedef int (avfilter_execute_func)(AVFilterContext *ctx, avfilter_action_func *func,
                                      void *arg, int *ret, int nb_jobs);
  
  typedef struct AVFilterGraph {
      const AVClass *av_class;
  #if FF_API_FOO_COUNT
      attribute_deprecated
      unsigned filter_count_unused;
  #endif
      AVFilterContext **filters;
  #if !FF_API_FOO_COUNT
      unsigned nb_filters;
  #endif
  
      char *scale_sws_opts; ///< sws options to use for the auto-inserted scale filters
      char *resample_lavr_opts;   ///< libavresample options to use for the auto-inserted resample filters
  #if FF_API_FOO_COUNT
      unsigned nb_filters;
  #endif
  
      /**
       * Type of multithreading allowed for filters in this graph. A combination
       * of AVFILTER_THREAD_* flags.
       *
       * May be set by the caller at any point, the setting will apply to all
       * filters initialized after that. The default is allowing everything.
       *
       * When a filter in this graph is initialized, this field is combined using
       * bit AND with AVFilterContext.thread_type to get the final mask used for
       * determining allowed threading types. I.e. a threading type needs to be
       * set in both to be allowed.
       */
      int thread_type;
  
      /**
       * Maximum number of threads used by filters in this graph. May be set by
       * the caller before adding any filters to the filtergraph. Zero (the
       * default) means that the number of threads is determined automatically.
       */
      int nb_threads;
  
      /**
       * Opaque object for libavfilter internal use.
       */
      AVFilterGraphInternal *internal;
  
      /**
       * Opaque user data. May be set by the caller to an arbitrary value, e.g. to
       * be used from callbacks like @ref AVFilterGraph.execute.
       * Libavfilter will not touch this field in any way.
       */
      void *opaque;
  
      /**
       * This callback may be set by the caller immediately after allocating the
       * graph and before adding any filters to it, to provide a custom
       * multithreading implementation.
       *
       * If set, filters with slice threading capability will call this callback
       * to execute multiple jobs in parallel.
       *
       * If this field is left unset, libavfilter will use its internal
       * implementation, which may or may not be multithreaded depending on the
       * platform and build options.
       */
      avfilter_execute_func *execute;
  
      char *aresample_swr_opts; ///< swr options to use for the auto-inserted aresample filters, Access ONLY through AVOptions
  
      /**
       * Private fields
       *
       * The following fields are for internal use only.
       * Their type, offset, number and semantic can change without notice.
       */
  
      AVFilterLink **sink_links;
      int sink_links_count;
  
      unsigned disable_auto_convert;
  } AVFilterGraph;
  
  /**
   * Allocate a filter graph.
   */
  AVFilterGraph *avfilter_graph_alloc(void);
  
  /**
   * Create a new filter instance in a filter graph.
   *
   * @param graph graph in which the new filter will be used
   * @param filter the filter to create an instance of
   * @param name Name to give to the new instance (will be copied to
   *             AVFilterContext.name). This may be used by the caller to identify
   *             different filters, libavfilter itself assigns no semantics to
   *             this parameter. May be NULL.
   *
   * @return the context of the newly created filter instance (note that it is
   *         also retrievable directly through AVFilterGraph.filters or with
   *         avfilter_graph_get_filter()) on success or NULL or failure.
   */
  AVFilterContext *avfilter_graph_alloc_filter(AVFilterGraph *graph,
                                               const AVFilter *filter,
                                               const char *name);
  
  /**
   * Get a filter instance with name name from graph.
   *
   * @return the pointer to the found filter instance or NULL if it
   * cannot be found.
   */
  AVFilterContext *avfilter_graph_get_filter(AVFilterGraph *graph, char *name);
  
  #if FF_API_AVFILTER_OPEN
  /**
   * Add an existing filter instance to a filter graph.
   *
   * @param graphctx  the filter graph
   * @param filter the filter to be added
   *
   * @deprecated use avfilter_graph_alloc_filter() to allocate a filter in a
   * filter graph
   */
  attribute_deprecated
  int avfilter_graph_add_filter(AVFilterGraph *graphctx, AVFilterContext *filter);
  #endif
  
  /**
   * Create and add a filter instance into an existing graph.
   * The filter instance is created from the filter filt and inited
   * with the parameters args and opaque.
   *
   * In case of success put in *filt_ctx the pointer to the created
   * filter instance, otherwise set *filt_ctx to NULL.
   *
   * @param name the instance name to give to the created filter instance
   * @param graph_ctx the filter graph
   * @return a negative AVERROR error code in case of failure, a non
   * negative value otherwise
   */
  int avfilter_graph_create_filter(AVFilterContext **filt_ctx, const AVFilter *filt,
                                   const char *name, const char *args, void *opaque,
                                   AVFilterGraph *graph_ctx);
  
  /**
   * Enable or disable automatic format conversion inside the graph.
   *
   * Note that format conversion can still happen inside explicitly inserted
   * scale and aresample filters.
   *
   * @param flags  any of the AVFILTER_AUTO_CONVERT_* constants
   */
  void avfilter_graph_set_auto_convert(AVFilterGraph *graph, unsigned flags);
  
  enum {
      AVFILTER_AUTO_CONVERT_ALL  =  0, /**< all automatic conversions enabled */
      AVFILTER_AUTO_CONVERT_NONE = -1, /**< all automatic conversions disabled */
  };
  
  /**
   * Check validity and configure all the links and formats in the graph.
   *
   * @param graphctx the filter graph
   * @param log_ctx context used for logging
   * @return >= 0 in case of success, a negative AVERROR code otherwise
   */
  int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx);
  
  /**
   * Free a graph, destroy its links, and set *graph to NULL.
   * If *graph is NULL, do nothing.
   */
  void avfilter_graph_free(AVFilterGraph **graph);
  
  /**
   * A linked-list of the inputs/outputs of the filter chain.
   *
   * This is mainly useful for avfilter_graph_parse() / avfilter_graph_parse2(),
   * where it is used to communicate open (unlinked) inputs and outputs from and
   * to the caller.
   * This struct specifies, per each not connected pad contained in the graph, the
   * filter context and the pad index required for establishing a link.
   */
  typedef struct AVFilterInOut {
      /** unique name for this input/output in the list */
      char *name;
  
      /** filter context associated to this input/output */
      AVFilterContext *filter_ctx;
  
      /** index of the filt_ctx pad to use for linking */
      int pad_idx;
  
      /** next input/input in the list, NULL if this is the last */
      struct AVFilterInOut *next;
  } AVFilterInOut;
  
  /**
   * Allocate a single AVFilterInOut entry.
   * Must be freed with avfilter_inout_free().
   * @return allocated AVFilterInOut on success, NULL on failure.
   */
  AVFilterInOut *avfilter_inout_alloc(void);
  
  /**
   * Free the supplied list of AVFilterInOut and set *inout to NULL.
   * If *inout is NULL, do nothing.
   */
  void avfilter_inout_free(AVFilterInOut **inout);
  
  #if AV_HAVE_INCOMPATIBLE_LIBAV_ABI || !FF_API_OLD_GRAPH_PARSE
  /**
   * Add a graph described by a string to a graph.
   *
   * @note The caller must provide the lists of inputs and outputs,
   * which therefore must be known before calling the function.
   *
   * @note The inputs parameter describes inputs of the already existing
   * part of the graph; i.e. from the point of view of the newly created
   * part, they are outputs. Similarly the outputs parameter describes
   * outputs of the already existing filters, which are provided as
   * inputs to the parsed filters.
   *
   * @param graph   the filter graph where to link the parsed grap context
   * @param filters string to be parsed
   * @param inputs  linked list to the inputs of the graph
   * @param outputs linked list to the outputs of the graph
   * @return zero on success, a negative AVERROR code on error
   */
  int avfilter_graph_parse(AVFilterGraph *graph, const char *filters,
                           AVFilterInOut *inputs, AVFilterInOut *outputs,
                           void *log_ctx);
  #else
  /**
   * Add a graph described by a string to a graph.
   *
   * @param graph   the filter graph where to link the parsed graph context
   * @param filters string to be parsed
   * @param inputs  pointer to a linked list to the inputs of the graph, may be NULL.
   *                If non-NULL, *inputs is updated to contain the list of open inputs
   *                after the parsing, should be freed with avfilter_inout_free().
   * @param outputs pointer to a linked list to the outputs of the graph, may be NULL.
   *                If non-NULL, *outputs is updated to contain the list of open outputs
   *                after the parsing, should be freed with avfilter_inout_free().
   * @return non negative on success, a negative AVERROR code on error
   * @deprecated Use avfilter_graph_parse_ptr() instead.
   */
  attribute_deprecated
  int avfilter_graph_parse(AVFilterGraph *graph, const char *filters,
                           AVFilterInOut **inputs, AVFilterInOut **outputs,
                           void *log_ctx);
  #endif
  
  /**
   * Add a graph described by a string to a graph.
   *
   * @param graph   the filter graph where to link the parsed graph context
   * @param filters string to be parsed
   * @param inputs  pointer to a linked list to the inputs of the graph, may be NULL.
   *                If non-NULL, *inputs is updated to contain the list of open inputs
   *                after the parsing, should be freed with avfilter_inout_free().
   * @param outputs pointer to a linked list to the outputs of the graph, may be NULL.
   *                If non-NULL, *outputs is updated to contain the list of open outputs
   *                after the parsing, should be freed with avfilter_inout_free().
   * @return non negative on success, a negative AVERROR code on error
   */
  int avfilter_graph_parse_ptr(AVFilterGraph *graph, const char *filters,
                               AVFilterInOut **inputs, AVFilterInOut **outputs,
                               void *log_ctx);
  
  /**
   * Add a graph described by a string to a graph.
   *
   * @param[in]  graph   the filter graph where to link the parsed graph context
   * @param[in]  filters string to be parsed
   * @param[out] inputs  a linked list of all free (unlinked) inputs of the
   *                     parsed graph will be returned here. It is to be freed
   *                     by the caller using avfilter_inout_free().
   * @param[out] outputs a linked list of all free (unlinked) outputs of the
   *                     parsed graph will be returned here. It is to be freed by the
   *                     caller using avfilter_inout_free().
   * @return zero on success, a negative AVERROR code on error
   *
   * @note This function returns the inputs and outputs that are left
   * unlinked after parsing the graph and the caller then deals with
   * them.
   * @note This function makes no reference whatsoever to already
   * existing parts of the graph and the inputs parameter will on return
   * contain inputs of the newly parsed part of the graph.  Analogously
   * the outputs parameter will contain outputs of the newly created
   * filters.
   */
  int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,
                            AVFilterInOut **inputs,
                            AVFilterInOut **outputs);
  
  /**
   * Send a command to one or more filter instances.
   *
   * @param graph  the filter graph
   * @param target the filter(s) to which the command should be sent
   *               "all" sends to all filters
   *               otherwise it can be a filter or filter instance name
   *               which will send the command to all matching filters.
   * @param cmd    the command to send, for handling simplicity all commands must be alphanumeric only
   * @param arg    the argument for the command
   * @param res    a buffer with size res_size where the filter(s) can return a response.
   *
   * @returns >=0 on success otherwise an error code.
   *              AVERROR(ENOSYS) on unsupported commands
   */
  int avfilter_graph_send_command(AVFilterGraph *graph, const char *target, const char *cmd, const char *arg, char *res, int res_len, int flags);
  
  /**
   * Queue a command for one or more filter instances.
   *
   * @param graph  the filter graph
   * @param target the filter(s) to which the command should be sent
   *               "all" sends to all filters
   *               otherwise it can be a filter or filter instance name
   *               which will send the command to all matching filters.
   * @param cmd    the command to sent, for handling simplicity all commands must be alphanummeric only
   * @param arg    the argument for the command
   * @param ts     time at which the command should be sent to the filter
   *
   * @note As this executes commands after this function returns, no return code
   *       from the filter is provided, also AVFILTER_CMD_FLAG_ONE is not supported.
   */
  int avfilter_graph_queue_command(AVFilterGraph *graph, const char *target, const char *cmd, const char *arg, int flags, double ts);
  
  
  /**
   * Dump a graph into a human-readable string representation.
   *
   * @param graph    the graph to dump
   * @param options  formatting options; currently ignored
   * @return  a string, or NULL in case of memory allocation failure;
   *          the string must be freed using av_free
   */
  char *avfilter_graph_dump(AVFilterGraph *graph, const char *options);
  
  /**
   * Request a frame on the oldest sink link.
   *
   * If the request returns AVERROR_EOF, try the next.
   *
   * Note that this function is not meant to be the sole scheduling mechanism
   * of a filtergraph, only a convenience function to help drain a filtergraph
   * in a balanced way under normal circumstances.
   *
   * Also note that AVERROR_EOF does not mean that frames did not arrive on
   * some of the sinks during the process.
   * When there are multiple sink links, in case the requested link
   * returns an EOF, this may cause a filter to flush pending frames
   * which are sent to another sink link, although unrequested.
   *
   * @return  the return value of ff_request_frame(),
   *          or AVERROR_EOF if all links returned AVERROR_EOF
   */
  int avfilter_graph_request_oldest(AVFilterGraph *graph);
  
  /**
   * @}
   */
  
  #endif /* AVFILTER_AVFILTER_H */
  