text: /*
   * audio encoder psychoacoustic model
   * Copyright (C) 2008 Konstantin Shishkov
   *
   * 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_PSYMODEL_H
  #define AVCODEC_PSYMODEL_H
  
  #include "avcodec.h"
  
  /** maximum possible number of bands */
  #define PSY_MAX_BANDS 128
  /** maximum number of channels */
  #define PSY_MAX_CHANS 20
  
  /* cutoff for VBR is purposedly increased, since LP filtering actually
   * hinders VBR performance rather than the opposite
   */
  #define AAC_CUTOFF_FROM_BITRATE(bit_rate,channels,sample_rate) (bit_rate ? FFMIN3(FFMIN3( \
      FFMAX(bit_rate/channels/5, bit_rate/channels*15/32 - 5500), \
      3000 + bit_rate/channels/4, \
      12000 + bit_rate/channels/16), \
      22000, \
      sample_rate / 2): (sample_rate / 2))
  #define AAC_CUTOFF(s) ( \
      (s->flags & CODEC_FLAG_QSCALE) \
      ? s->sample_rate / 2 \
      : AAC_CUTOFF_FROM_BITRATE(s->bit_rate, s->channels, s->sample_rate) \
  )
  
  /**
   * single band psychoacoustic information
   */
  typedef struct FFPsyBand {
      int   bits;
      float energy;
      float threshold;
      float spread;    /* Energy spread over the band */
  } FFPsyBand;
  
  /**
   * single channel psychoacoustic information
   */
  typedef struct FFPsyChannel {
      FFPsyBand psy_bands[PSY_MAX_BANDS]; ///< channel bands information
      float     entropy;                  ///< total PE for this channel
  } FFPsyChannel;
  
  /**
   * psychoacoustic information for an arbitrary group of channels
   */
  typedef struct FFPsyChannelGroup {
      FFPsyChannel *ch[PSY_MAX_CHANS];  ///< pointers to the individual channels in the group
      uint8_t num_ch;                   ///< number of channels in this group
      uint8_t coupling[PSY_MAX_BANDS];  ///< allow coupling for this band in the group
  } FFPsyChannelGroup;
  
  /**
   * windowing related information
   */
  typedef struct FFPsyWindowInfo {
      int window_type[3];               ///< window type (short/long/transitional, etc.) - current, previous and next
      int window_shape;                 ///< window shape (sine/KBD/whatever)
      int num_windows;                  ///< number of windows in a frame
      int grouping[8];                  ///< window grouping (for e.g. AAC)
      float clipping[8];                ///< maximum absolute normalized intensity in the given window for clip avoidance
      int *window_sizes;                ///< sequence of window sizes inside one frame (for eg. WMA)
  } FFPsyWindowInfo;
  
  /**
   * context used by psychoacoustic model
   */
  typedef struct FFPsyContext {
      AVCodecContext *avctx;            ///< encoder context
      const struct FFPsyModel *model;   ///< encoder-specific model functions
  
      FFPsyChannel      *ch;            ///< single channel information
      FFPsyChannelGroup *group;         ///< channel group information
      int num_groups;                   ///< number of channel groups
      int cutoff;                       ///< lowpass frequency cutoff for analysis
  
      uint8_t **bands;                  ///< scalefactor band sizes for possible frame sizes
      int     *num_bands;               ///< number of scalefactor bands for possible frame sizes
      int num_lens;                     ///< number of scalefactor band sets
  
      struct {
          int size;                     ///< size of the bitresevoir in bits
          int bits;                     ///< number of bits used in the bitresevoir
          int alloc;                    ///< number of bits allocated by the psy, or -1 if no allocation was done
      } bitres;
  
      void* model_priv_data;            ///< psychoacoustic model implementation private data
  } FFPsyContext;
  
  /**
   * codec-specific psychoacoustic model implementation
   */
  typedef struct FFPsyModel {
      const char *name;
      int  (*init)   (FFPsyContext *apc);
  
      /**
       * Suggest window sequence for channel.
       *
       * @param ctx       model context
       * @param audio     samples for the current frame
       * @param la        lookahead samples (NULL when unavailable)
       * @param channel   number of channel element to analyze
       * @param prev_type previous window type
       *
       * @return suggested window information in a structure
       */
      FFPsyWindowInfo (*window)(FFPsyContext *ctx, const float *audio, const float *la, int channel, int prev_type);
  
      /**
       * Perform psychoacoustic analysis and set band info (threshold, energy) for a group of channels.
       *
       * @param ctx      model context
       * @param channel  channel number of the first channel in the group to perform analysis on
       * @param coeffs   array of pointers to the transformed coefficients
       * @param wi       window information for the channels in the group
       */
      void (*analyze)(FFPsyContext *ctx, int channel, const float **coeffs, const FFPsyWindowInfo *wi);
  
      void (*end)    (FFPsyContext *apc);
  } FFPsyModel;
  
  /**
   * Initialize psychoacoustic model.
   *
   * @param ctx        model context
   * @param avctx      codec context
   * @param num_lens   number of possible frame lengths
   * @param bands      scalefactor band lengths for all frame lengths
   * @param num_bands  number of scalefactor bands for all frame lengths
   * @param num_groups number of channel groups
   * @param group_map  array with # of channels in group - 1, for each group
   *
   * @return zero if successful, a negative value if not
   */
  int ff_psy_init(FFPsyContext *ctx, AVCodecContext *avctx, int num_lens,
                  const uint8_t **bands, const int *num_bands,
                  int num_groups, const uint8_t *group_map);
  
  /**
   * Determine what group a channel belongs to.
   *
   * @param ctx     psymodel context
   * @param channel channel to locate the group for
   *
   * @return pointer to the FFPsyChannelGroup this channel belongs to
   */
  FFPsyChannelGroup *ff_psy_find_group(FFPsyContext *ctx, int channel);
  
  /**
   * Cleanup model context at the end.
   *
   * @param ctx model context
   */
  void ff_psy_end(FFPsyContext *ctx);
  
  
  /**************************************************************************
   *                       Audio preprocessing stuff.                       *
   *       This should be moved into some audio filter eventually.          *
   **************************************************************************/
  struct FFPsyPreprocessContext;
  
  /**
   * psychoacoustic model audio preprocessing initialization
   */
  struct FFPsyPreprocessContext *ff_psy_preprocess_init(AVCodecContext *avctx);
  
  /**
   * Preprocess several channel in audio frame in order to compress it better.
   *
   * @param ctx      preprocessing context
   * @param audio    samples to be filtered (in place)
   * @param channels number of channel to preprocess
   */
  void ff_psy_preprocess(struct FFPsyPreprocessContext *ctx, float **audio, int channels);
  
  /**
   * Cleanup audio preprocessing module.
   */
  void ff_psy_preprocess_end(struct FFPsyPreprocessContext *ctx);
  
  #endif /* AVCODEC_PSYMODEL_H */
  