ffmpeg/libavcodec/psymodel.h

   1 /*
   2  * audio encoder psychoacoustic model
   3  * Copyright (C) 2008 Konstantin Shishkov
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #ifndef AVCODEC_PSYMODEL_H
  23 #define AVCODEC_PSYMODEL_H
  24
  25 #include "avcodec.h"
  26
  27 /** maximum possible number of bands */
  28 #define PSY_MAX_BANDS 128
  29 /** maximum number of channels */
  30 #define PSY_MAX_CHANS 20
  31
  32 #define AAC_CUTOFF(s) ((s)->bit_rate ? FFMIN3(4000 + (s)->bit_rate/8, 12000 + (s)->bit_rate/32, (s)->sample_rate / 2) : ((s)->sample_rate / 2))
  33
  34 /**
  35  * single band psychoacoustic information
  36  */
  37 typedef struct FFPsyBand {
  38     int   bits;
  39     float energy;
  40     float threshold;
  41     float distortion;
  42     float perceptual_weight;
  43 } FFPsyBand;
  44
  45 /**
  46  * single channel psychoacoustic information
  47  */
  48 typedef struct FFPsyChannel {
  49     FFPsyBand psy_bands[PSY_MAX_BANDS]; ///< channel bands information
  50     float     entropy;                  ///< total PE for this channel
  51 } FFPsyChannel;
  52
  53 /**
  54  * psychoacoustic information for an arbitrary group of channels
  55  */
  56 typedef struct FFPsyChannelGroup {
  57     FFPsyChannel *ch[PSY_MAX_CHANS];  ///< pointers to the individual channels in the group
  58     uint8_t num_ch;                   ///< number of channels in this group
  59     uint8_t coupling[PSY_MAX_BANDS];  ///< allow coupling for this band in the group
  60 } FFPsyChannelGroup;
  61
  62 /**
  63  * windowing related information
  64  */
  65 typedef struct FFPsyWindowInfo {
  66     int window_type[3];               ///< window type (short/long/transitional, etc.) - current, previous and next
  67     int window_shape;                 ///< window shape (sine/KBD/whatever)
  68     int num_windows;                  ///< number of windows in a frame
  69     int grouping[8];                  ///< window grouping (for e.g. AAC)
  70     int *window_sizes;                ///< sequence of window sizes inside one frame (for eg. WMA)
  71 } FFPsyWindowInfo;
  72
  73 /**
  74  * context used by psychoacoustic model
  75  */
  76 typedef struct FFPsyContext {
  77     AVCodecContext *avctx;            ///< encoder context
  78     const struct FFPsyModel *model;   ///< encoder-specific model functions
  79
  80     FFPsyChannel      *ch;            ///< single channel information
  81     FFPsyChannelGroup *group;         ///< channel group information
  82     int num_groups;                   ///< number of channel groups
  83
  84     uint8_t **bands;                  ///< scalefactor band sizes for possible frame sizes
  85     int     *num_bands;               ///< number of scalefactor bands for possible frame sizes
  86     int num_lens;                     ///< number of scalefactor band sets
  87
  88     struct {
  89         int size;                     ///< size of the bitresevoir in bits
  90         int bits;                     ///< number of bits used in the bitresevoir
  91     } bitres;
  92
  93     void* model_priv_data;            ///< psychoacoustic model implementation private data
  94 } FFPsyContext;
  95
  96 /**
  97  * codec-specific psychoacoustic model implementation
  98  */
  99 typedef struct FFPsyModel {
 100     const char *name;
 101     int  (*init)   (FFPsyContext *apc);
 102
 103     /**
 104      * Suggest window sequence for channel.
 105      *
 106      * @param ctx       model context
 107      * @param audio     samples for the current frame
 108      * @param la        lookahead samples (NULL when unavailable)
 109      * @param channel   number of channel element to analyze
 110      * @param prev_type previous window type
 111      *
 112      * @return suggested window information in a structure
 113      */
 114     FFPsyWindowInfo (*window)(FFPsyContext *ctx, const float *audio, const float *la, int channel, int prev_type);
 115
 116     /**
 117      * Perform psychoacoustic analysis and set band info (threshold, energy) for a group of channels.
 118      *
 119      * @param ctx      model context
 120      * @param channel  channel number of the first channel in the group to perform analysis on
 121      * @param coeffs   array of pointers to the transformed coefficients
 122      * @param wi       window information for the channels in the group
 123      */
 124     void (*analyze)(FFPsyContext *ctx, int channel, const float **coeffs, const FFPsyWindowInfo *wi);
 125
 126     void (*end)    (FFPsyContext *apc);
 127 } FFPsyModel;
 128
 129 /**
 130  * Initialize psychoacoustic model.
 131  *
 132  * @param ctx        model context
 133  * @param avctx      codec context
 134  * @param num_lens   number of possible frame lengths
 135  * @param bands      scalefactor band lengths for all frame lengths
 136  * @param num_bands  number of scalefactor bands for all frame lengths
 137  * @param num_groups number of channel groups
 138  * @param group_map  array with # of channels in group - 1, for each group
 139  *
 140  * @return zero if successful, a negative value if not
 141  */
 142 int ff_psy_init(FFPsyContext *ctx, AVCodecContext *avctx, int num_lens,
 143                 const uint8_t **bands, const int *num_bands,
 144                 int num_groups, const uint8_t *group_map);
 145
 146 /**
 147  * Determine what group a channel belongs to.
 148  *
 149  * @param ctx     psymodel context
 150  * @param channel channel to locate the group for
 151  *
 152  * @return pointer to the FFPsyChannelGroup this channel belongs to
 153  */
 154 FFPsyChannelGroup *ff_psy_find_group(FFPsyContext *ctx, int channel);
 155
 156 /**
 157  * Cleanup model context at the end.
 158  *
 159  * @param ctx model context
 160  */
 161 void ff_psy_end(FFPsyContext *ctx);
 162
 163
 164 /**************************************************************************
 165  *                       Audio preprocessing stuff.                       *
 166  *       This should be moved into some audio filter eventually.          *
 167  **************************************************************************/
 168 struct FFPsyPreprocessContext;
 169
 170 /**
 171  * psychoacoustic model audio preprocessing initialization
 172  */
 173 struct FFPsyPreprocessContext *ff_psy_preprocess_init(AVCodecContext *avctx);
 174
 175 /**
 176  * Preprocess several channel in audio frame in order to compress it better.
 177  *
 178  * @param ctx      preprocessing context
 179  * @param audio    samples to be filtered (in place)
 180  * @param channels number of channel to preprocess
 181  */
 182 void ff_psy_preprocess(struct FFPsyPreprocessContext *ctx, float **audio, int channels);
 183
 184 /**
 185  * Cleanup audio preprocessing module.
 186  */
 187 void ff_psy_preprocess_end(struct FFPsyPreprocessContext *ctx);
 188
 189 #endif /* AVCODEC_PSYMODEL_H */