blob: e5f917d495d0bbf405b16ed7228df41517861220 [file] [log] [blame]
* 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
* 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
#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 purposely 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 & AV_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);