/* * 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 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); #endif /* AVCODEC_PSYMODEL_H */