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| -rw-r--r-- | libavcodec/aacpsy.c | 104 | ||||
| -rw-r--r-- | libavcodec/aacpsy.h | 50 |
2 files changed, 154 insertions, 0 deletions
diff --git a/libavcodec/aacpsy.c b/libavcodec/aacpsy.c new file mode 100644 index 0000000000..5a8a8522e9 --- /dev/null +++ b/libavcodec/aacpsy.c @@ -0,0 +1,104 @@ +/* + * AAC 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 + */ + +/** + * @file aacpsy.c + * AAC encoder psychoacoustic model + */ + +#include "avcodec.h" +#include "aacpsy.h" +#include "aactab.h" + +/*********************************** + * TODOs: + * General: + * better audio preprocessing (add DC highpass filter?) + * more psy models + * maybe improve coefficient quantization function in some way + * + * 3GPP-based psy model: + * thresholds linearization after their modifications for attaining given bitrate + * try other bitrate controlling mechanism (maybe use ratecontrol.c?) + * control quality for quality-based output + **********************************/ + +/** + * Quantize one coefficient. + * @return absolute value of the quantized coefficient + * @see 3GPP TS26.403 5.6.2 "Scalefactor determination" + */ +static av_always_inline int quant(float coef, const float Q) +{ + return av_clip((int)(pow(fabsf(coef) * Q, 0.75) + 0.4054), 0, 8191); +} + +static inline float get_approximate_quant_error(float *c, int size, int scale_idx) +{ + int i; + int q; + float coef, unquant, sum = 0.0f; + const float Q = ff_aac_pow2sf_tab[200 - scale_idx + SCALE_ONE_POS - SCALE_DIV_512]; + const float IQ = ff_aac_pow2sf_tab[200 + scale_idx - SCALE_ONE_POS + SCALE_DIV_512]; + for(i = 0; i < size; i++){ + coef = fabs(c[i]); + q = quant(c[i], Q); + unquant = (q * cbrt(q)) * IQ; + sum += (coef - unquant) * (coef - unquant); + } + return sum; +} + +/** + * constants for 3GPP AAC psychoacoustic model + * @{ + */ +#define PSY_3GPP_SPREAD_LOW 1.5f // spreading factor for ascending threshold spreading (15 dB/Bark) +#define PSY_3GPP_SPREAD_HI 3.0f // spreading factor for descending threshold spreading (30 dB/Bark) +/** + * @} + */ + +/** + * information for single band used by 3GPP TS26.403-inspired psychoacoustic model + */ +typedef struct Psy3gppBand{ + float energy; ///< band energy + float ffac; ///< form factor +}Psy3gppBand; + +/** + * psychoacoustic model frame type-dependent coefficients + */ +typedef struct Psy3gppCoeffs{ + float ath [64]; ///< absolute threshold of hearing per bands + float barks [64]; ///< Bark value for each spectral band in long frame + float spread_low[64]; ///< spreading factor for low-to-high threshold spreading in long frame + float spread_hi [64]; ///< spreading factor for high-to-low threshold spreading in long frame +}Psy3gppCoeffs; + +/** + * Calculate Bark value for given line. + */ +static inline float calc_bark(float f) +{ + return 13.3f * atanf(0.00076f * f) + 3.5f * atanf((f / 7500.0f) * (f / 7500.0f)); +} diff --git a/libavcodec/aacpsy.h b/libavcodec/aacpsy.h new file mode 100644 index 0000000000..d0dbb078e9 --- /dev/null +++ b/libavcodec/aacpsy.h @@ -0,0 +1,50 @@ +/* + * AAC 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 FFMPEG_AACPSY_H +#define FFMPEG_AACPSY_H + +#include "avcodec.h" +#include "aac.h" +#include "lowpass.h" + +enum AACPsyModelType{ + AAC_PSY_TEST, ///< a sample model to exercise encoder + AAC_PSY_3GPP, ///< model following recommendations from 3GPP TS 26.403 + + AAC_NB_PSY_MODELS ///< total number of psychoacoustic models, since it's not a part of the ABI new models can be added freely +}; + +/** + * context used by psychoacoustic model + */ +typedef struct AACPsyContext { + AVCodecContext *avctx; ///< encoder context +}AACPsyContext; + +/** + * Cleanup model context at the end. + * + * @param ctx model context + */ +void ff_aac_psy_end(AACPsyContext *ctx); + +#endif /* FFMPEG_AACPSY_H */ |