mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-24 08:12:44 +00:00
bad5537e2c
Otherwise doxygen complains about ambiguous filenames when files exist under the same name in different subdirectories. Originally committed as revision 16912 to svn://svn.ffmpeg.org/ffmpeg/trunk
105 lines
3.3 KiB
C
105 lines
3.3 KiB
C
/*
|
|
* 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 libavcodec/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));
|
|
}
|