mirror of
https://github.com/cookiengineer/audacity
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134 lines
4.1 KiB
C
134 lines
4.1 KiB
C
/*
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* TwoLAME: an optimized MPEG Audio Layer Two encoder
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*
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* Copyright (C) 2001-2004 Michael Cheng
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* Copyright (C) 2004-2006 The TwoLAME Project
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* $Id$
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*
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*/
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#include <stdio.h>
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#include <math.h>
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#include "twolame.h"
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#include "common.h"
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#include "ath.h"
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#include "mem.h"
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#include "psycho_0.h"
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/* MFC Mar 03
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It's almost obscene how well this psycho model works for the amount of
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computational effort that's put in.
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I got the idea from:
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Hyen-O Oh et al "Low power mpeg audio encoders using simplified psychoacoustic model
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and fast bit allocation"
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IEEE Trans on Consumer Electronics v47 n3 August 2001. p613
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All this model does is look at the lowest ATH value within the subband, and then looks
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at the scalefactors. It combines the two in a real dodgy way to get the SMRs.
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Although the output values aren't really close to any of the other psycho models,
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the spread of values and the relative sizes of the values for the different subbands
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is about right
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Feel free to make any sort of generic change you want. Add or subtract numbers, take
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logs, whatever. Fiddle with the numbers until we get a good SMR output */
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static psycho_0_mem *psycho_0_init(twolame_options * glopts, int sfreq)
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{
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FLOAT freqperline = (FLOAT) sfreq / 1024.0;
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psycho_0_mem *mem = (psycho_0_mem *) TWOLAME_MALLOC(sizeof(psycho_0_mem));
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int sb, i;
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for (sb = 0; sb < SBLIMIT; sb++) {
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mem->ath_min[sb] = 1000; /* set it huge */
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}
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/* Find the minimum ATH in each subband */
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for (i = 0; i < 512; i++) {
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FLOAT thisfreq = i * freqperline;
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FLOAT ath_val = ath_db(thisfreq, 0);
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if (ath_val < mem->ath_min[i >> 4])
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mem->ath_min[i >> 4] = ath_val;
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}
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return mem;
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}
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void psycho_0(twolame_options * glopts, FLOAT SMR[2][SBLIMIT], unsigned int scalar[2][3][SBLIMIT])
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{
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psycho_0_mem *mem;
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int nch = glopts->num_channels_out;
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int sfreq = glopts->samplerate_out;
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int ch, sb, gr;
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unsigned int minscaleindex[2][SBLIMIT]; /* Smaller scale indexes mean bigger scalefactors */
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if (!glopts->p0mem) {
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glopts->p0mem = psycho_0_init(glopts, sfreq);
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}
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mem = glopts->p0mem;
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/* call functions for critical boundaries, freq. */
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if (!glopts->p0mem) { /* bands, bark values, and mapping */
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} else {
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mem = glopts->p0mem;
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}
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/* Find the minimum scalefactor index for each ch/sb */
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for (ch = 0; ch < nch; ch++)
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for (sb = 0; sb < SBLIMIT; sb++)
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minscaleindex[ch][sb] = scalar[ch][0][sb];
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for (ch = 0; ch < nch; ch++)
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for (gr = 1; gr < 3; gr++)
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for (sb = 0; sb < SBLIMIT; sb++)
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if (minscaleindex[ch][sb] > scalar[ch][gr][sb])
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minscaleindex[ch][sb] = scalar[ch][gr][sb];
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/* Oh yeah. Fudge the hell out of the SMR calculations by combining the scalefactor table index
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and the min ATH in that subband There are probably more elegant/correct ways of combining
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these values, but who cares? It works pretty well MFC Mar 03 */
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for (ch = 0; ch < nch; ch++)
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for (sb = 0; sb < SBLIMIT; sb++)
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SMR[ch][sb] = 2.0 * (30.0 - minscaleindex[ch][sb]) - mem->ath_min[sb];
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}
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void psycho_0_deinit(psycho_0_mem ** mem)
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{
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if (mem == NULL || *mem == NULL)
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return;
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TWOLAME_FREE(*mem);
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}
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// vim:ts=4:sw=4:nowrap:
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