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158 lines
3.7 KiB
158 lines
3.7 KiB
/*
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* Mpeg Layer-1 audio decoder
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* --------------------------
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* copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
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* near unoptimzed ...
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*
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* may have a few bugs after last optimization ...
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*
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*/
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#include "mpg123.h"
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#include "getbits.h"
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void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
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{
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unsigned int *ba=balloc;
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unsigned int *sca = (unsigned int *) scale_index;
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if(fr->stereo) {
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int i;
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int jsbound = fr->jsbound;
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for (i=0;i<jsbound;i++) {
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*ba++ = getbits(&bsi,4);
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*ba++ = getbits(&bsi,4);
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}
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for (i=jsbound;i<SBLIMIT;i++)
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*ba++ = getbits(&bsi,4);
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ba = balloc;
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for (i=0;i<jsbound;i++) {
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if ((*ba++))
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*sca++ = getbits(&bsi,6);
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if ((*ba++))
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*sca++ = getbits(&bsi,6);
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}
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for (i=jsbound;i<SBLIMIT;i++)
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if ((*ba++)) {
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*sca++ = getbits(&bsi,6);
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*sca++ = getbits(&bsi,6);
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}
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}
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else {
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int i;
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for (i=0;i<SBLIMIT;i++)
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*ba++ = getbits(&bsi,4);
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ba = balloc;
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for (i=0;i<SBLIMIT;i++)
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if ((*ba++))
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*sca++ = getbits(&bsi,6);
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}
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}
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void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
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unsigned int scale_index[2][SBLIMIT],struct frame *fr)
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{
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int i,n;
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int smpb[2*SBLIMIT]; /* values: 0-65535 */
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int *sample;
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unsigned int *ba;
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unsigned int *sca = (unsigned int *) scale_index;
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if(fr->stereo) {
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int jsbound = fr->jsbound;
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real *f0 = fraction[0];
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real *f1 = fraction[1];
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ba = balloc;
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for (sample=smpb,i=0;i<jsbound;i++) {
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if ((n = *ba++))
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*sample++ = getbits(&bsi,n+1);
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if ((n = *ba++))
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*sample++ = getbits(&bsi,n+1);
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}
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for (i=jsbound;i<SBLIMIT;i++)
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if ((n = *ba++))
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*sample++ = getbits(&bsi,n+1);
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ba = balloc;
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for (sample=smpb,i=0;i<jsbound;i++) {
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if((n=*ba++))
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*f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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else
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*f0++ = 0.0;
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if((n=*ba++))
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*f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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else
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*f1++ = 0.0;
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}
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for (i=jsbound;i<SBLIMIT;i++) {
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if ((n=*ba++)) {
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real samp = ( ((-1)<<n) + (*sample++) + 1);
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*f0++ = samp * muls[n+1][*sca++];
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*f1++ = samp * muls[n+1][*sca++];
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}
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else
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*f0++ = *f1++ = 0.0;
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}
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for(i=fr->down_sample_sblimit;i<32;i++)
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fraction[0][i] = fraction[1][i] = 0.0;
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}
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else {
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real *f0 = fraction[0];
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ba = balloc;
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for (sample=smpb,i=0;i<SBLIMIT;i++)
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if ((n = *ba++))
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*sample++ = getbits(&bsi,n+1);
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ba = balloc;
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for (sample=smpb,i=0;i<SBLIMIT;i++) {
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if((n=*ba++))
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*f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
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else
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*f0++ = 0.0;
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}
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for(i=fr->down_sample_sblimit;i<32;i++)
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fraction[0][i] = 0.0;
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}
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}
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int do_layer1(struct mpstr *mp,struct frame *fr,int outmode,struct audio_info_struct *ai)
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{
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int clip=0;
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int i,stereo = fr->stereo;
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unsigned int balloc[2*SBLIMIT];
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unsigned int scale_index[2][SBLIMIT];
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real fraction[2][SBLIMIT];
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int single = fr->single;
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fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;
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if(stereo == 1 || single == 3)
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single = 0;
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I_step_one(balloc,scale_index,fr);
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for (i=0;i<SCALE_BLOCK;i++)
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{
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I_step_two(fraction,balloc,scale_index,fr);
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if(single >= 0)
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{
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clip += (fr->synth_mono)( (real *) fraction[single],pcm_sample,&pcm_point);
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}
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else {
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int p1 = pcm_point;
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clip += (fr->synth)( (real *) fraction[0],0,pcm_sample,&p1);
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clip += (fr->synth)( (real *) fraction[1],1,pcm_sample,&pcm_point);
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}
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if(pcm_point >= audiobufsize)
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audio_flush(outmode,ai);
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}
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return clip;
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}
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