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