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/* MPEG/WAVE Sound library
(C) 1997 by Jung woo-jae */
// Mpeglayer1.cc
// It's for MPEG Layer 1
#include "mpegsound.h"
#include "synthesis.h"
// Tables for layer 1
static const REAL factortable[15] =
{
0.0,
(1.0/2.0) * (4.0/3.0), (1.0/4.0) * (8.0/7.0),
(1.0/8.0) * (16.0/15.0), (1.0/16.0) * (32.0/31.0),
(1.0/32.0) * (64.0/63.0), (1.0/64.0) * (128.0/127.0),
(1.0/128.0) * (256.0/255.0), (1.0/256.0) * (512.0/511.0),
(1.0/512.0) * (1024.0/1023.0), (1.0/1024.0) * (2048.0/2047.0),
(1.0/2048.0) * (4096.0/4095.0), (1.0/4096.0) * (8192.0/8191.0),
(1.0/8192.0) * (16384.0/16383.0), (1.0/16384.0) * (32768.0/32767.0)
};
static const REAL offsettable[15] =
{
0.0,
((1.0/2.0)-1.0) * (4.0/3.0), ((1.0/4.0)-1.0) * (8.0/7.0),
((1.0/8.0)-1.0) * (16.0/15.0), ((1.0/16.0)-1.0) * (32.0/31.0),
((1.0/32.0)-1.0) * (64.0/63.0), ((1.0/64.0)-1.0) * (128.0/127.0),
((1.0/128.0)-1.0) * (256.0/255.0), ((1.0/256.0)-1.0) * (512.0/511.0),
((1.0/512.0)-1.0) * (1024.0/1023.0), ((1.0/1024.0)-1.0) * (2048.0/2047.0),
((1.0/2048.0)-1.0) * (4096.0/4095.0), ((1.0/4096.0)-1.0) * (8192.0/8191.0),
((1.0/8192.0)-1.0) * (16384.0/16383.0), ((1.0/16384.0)-1.0) * (32768.0/32767.0)
};
// Mpeg layer 1
void Mpegtoraw::extractlayer1(void)
{
int inputstereo=mpegAudioHeader->getInputstereo();
int stereobound=mpegAudioHeader->getStereobound();
REAL fraction[MAXCHANNEL][MAXSUBBAND];
REAL scalefactor[MAXCHANNEL][MAXSUBBAND];
int bitalloc[MAXCHANNEL][MAXSUBBAND],
sample[MAXCHANNEL][MAXSUBBAND];
int i,j;
int s=stereobound,l;
// Bitalloc
for(i=0;i<s;i++)
{
bitalloc[LS][i]=getbits(4);
bitalloc[RS][i]=getbits(4);
}
for(;i<MAXSUBBAND;i++)
bitalloc[LS][i]=
bitalloc[RS][i]=getbits(4);
// Scale index
if(inputstereo)
for(i=0;i<MAXSUBBAND;i++)
{
if(bitalloc[LS][i])scalefactor[LS][i]=scalefactorstable[getbits(6)];
if(bitalloc[RS][i])scalefactor[RS][i]=scalefactorstable[getbits(6)];
}
else
for(i=0;i<MAXSUBBAND;i++)
if(bitalloc[LS][i])scalefactor[LS][i]=scalefactorstable[getbits(6)];
for(l=0;l<SCALEBLOCK;l++)
{
// Sample
for(i=0;i<s;i++)
{
if((j=bitalloc[LS][i]))sample[LS][i]=getbits(j+1);
if((j=bitalloc[RS][i]))sample[RS][i]=getbits(j+1);
}
for(;i<MAXSUBBAND;i++)
if((j=bitalloc[LS][i]))sample[LS][i]=sample[RS][i]=getbits(j+1);
// Fraction
if(lOutputStereo)
for(i=0;i<MAXSUBBAND;i++)
{
if((j=bitalloc[LS][i]))
fraction[LS][i]=(REAL(sample[LS][i])*factortable[j]+offsettable[j])
*scalefactor[LS][i];
else fraction[LS][i]=0.0;
if((j=bitalloc[RS][i]))
fraction[RS][i]=(REAL(sample[RS][i])*factortable[j]+offsettable[j])
*scalefactor[RS][i];
else fraction[RS][i]=0.0;
}
else
for(i=0;i<MAXSUBBAND;i++)
if((j=bitalloc[LS][i]))
fraction[LS][i]=(REAL(sample[LS][i])*factortable[j]+offsettable[j])
*scalefactor[LS][i];
else fraction[LS][i]=0.0;
synthesis->doSynth(lDownSample,lOutputStereo,
fraction[LS],fraction[RS]);
}
}
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