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