154 lines
3.5 KiB
C
154 lines
3.5 KiB
C
/*
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* Mpeg Layer-1,2,3 audio decoder
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* ------------------------------
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* copyright (c) 1995,1996,1997 by Michael Hipp, All rights reserved.
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* See also 'README'
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*
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* slighlty optimized for machines without autoincrement/decrement.
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* The performance is highly compiler dependend. Maybe
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* the decode.c version for 'normal' processor may be faster
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* even for Intel processors.
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*/
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#include <stdlib.h>
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#include <math.h>
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#include <string.h>
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#include "mpglib.h"
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/* old WRITE_SAMPLE */
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#define WRITE_SAMPLE(samples,sum,clip) \
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if( (sum) > 32767.0) { *(samples) = 0x7fff; (clip)++; } \
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else if( (sum) < -32768.0) { *(samples) = -0x8000; (clip)++; } \
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else { *(samples) = sum; }
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int synth_1to1_mono(struct mpstr *mp,real *bandPtr,unsigned char *samples,int *pnt)
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{
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short samples_tmp[64];
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short *tmp1 = samples_tmp;
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int i,ret;
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int pnt1 = 0;
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ret = synth_1to1(mp,bandPtr,0,(unsigned char *) samples_tmp,&pnt1);
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samples += *pnt;
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for(i=0;i<32;i++) {
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*( (short *) samples) = *tmp1;
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samples += 2;
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tmp1 += 2;
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}
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*pnt += 64;
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return ret;
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}
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int synth_1to1(struct mpstr *mp, real *bandPtr,int channel,unsigned char *out,int *pnt)
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{
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static const int step = 2;
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int bo;
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short *samples = (short *) (out + *pnt);
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real *b0,(*buf)[0x110];
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int clip = 0;
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int bo1;
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bo = mp->synth_bo;
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if(!channel) {
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bo--;
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bo &= 0xf;
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buf = mp->synth_buffs[0];
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}
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else {
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samples++;
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buf = mp->synth_buffs[1];
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}
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if(bo & 0x1) {
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b0 = buf[0];
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bo1 = bo;
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dct64(buf[1]+((bo+1)&0xf),buf[0]+bo,bandPtr);
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}
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else {
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b0 = buf[1];
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bo1 = bo+1;
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dct64(buf[0]+bo,buf[1]+bo+1,bandPtr);
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}
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mp->synth_bo = bo;
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{
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register int j;
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real *window = decwin + 16 - bo1;
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for (j=16;j;j--,b0+=0x10,window+=0x20,samples+=step)
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{
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real sum;
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sum = window[0x0] * b0[0x0];
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sum -= window[0x1] * b0[0x1];
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sum += window[0x2] * b0[0x2];
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sum -= window[0x3] * b0[0x3];
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sum += window[0x4] * b0[0x4];
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sum -= window[0x5] * b0[0x5];
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sum += window[0x6] * b0[0x6];
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sum -= window[0x7] * b0[0x7];
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sum += window[0x8] * b0[0x8];
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sum -= window[0x9] * b0[0x9];
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sum += window[0xA] * b0[0xA];
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sum -= window[0xB] * b0[0xB];
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sum += window[0xC] * b0[0xC];
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sum -= window[0xD] * b0[0xD];
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sum += window[0xE] * b0[0xE];
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sum -= window[0xF] * b0[0xF];
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WRITE_SAMPLE(samples,sum,clip);
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}
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{
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real sum;
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sum = window[0x0] * b0[0x0];
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sum += window[0x2] * b0[0x2];
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sum += window[0x4] * b0[0x4];
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sum += window[0x6] * b0[0x6];
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sum += window[0x8] * b0[0x8];
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sum += window[0xA] * b0[0xA];
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sum += window[0xC] * b0[0xC];
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sum += window[0xE] * b0[0xE];
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WRITE_SAMPLE(samples,sum,clip);
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b0-=0x10,window-=0x20,samples+=step;
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}
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window += bo1<<1;
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for (j=15;j;j--,b0-=0x10,window-=0x20,samples+=step)
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{
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real sum;
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sum = -window[-0x1] * b0[0x0];
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sum -= window[-0x2] * b0[0x1];
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sum -= window[-0x3] * b0[0x2];
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sum -= window[-0x4] * b0[0x3];
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sum -= window[-0x5] * b0[0x4];
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sum -= window[-0x6] * b0[0x5];
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sum -= window[-0x7] * b0[0x6];
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sum -= window[-0x8] * b0[0x7];
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sum -= window[-0x9] * b0[0x8];
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sum -= window[-0xA] * b0[0x9];
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sum -= window[-0xB] * b0[0xA];
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sum -= window[-0xC] * b0[0xB];
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sum -= window[-0xD] * b0[0xC];
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sum -= window[-0xE] * b0[0xD];
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sum -= window[-0xF] * b0[0xE];
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sum -= window[-0x0] * b0[0xF];
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WRITE_SAMPLE(samples,sum,clip);
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}
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}
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*pnt += 128;
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return clip;
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}
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