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2 pj 1
/*
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 * Mpeg Layer-1,2,3 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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 * version for slower machines .. decodes only every second sample
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 * sounds like 24000,22050 or 16000 kHz .. (depending on original sample freq.)
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 *
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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 "mpg123.h"
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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_2to1_8bit(real *bandPtr,int channel,unsigned char *samples)
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{
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  short samples_tmp[32];
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  short *tmp1 = samples_tmp + channel;
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  int i,ret;
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  samples += channel;
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  ret = synth_2to1(bandPtr,channel,(unsigned char *) samples_tmp);
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  for(i=0;i<16;i++) {
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    *samples = conv16to8[*tmp1>>4];
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    samples += 2;
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    tmp1 += 2;
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  }
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  return ret;
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}
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int synth_2to1_8bit_mono(real *bandPtr,unsigned char *samples)
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{
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  short samples_tmp[32];
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  short *tmp1 = samples_tmp;
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  int i,ret;
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  ret = synth_2to1(bandPtr,0,(unsigned char *) samples_tmp);
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  for(i=0;i<16;i++) {
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    *samples++ = conv16to8[*tmp1>>4];
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    *samples++ = conv16to8[*tmp1>>4];
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    tmp1 += 2;
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  }
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  return ret;
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}
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int synth_2to1_mono(real *bandPtr,unsigned char *samples)
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{
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  int i,ret = synth_2to1(bandPtr,0,samples);
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  for(i=0;i<16;i++) {
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    ((short *)samples)[1] = ((short *)samples)[0];
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    samples+=4;
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  }
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  return ret;
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}
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int synth_2to1(real *bandPtr,int channel,unsigned char *out)
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{
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  static real buffs[2][2][0x110];
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  static const int step = 2;
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  static int bo = 1;
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  short *samples = (short *) out;
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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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  if(!channel) {
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    bo--;
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    bo &= 0xf;
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    buf = buffs[0];
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  }
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  else {
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    samples++;
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    buf = 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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  {
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    register int j;
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    real *window = decwin + 16 - bo1;
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    for (j=8;j;j--,b0+=0x10,window+=0x30)
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    {
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      real sum;
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      sum  = *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      sum += *window++ * *b0++;
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      sum -= *window++ * *b0++;
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      WRITE_SAMPLE(samples,sum,clip); samples += step;
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#if 0
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      WRITE_SAMPLE(samples,sum,clip); samples += step;
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#endif
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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); samples += step;
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#if 0
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      WRITE_SAMPLE(samples,sum,clip); samples += step;
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#endif
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      b0-=0x20,window-=0x40;
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    }
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    window += bo1<<1;
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    for (j=7;j;j--,b0-=0x30,window-=0x30)
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    {
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      real sum;
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      sum = -*(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      sum -= *(--window) * *b0++;
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      WRITE_SAMPLE(samples,sum,clip); samples += step;
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#if 0
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      WRITE_SAMPLE(samples,sum,clip); samples += step;
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#endif
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    }
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  }
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  return clip;
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}
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