mp3lib/layer1.c

   1 /*
   2  * Modified for use with MPlayer, for details see the CVS changelog at
   3  * http://www.mplayerhq.hu/cgi-bin/cvsweb.cgi/main/
   4  * $Id$
   5  */
   6
   7 /*
   8  * Mpeg Layer-1 audio decoder
   9  * --------------------------
  10  * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
  11  * near unoptimzed ...
  12  *
  13  * may have a few bugs after last optimization ...
  14  *
  15  */
  16
  17 //#include "mpg123.h"
  18
  19 static void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
  20 {
  21   unsigned int *ba=balloc;
  22   unsigned int *sca = (unsigned int *) scale_index;
  23
  24   if(fr->stereo == 2) {
  25     int i;
  26     int jsbound = fr->jsbound;
  27     for (i=0;i<jsbound;i++) {
  28       *ba++ = getbits(4);
  29       *ba++ = getbits(4);
  30     }
  31     for (i=jsbound;i<SBLIMIT;i++)
  32       *ba++ = getbits(4);
  33
  34     ba = balloc;
  35
  36     for (i=0;i<jsbound;i++) {
  37       if ((*ba++))
  38         *sca++ = getbits(6);
  39       if ((*ba++))
  40         *sca++ = getbits(6);
  41     }
  42     for (i=jsbound;i<SBLIMIT;i++)
  43       if ((*ba++)) {
  44         *sca++ =  getbits(6);
  45         *sca++ =  getbits(6);
  46       }
  47   }
  48   else {
  49     int i;
  50     for (i=0;i<SBLIMIT;i++)
  51       *ba++ = getbits(4);
  52     ba = balloc;
  53     for (i=0;i<SBLIMIT;i++)
  54       if ((*ba++))
  55         *sca++ = getbits(6);
  56   }
  57 }
  58
  59 static void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
  60         unsigned int scale_index[2][SBLIMIT],struct frame *fr)
  61 {
  62   int i,n;
  63   int smpb[2*SBLIMIT]; /* values: 0-65535 */
  64   int *sample;
  65   register unsigned int *ba;
  66   register unsigned int *sca = (unsigned int *) scale_index;
  67
  68   if(fr->stereo == 2) {
  69     int jsbound = fr->jsbound;
  70     register real *f0 = fraction[0];
  71     register real *f1 = fraction[1];
  72     ba = balloc;
  73     for (sample=smpb,i=0;i<jsbound;i++)  {
  74       if ((n = *ba++))
  75         *sample++ = getbits(n+1);
  76       if ((n = *ba++))
  77         *sample++ = getbits(n+1);
  78     }
  79     for (i=jsbound;i<SBLIMIT;i++)
  80       if ((n = *ba++))
  81         *sample++ = getbits(n+1);
  82
  83     ba = balloc;
  84     for (sample=smpb,i=0;i<jsbound;i++) {
  85       if((n=*ba++))
  86         *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
  87       else
  88         *f0++ = 0.0;
  89       if((n=*ba++))
  90         *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
  91       else
  92         *f1++ = 0.0;
  93     }
  94     for (i=jsbound;i<SBLIMIT;i++) {
  95       if ((n=*ba++)) {
  96         real samp = ( ((-1)<<n) + (*sample++) + 1);
  97         *f0++ = samp * muls[n+1][*sca++];
  98         *f1++ = samp * muls[n+1][*sca++];
  99       }
 100       else
 101         *f0++ = *f1++ = 0.0;
 102     }
 103     for(i=fr->down_sample_sblimit;i<32;i++)
 104       fraction[0][i] = fraction[1][i] = 0.0;
 105   }
 106   else {
 107     register real *f0 = fraction[0];
 108     ba = balloc;
 109     for (sample=smpb,i=0;i<SBLIMIT;i++)
 110       if ((n = *ba++))
 111         *sample++ = getbits(n+1);
 112     ba = balloc;
 113     for (sample=smpb,i=0;i<SBLIMIT;i++) {
 114       if((n=*ba++))
 115         *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
 116       else
 117         *f0++ = 0.0;
 118     }
 119     for(i=fr->down_sample_sblimit;i<32;i++)
 120       fraction[0][i] = 0.0;
 121   }
 122 }
 123
 124 static int do_layer1(struct frame *fr,int single)
 125 {
 126   int clip=0;
 127   int i,stereo = fr->stereo;
 128   unsigned int balloc[2*SBLIMIT];
 129   unsigned int scale_index[2][SBLIMIT];
 130   real fraction[2][SBLIMIT];
 131 //  int single = fr->single;
 132
 133 //  printf("do_layer1(0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X )\n",
 134 //    wordpointer[0],wordpointer[1],wordpointer[2],wordpointer[3],wordpointer[4],wordpointer[5],wordpointer[6],wordpointer[7]);
 135
 136   fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
 137                          (fr->mode_ext<<2)+4 : 32;
 138
 139   if(stereo == 1 || single == 3)
 140     single = 0;
 141
 142   I_step_one(balloc,scale_index,fr);
 143
 144   for (i=0;i<SCALE_BLOCK;i++)
 145   {
 146     I_step_two(fraction,balloc,scale_index,fr);
 147
 148     if(single >= 0)
 149     {
 150       clip += (fr->synth_mono)( (real *) fraction[single],pcm_sample,&pcm_point);
 151     }
 152     else {
 153         int p1 = pcm_point;
 154         clip += (fr->synth)( (real *) fraction[0],0,pcm_sample,&p1);
 155         clip += (fr->synth)( (real *) fraction[1],1,pcm_sample,&pcm_point);
 156     }
 157
 158   }
 159
 160   return clip;
 161 }
 162
 163