mp3lib/layer1.c

   1 /*
   2  * Mpeg Layer-1 audio decoder
   3  * --------------------------
   4  * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
   5  * near unoptimzed ...
   6  *
   7  * may have a few bugs after last optimization ...
   8  *
   9  */
  10
  11 /*
  12  * Modified for use with MPlayer, for details see the changelog at
  13  * http://svn.mplayerhq.hu/mplayer/trunk/
  14  * $Id$
  15  *
  16  * The above-mentioned README file has the following to say about licensing:
  17  *
  18  *   COPYING: you may use this source under LGPL terms!
  19  */
  20
  21 //#include "mpg123.h"
  22
  23 static void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
  24 {
  25   unsigned int *ba=balloc;
  26   unsigned int *sca = (unsigned int *) scale_index;
  27
  28   if(fr->stereo == 2) {
  29     int i;
  30     int jsbound = fr->jsbound;
  31     for (i=0;i<jsbound;i++) {
  32       *ba++ = getbits(4);
  33       *ba++ = getbits(4);
  34     }
  35     for (i=jsbound;i<SBLIMIT;i++)
  36       *ba++ = getbits(4);
  37
  38     ba = balloc;
  39
  40     for (i=0;i<jsbound;i++) {
  41       if ((*ba++))
  42         *sca++ = getbits(6);
  43       if ((*ba++))
  44         *sca++ = getbits(6);
  45     }
  46     for (i=jsbound;i<SBLIMIT;i++)
  47       if ((*ba++)) {
  48         *sca++ =  getbits(6);
  49         *sca++ =  getbits(6);
  50       }
  51   }
  52   else {
  53     int i;
  54     for (i=0;i<SBLIMIT;i++)
  55       *ba++ = getbits(4);
  56     ba = balloc;
  57     for (i=0;i<SBLIMIT;i++)
  58       if ((*ba++))
  59         *sca++ = getbits(6);
  60   }
  61 }
  62
  63 static void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
  64         unsigned int scale_index[2][SBLIMIT],struct frame *fr)
  65 {
  66   int i,n;
  67   int smpb[2*SBLIMIT]; /* values: 0-65535 */
  68   int *sample;
  69   register unsigned int *ba;
  70   register unsigned int *sca = (unsigned int *) scale_index;
  71
  72   if(fr->stereo == 2) {
  73     int jsbound = fr->jsbound;
  74     register real *f0 = fraction[0];
  75     register real *f1 = fraction[1];
  76     ba = balloc;
  77     for (sample=smpb,i=0;i<jsbound;i++)  {
  78       if ((n = *ba++))
  79         *sample++ = getbits(n+1);
  80       if ((n = *ba++))
  81         *sample++ = getbits(n+1);
  82     }
  83     for (i=jsbound;i<SBLIMIT;i++)
  84       if ((n = *ba++))
  85         *sample++ = getbits(n+1);
  86
  87     ba = balloc;
  88     for (sample=smpb,i=0;i<jsbound;i++) {
  89       if((n=*ba++))
  90         *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
  91       else
  92         *f0++ = 0.0;
  93       if((n=*ba++))
  94         *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
  95       else
  96         *f1++ = 0.0;
  97     }
  98     for (i=jsbound;i<SBLIMIT;i++) {
  99       if ((n=*ba++)) {
 100         real samp = ( ((-1)<<n) + (*sample++) + 1);
 101         *f0++ = samp * muls[n+1][*sca++];
 102         *f1++ = samp * muls[n+1][*sca++];
 103       }
 104       else
 105         *f0++ = *f1++ = 0.0;
 106     }
 107     for(i=fr->down_sample_sblimit;i<32;i++)
 108       fraction[0][i] = fraction[1][i] = 0.0;
 109   }
 110   else {
 111     register real *f0 = fraction[0];
 112     ba = balloc;
 113     for (sample=smpb,i=0;i<SBLIMIT;i++)
 114       if ((n = *ba++))
 115         *sample++ = getbits(n+1);
 116     ba = balloc;
 117     for (sample=smpb,i=0;i<SBLIMIT;i++) {
 118       if((n=*ba++))
 119         *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
 120       else
 121         *f0++ = 0.0;
 122     }
 123     for(i=fr->down_sample_sblimit;i<32;i++)
 124       fraction[0][i] = 0.0;
 125   }
 126 }
 127
 128 static int do_layer1(struct frame *fr,int single)
 129 {
 130   int clip=0;
 131   int i,stereo = fr->stereo;
 132   unsigned int balloc[2*SBLIMIT];
 133   unsigned int scale_index[2][SBLIMIT];
 134   DECLARE_ALIGNED(16, real, fraction[2][SBLIMIT]);
 135 //  int single = fr->single;
 136
 137 //  printf("do_layer1(0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X )\n",
 138 //    wordpointer[0],wordpointer[1],wordpointer[2],wordpointer[3],wordpointer[4],wordpointer[5],wordpointer[6],wordpointer[7]);
 139
 140   fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
 141                          (fr->mode_ext<<2)+4 : 32;
 142
 143   if(stereo == 1 || single == 3)
 144     single = 0;
 145
 146   I_step_one(balloc,scale_index,fr);
 147
 148   for (i=0;i<SCALE_BLOCK;i++)
 149   {
 150     I_step_two(fraction,balloc,scale_index,fr);
 151
 152     if(single >= 0)
 153     {
 154       clip += (fr->synth_mono)( (real *) fraction[single],pcm_sample,&pcm_point);
 155     }
 156     else {
 157         int p1 = pcm_point;
 158         clip += (fr->synth)( (real *) fraction[0],0,pcm_sample,&p1);
 159         clip += (fr->synth)( (real *) fraction[1],1,pcm_sample,&pcm_point);
 160     }
 161
 162   }
 163
 164   return clip;
 165 }
 166
 167