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2 pj 1
/*
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 * Mpeg Layer-2 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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 *
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 */
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#include "mpg123.h"
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static int grp_3tab[32 * 3] = { 0, };   /* used: 27 */
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static int grp_5tab[128 * 3] = { 0, };  /* used: 125 */
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static int grp_9tab[1024 * 3] = { 0, }; /* used: 729 */
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14
real muls[27][64];      /* also used by layer 1 */
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16
void init_layer2(void)
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{
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  static double mulmul[27] = {
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    0.0 , -2.0/3.0 , 2.0/3.0 ,
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    2.0/7.0 , 2.0/15.0 , 2.0/31.0, 2.0/63.0 , 2.0/127.0 , 2.0/255.0 ,
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    2.0/511.0 , 2.0/1023.0 , 2.0/2047.0 , 2.0/4095.0 , 2.0/8191.0 ,
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    2.0/16383.0 , 2.0/32767.0 , 2.0/65535.0 ,
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    -4.0/5.0 , -2.0/5.0 , 2.0/5.0, 4.0/5.0 ,
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    -8.0/9.0 , -4.0/9.0 , -2.0/9.0 , 2.0/9.0 , 4.0/9.0 , 8.0/9.0 };
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  static int base[3][9] = {
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     { 1 , 0, 2 , } ,
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     { 17, 18, 0 , 19, 20 , } ,
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     { 21, 1, 22, 23, 0, 24, 25, 2, 26 } };
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  int i,j,k,l,len;
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  real *table;
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  static int tablen[3] = { 3 , 5 , 9 };
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  static int *itable,*tables[3] = { grp_3tab , grp_5tab , grp_9tab };
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34
  for(i=0;i<3;i++)
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  {
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    itable = tables[i];
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    len = tablen[i];
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    for(j=0;j<len;j++)
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      for(k=0;k<len;k++)
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        for(l=0;l<len;l++)
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        {
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          *itable++ = base[i][l];
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          *itable++ = base[i][k];
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          *itable++ = base[i][j];
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        }
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  }
47
 
48
  for(k=0;k<27;k++)
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  {
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    double m=mulmul[k];
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    table = muls[k];
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    for(j=3,i=0;i<63;i++,j--)
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      *table++ = m * pow(2.0,(double) j / 3.0);
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    *table++ = 0.0;
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  }
56
}
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58
 
59
void II_step_one(unsigned int *bit_alloc,int *scale,struct frame *fr)
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{
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    int stereo = fr->stereo-1;
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    int sblimit = fr->II_sblimit;
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    int jsbound = fr->jsbound;
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    int sblimit2 = fr->II_sblimit<<stereo;
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    struct al_table *alloc1 = fr->alloc;
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    int i;
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    static unsigned int scfsi_buf[64];
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    unsigned int *scfsi,*bita;
69
    int sc,step;
70
 
71
    bita = bit_alloc;
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    if(stereo)
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    {
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      for (i=jsbound;i;i--,alloc1+=(1<<step))
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      {
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        *bita++ = (char) getbits(step=alloc1->bits);
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        *bita++ = (char) getbits(step);
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      }
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      for (i=sblimit-jsbound;i;i--,alloc1+=(1<<step))
80
      {
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        bita[0] = (char) getbits(step=alloc1->bits);
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        bita[1] = bita[0];
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        bita+=2;
84
      }
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      bita = bit_alloc;
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      scfsi=scfsi_buf;
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      for (i=sblimit2;i;i--)
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        if (*bita++)
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          *scfsi++ = (char) getbits_fast(2);
90
    }
91
    else /* mono */
92
    {
93
      for (i=sblimit;i;i--,alloc1+=(1<<step))
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        *bita++ = (char) getbits(step=alloc1->bits);
95
      bita = bit_alloc;
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      scfsi=scfsi_buf;
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      for (i=sblimit;i;i--)
98
        if (*bita++)
99
          *scfsi++ = (char) getbits_fast(2);
100
    }
101
 
102
    bita = bit_alloc;
103
    scfsi=scfsi_buf;
104
    for (i=sblimit2;i;i--)
105
      if (*bita++)
106
        switch (*scfsi++)
107
        {
108
          case 0:
109
                *scale++ = getbits_fast(6);
110
                *scale++ = getbits_fast(6);
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                *scale++ = getbits_fast(6);
112
                break;
113
          case 1 :
114
                *scale++ = sc = getbits_fast(6);
115
                *scale++ = sc;
116
                *scale++ = getbits_fast(6);
117
                break;
118
          case 2:
119
                *scale++ = sc = getbits_fast(6);
120
                *scale++ = sc;
121
                *scale++ = sc;
122
                break;
123
          default:              /* case 3 */
124
                *scale++ = getbits_fast(6);
125
                *scale++ = sc = getbits_fast(6);
126
                *scale++ = sc;
127
                break;
128
        }
129
 
130
}
131
 
132
void II_step_two(unsigned int *bit_alloc,real fraction[2][4][SBLIMIT],int *scale,struct frame *fr,int x1)
133
{
134
    int i,j,k,ba;
135
    int stereo = fr->stereo;
136
    int sblimit = fr->II_sblimit;
137
    int jsbound = fr->jsbound;
138
    struct al_table *alloc2,*alloc1 = fr->alloc;
139
    unsigned int *bita=bit_alloc;
140
    int d1,step;
141
 
142
    for (i=0;i<jsbound;i++,alloc1+=(1<<step))
143
    {
144
      step = alloc1->bits;
145
      for (j=0;j<stereo;j++)
146
      {
147
        if ( (ba=*bita++) )
148
        {
149
          k=(alloc2 = alloc1+ba)->bits;
150
          if( (d1=alloc2->d) < 0)
151
          {
152
            real cm=muls[k][scale[x1]];
153
            fraction[j][0][i] = ((real) ((int)getbits(k) + d1)) * cm;
154
            fraction[j][1][i] = ((real) ((int)getbits(k) + d1)) * cm;
155
            fraction[j][2][i] = ((real) ((int)getbits(k) + d1)) * cm;
156
          }        
157
          else
158
          {
159
            static int *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
160
            unsigned int idx,*tab,m=scale[x1];
161
            idx = (unsigned int) getbits(k);
162
            tab = (unsigned int *) (table[d1] + idx + idx + idx);
163
            fraction[j][0][i] = muls[*tab++][m];
164
            fraction[j][1][i] = muls[*tab++][m];
165
            fraction[j][2][i] = muls[*tab][m];  
166
          }
167
          scale+=3;
168
        }
169
        else
170
          fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = 0.0;
171
      }
172
    }
173
 
174
    for (i=jsbound;i<sblimit;i++,alloc1+=(1<<step))
175
    {
176
      step = alloc1->bits;
177
      bita++;   /* channel 1 and channel 2 bitalloc are the same */
178
      if ( (ba=*bita++) )
179
      {
180
        k=(alloc2 = alloc1+ba)->bits;
181
        if( (d1=alloc2->d) < 0)
182
        {
183
          real cm;
184
          cm=muls[k][scale[x1+3]];
185
          fraction[1][0][i] = (fraction[0][0][i] = (real) ((int)getbits(k) + d1) ) * cm;
186
          fraction[1][1][i] = (fraction[0][1][i] = (real) ((int)getbits(k) + d1) ) * cm;
187
          fraction[1][2][i] = (fraction[0][2][i] = (real) ((int)getbits(k) + d1) ) * cm;
188
          cm=muls[k][scale[x1]];
189
          fraction[0][0][i] *= cm; fraction[0][1][i] *= cm; fraction[0][2][i] *= cm;
190
        }
191
        else
192
        {
193
          static int *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
194
          unsigned int idx,*tab,m1,m2;
195
          m1 = scale[x1]; m2 = scale[x1+3];
196
          idx = (unsigned int) getbits(k);
197
          tab = (unsigned int *) (table[d1] + idx + idx + idx);
198
          fraction[0][0][i] = muls[*tab][m1]; fraction[1][0][i] = muls[*tab++][m2];
199
          fraction[0][1][i] = muls[*tab][m1]; fraction[1][1][i] = muls[*tab++][m2];
200
          fraction[0][2][i] = muls[*tab][m1]; fraction[1][2][i] = muls[*tab][m2];
201
        }
202
        scale+=6;
203
      }
204
      else {
205
        fraction[0][0][i] = fraction[0][1][i] = fraction[0][2][i] =
206
        fraction[1][0][i] = fraction[1][1][i] = fraction[1][2][i] = 0.0;
207
      }
208
/*
209
   should we use individual scalefac for channel 2 or
210
   is the current way the right one , where we just copy channel 1 to
211
   channel 2 ??
212
   The current 'strange' thing is, that we throw away the scalefac
213
   values for the second channel ...!!
214
-> changed .. now we use the scalefac values of channel one !!
215
*/
216
    }
217
 
218
    if(sblimit > (SBLIMIT>>fr->down_sample) )
219
      sblimit = SBLIMIT>>fr->down_sample;
220
 
221
    for(i=sblimit;i<SBLIMIT;i++)
222
      for (j=0;j<stereo;j++)
223
        fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = 0.0;
224
 
225
}
226
 
227
int do_layer2(struct frame *fr,int outmode,struct audio_info_struct *ai)
228
{
229
  int clip=0;
230
  int i,j;
231
  int stereo = fr->stereo;
232
  real fraction[2][4][SBLIMIT]; /* pick_table clears unused subbands */
233
  unsigned int bit_alloc[64];
234
  int scale[192];
235
  int single = fr->single;
236
 
237
  if(stereo == 1 || single == 3)
238
    single = 0;
239
 
240
  II_step_one(bit_alloc, scale, fr);
241
 
242
  for (i=0;i<SCALE_BLOCK;i++)
243
  {
244
    II_step_two(bit_alloc,fraction,scale,fr,i>>2);
245
    for (j=0;j<3;j++)
246
    {
247
      if(single >= 0)
248
      {
249
        clip += (fr->synth_mono) (fraction[single][j],pcm_sample+pcm_point);
250
      }
251
      else {
252
          clip += (fr->synth) (fraction[0][j],0,pcm_sample+pcm_point);
253
          clip += (fr->synth) (fraction[1][j],1,pcm_sample+pcm_point);
254
      }
255
      pcm_point += fr->block_size;
256
 
257
      if(pcm_point == audiobufsize)
258
        audio_flush(outmode,ai);
259
    }
260
  }
261
 
262
  return clip;
263
}
264
 
265