--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/decoders/mpglib/layer2.c	Thu Feb 21 19:46:09 2002 +0000
@@ -0,0 +1,288 @@
+/* 
+ * Mpeg Layer-2 audio decoder 
+ * --------------------------
+ * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
+ *
+ */
+
+#include "mpg123_sdlsound.h"
+#include "l2tables.h"
+
+static int grp_3tab[32 * 3] = { 0, };   /* used: 27 */
+static int grp_5tab[128 * 3] = { 0, };  /* used: 125 */
+static int grp_9tab[1024 * 3] = { 0, }; /* used: 729 */
+
+real muls[27][64];	/* also used by layer 1 */
+
+void init_layer2(void)
+{
+  static double mulmul[27] = {
+    0.0 , -2.0/3.0 , 2.0/3.0 ,
+    2.0/7.0 , 2.0/15.0 , 2.0/31.0, 2.0/63.0 , 2.0/127.0 , 2.0/255.0 ,
+    2.0/511.0 , 2.0/1023.0 , 2.0/2047.0 , 2.0/4095.0 , 2.0/8191.0 ,
+    2.0/16383.0 , 2.0/32767.0 , 2.0/65535.0 ,
+    -4.0/5.0 , -2.0/5.0 , 2.0/5.0, 4.0/5.0 ,
+    -8.0/9.0 , -4.0/9.0 , -2.0/9.0 , 2.0/9.0 , 4.0/9.0 , 8.0/9.0 };
+  static int base[3][9] = {
+     { 1 , 0, 2 , } ,
+     { 17, 18, 0 , 19, 20 , } ,
+     { 21, 1, 22, 23, 0, 24, 25, 2, 26 } };
+  int i,j,k,l,len;
+  real *table;
+  static int tablen[3] = { 3 , 5 , 9 };
+  static int *itable,*tables[3] = { grp_3tab , grp_5tab , grp_9tab };
+
+  for(i=0;i<3;i++)
+  {
+    itable = tables[i];
+    len = tablen[i];
+    for(j=0;j<len;j++)
+      for(k=0;k<len;k++)
+        for(l=0;l<len;l++)
+        {
+          *itable++ = base[i][l];
+          *itable++ = base[i][k];
+          *itable++ = base[i][j];
+        }
+  }
+
+  for(k=0;k<27;k++)
+  {
+    double m=mulmul[k];
+    table = muls[k];
+    for(j=3,i=0;i<63;i++,j--)
+      *table++ = m * pow(2.0,(double) j / 3.0);
+    *table++ = 0.0;
+  }
+}
+
+
+void II_step_one(unsigned int *bit_alloc,int *scale,struct frame *fr)
+{
+    int stereo = fr->stereo-1;
+    int sblimit = fr->II_sblimit;
+    int jsbound = fr->jsbound;
+    int sblimit2 = fr->II_sblimit<<stereo;
+    struct al_table *alloc1 = fr->alloc;
+    int i;
+    static unsigned int scfsi_buf[64];
+    unsigned int *scfsi,*bita;
+    int sc,step;
+
+    bita = bit_alloc;
+    if(stereo)
+    {
+      for (i=jsbound;i;i--,alloc1+=(1<<step))
+      {
+        *bita++ = (char) getbits(step=alloc1->bits);
+        *bita++ = (char) getbits(step);
+      }
+      for (i=sblimit-jsbound;i;i--,alloc1+=(1<<step))
+      {
+        bita[0] = (char) getbits(step=alloc1->bits);
+        bita[1] = bita[0];
+        bita+=2;
+      }
+      bita = bit_alloc;
+      scfsi=scfsi_buf;
+      for (i=sblimit2;i;i--)
+        if (*bita++)
+          *scfsi++ = (char) getbits_fast(2);
+    }
+    else /* mono */
+    {
+      for (i=sblimit;i;i--,alloc1+=(1<<step))
+        *bita++ = (char) getbits(step=alloc1->bits);
+      bita = bit_alloc;
+      scfsi=scfsi_buf;
+      for (i=sblimit;i;i--)
+        if (*bita++)
+          *scfsi++ = (char) getbits_fast(2);
+    }
+
+    bita = bit_alloc;
+    scfsi=scfsi_buf;
+    for (i=sblimit2;i;i--) 
+      if (*bita++)
+        switch (*scfsi++) 
+        {
+          case 0: 
+                *scale++ = getbits_fast(6);
+                *scale++ = getbits_fast(6);
+                *scale++ = getbits_fast(6);
+                break;
+          case 1 : 
+                *scale++ = sc = getbits_fast(6);
+                *scale++ = sc;
+                *scale++ = getbits_fast(6);
+                break;
+          case 2: 
+                *scale++ = sc = getbits_fast(6);
+                *scale++ = sc;
+                *scale++ = sc;
+                break;
+          default:              /* case 3 */
+                *scale++ = getbits_fast(6);
+                *scale++ = sc = getbits_fast(6);
+                *scale++ = sc;
+                break;
+        }
+
+}
+
+void II_step_two(unsigned int *bit_alloc,real fraction[2][4][SBLIMIT],int *scale,struct frame *fr,int x1)
+{
+    int i,j,k,ba;
+    int stereo = fr->stereo;
+    int sblimit = fr->II_sblimit;
+    int jsbound = fr->jsbound;
+    struct al_table *alloc2,*alloc1 = fr->alloc;
+    unsigned int *bita=bit_alloc;
+    int d1,step;
+
+    for (i=0;i<jsbound;i++,alloc1+=(1<<step))
+    {
+      step = alloc1->bits;
+      for (j=0;j<stereo;j++)
+      {
+        if ( (ba=*bita++) ) 
+        {
+          k=(alloc2 = alloc1+ba)->bits;
+          if( (d1=alloc2->d) < 0) 
+          {
+            real cm=muls[k][scale[x1]];
+            fraction[j][0][i] = ((real) ((int)getbits(k) + d1)) * cm;
+            fraction[j][1][i] = ((real) ((int)getbits(k) + d1)) * cm;
+            fraction[j][2][i] = ((real) ((int)getbits(k) + d1)) * cm;
+          }        
+          else 
+          {
+            static int *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
+            unsigned int idx,*tab,m=scale[x1];
+            idx = (unsigned int) getbits(k);
+            tab = (unsigned int *) (table[d1] + idx + idx + idx);
+            fraction[j][0][i] = muls[*tab++][m];
+            fraction[j][1][i] = muls[*tab++][m];
+            fraction[j][2][i] = muls[*tab][m];  
+          }
+          scale+=3;
+        }
+        else
+          fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = 0.0;
+      }
+    }
+
+    for (i=jsbound;i<sblimit;i++,alloc1+=(1<<step))
+    {
+      step = alloc1->bits;
+      bita++;	/* channel 1 and channel 2 bitalloc are the same */
+      if ( (ba=*bita++) )
+      {
+        k=(alloc2 = alloc1+ba)->bits;
+        if( (d1=alloc2->d) < 0)
+        {
+          real cm;
+          cm=muls[k][scale[x1+3]];
+          fraction[1][0][i] = (fraction[0][0][i] = (real) ((int)getbits(k) + d1) ) * cm;
+          fraction[1][1][i] = (fraction[0][1][i] = (real) ((int)getbits(k) + d1) ) * cm;
+          fraction[1][2][i] = (fraction[0][2][i] = (real) ((int)getbits(k) + d1) ) * cm;
+          cm=muls[k][scale[x1]];
+          fraction[0][0][i] *= cm; fraction[0][1][i] *= cm; fraction[0][2][i] *= cm;
+        }
+        else
+        {
+          static int *table[] = { 0,0,0,grp_3tab,0,grp_5tab,0,0,0,grp_9tab };
+          unsigned int idx,*tab,m1,m2;
+          m1 = scale[x1]; m2 = scale[x1+3];
+          idx = (unsigned int) getbits(k);
+          tab = (unsigned int *) (table[d1] + idx + idx + idx);
+          fraction[0][0][i] = muls[*tab][m1]; fraction[1][0][i] = muls[*tab++][m2];
+          fraction[0][1][i] = muls[*tab][m1]; fraction[1][1][i] = muls[*tab++][m2];
+          fraction[0][2][i] = muls[*tab][m1]; fraction[1][2][i] = muls[*tab][m2];
+        }
+        scale+=6;
+      }
+      else {
+        fraction[0][0][i] = fraction[0][1][i] = fraction[0][2][i] =
+        fraction[1][0][i] = fraction[1][1][i] = fraction[1][2][i] = 0.0;
+      }
+/* 
+   should we use individual scalefac for channel 2 or
+   is the current way the right one , where we just copy channel 1 to
+   channel 2 ?? 
+   The current 'strange' thing is, that we throw away the scalefac
+   values for the second channel ...!!
+-> changed .. now we use the scalefac values of channel one !! 
+*/
+    }
+
+    for(i=sblimit;i<SBLIMIT;i++)
+      for (j=0;j<stereo;j++)
+        fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = 0.0;
+
+}
+
+static void II_select_table(struct frame *fr)
+{
+  static int translate[3][2][16] =
+   { { { 0,2,2,2,2,2,2,0,0,0,1,1,1,1,1,0 } ,
+       { 0,2,2,0,0,0,1,1,1,1,1,1,1,1,1,0 } } ,
+     { { 0,2,2,2,2,2,2,0,0,0,0,0,0,0,0,0 } ,
+       { 0,2,2,0,0,0,0,0,0,0,0,0,0,0,0,0 } } ,
+     { { 0,3,3,3,3,3,3,0,0,0,1,1,1,1,1,0 } ,
+       { 0,3,3,0,0,0,1,1,1,1,1,1,1,1,1,0 } } };
+
+  int table,sblim;
+  static struct al_table *tables[5] =
+       { alloc_0, alloc_1, alloc_2, alloc_3 , alloc_4 };
+  static int sblims[5] = { 27 , 30 , 8, 12 , 30 };
+
+  if(fr->lsf)
+    table = 4;
+  else
+    table = translate[fr->sampling_frequency][2-fr->stereo][fr->bitrate_index];
+  sblim = sblims[table];
+
+  fr->alloc      = tables[table];
+  fr->II_sblimit = sblim;
+}
+
+int do_layer2(struct frame *fr,unsigned char *pcm_sample,int *pcm_point)
+{
+  int clip=0;
+  int i,j;
+  int stereo = fr->stereo;
+  real fraction[2][4][SBLIMIT]; /* pick_table clears unused subbands */
+  unsigned int bit_alloc[64];
+  int scale[192];
+  int single = fr->single;
+
+  II_select_table(fr);
+  fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
+     (fr->mode_ext<<2)+4 : fr->II_sblimit;
+
+  if(stereo == 1 || single == 3)
+    single = 0;
+
+  II_step_one(bit_alloc, scale, fr);
+
+  for (i=0;i<SCALE_BLOCK;i++) 
+  {
+    II_step_two(bit_alloc,fraction,scale,fr,i>>2);
+    for (j=0;j<3;j++) {
+      if(single >= 0) {
+        clip += synth_1to1_mono(fraction[0][j],pcm_sample,pcm_point);
+      }
+      else {
+        int p1 = *pcm_point;
+        clip += synth_1to1(fraction[0][j],0,pcm_sample,&p1);
+        clip += synth_1to1(fraction[1][j],1,pcm_sample,pcm_point);
+      }
+
+    }
+  }
+
+  return clip;
+}
+
+