--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/decoders/mpglib/layer1.c	Thu Feb 21 19:46:09 2002 +0000
@@ -0,0 +1,147 @@
+/* 
+ * Mpeg Layer-1 audio decoder 
+ * --------------------------
+ * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
+ * near unoptimzed ...
+ *
+ * may have a few bugs after last optimization ... 
+ *
+ */
+
+#include "mpg123_sdlsound.h"
+
+void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
+{
+  unsigned int *ba=balloc;
+  unsigned int *sca = (unsigned int *) scale_index;
+
+  if(fr->stereo) {
+    int i;
+    int jsbound = fr->jsbound;
+    for (i=0;i<jsbound;i++) { 
+      *ba++ = getbits(4);
+      *ba++ = getbits(4);
+    }
+    for (i=jsbound;i<SBLIMIT;i++)
+      *ba++ = getbits(4);
+
+    ba = balloc;
+
+    for (i=0;i<jsbound;i++) {
+      if ((*ba++))
+        *sca++ = getbits(6);
+      if ((*ba++))
+        *sca++ = getbits(6);
+    }
+    for (i=jsbound;i<SBLIMIT;i++)
+      if ((*ba++)) {
+        *sca++ =  getbits(6);
+        *sca++ =  getbits(6);
+      }
+  }
+  else {
+    int i;
+    for (i=0;i<SBLIMIT;i++)
+      *ba++ = getbits(4);
+    ba = balloc;
+    for (i=0;i<SBLIMIT;i++)
+      if ((*ba++))
+        *sca++ = getbits(6);
+  }
+}
+
+void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
+	unsigned int scale_index[2][SBLIMIT],struct frame *fr)
+{
+  int i,n;
+  int smpb[2*SBLIMIT]; /* values: 0-65535 */
+  int *sample;
+  register unsigned int *ba;
+  register unsigned int *sca = (unsigned int *) scale_index;
+
+  if(fr->stereo) {
+    int jsbound = fr->jsbound;
+    register real *f0 = fraction[0];
+    register real *f1 = fraction[1];
+    ba = balloc;
+    for (sample=smpb,i=0;i<jsbound;i++)  {
+      if ((n = *ba++))
+        *sample++ = getbits(n+1);
+      if ((n = *ba++))
+        *sample++ = getbits(n+1);
+    }
+    for (i=jsbound;i<SBLIMIT;i++) 
+      if ((n = *ba++))
+        *sample++ = getbits(n+1);
+
+    ba = balloc;
+    for (sample=smpb,i=0;i<jsbound;i++) {
+      if((n=*ba++))
+        *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
+      else
+        *f0++ = 0.0;
+      if((n=*ba++))
+        *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
+      else
+        *f1++ = 0.0;
+    }
+    for (i=jsbound;i<SBLIMIT;i++) {
+      if ((n=*ba++)) {
+        real samp = ( ((-1)<<n) + (*sample++) + 1);
+        *f0++ = samp * muls[n+1][*sca++];
+        *f1++ = samp * muls[n+1][*sca++];
+      }
+      else
+        *f0++ = *f1++ = 0.0;
+    }
+  }
+  else {
+    register real *f0 = fraction[0];
+    ba = balloc;
+    for (sample=smpb,i=0;i<SBLIMIT;i++)
+      if ((n = *ba++))
+        *sample++ = getbits(n+1);
+    ba = balloc;
+    for (sample=smpb,i=0;i<SBLIMIT;i++) {
+      if((n=*ba++))
+        *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
+      else
+        *f0++ = 0.0;
+    }
+  }
+}
+
+int do_layer1(struct frame *fr,unsigned char *pcm_sample,int *pcm_point)
+{
+  int clip=0;
+  int i,stereo = fr->stereo;
+  unsigned int balloc[2*SBLIMIT];
+  unsigned int scale_index[2][SBLIMIT];
+  real fraction[2][SBLIMIT];
+  int single = fr->single;
+
+  fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;
+
+  if(stereo == 1 || single == 3)
+    single = 0;
+
+  I_step_one(balloc,scale_index,fr);
+
+  for (i=0;i<SCALE_BLOCK;i++)
+  {
+    I_step_two(fraction,balloc,scale_index,fr);
+
+      if(single >= 0) {
+        clip += synth_1to1_mono( (real*)fraction[single],pcm_sample,pcm_point);
+      }
+      else {
+        int p1 = *pcm_point;
+        clip += synth_1to1( (real*)fraction[0],0,pcm_sample,&p1);
+        clip += synth_1to1( (real*)fraction[1],1,pcm_sample,pcm_point);
+      }
+  }
+
+  return clip;
+}
+
+