1 files changed, 99 insertions, 0 deletions
diff --git a/lib/envelope.c b/lib/envelope.c
new file mode 100644
index 00000000..428a371d
--- /dev/null
+++ b/lib/envelope.c
@@ -0,0 +1,99 @@
+/********************************************************************
+ *                                                                  *
+ * THIS FILE IS PART OF THE Ogg Vorbis SOFTWARE CODEC SOURCE CODE.  *
+ * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
+ * THE GNU PUBLIC LICENSE 2, WHICH IS INCLUDED WITH THIS SOURCE.    *
+ * PLEASE READ THESE TERMS DISTRIBUTING.                            *
+ *                                                                  *
+ * THE OggSQUISH SOURCE CODE IS (C) COPYRIGHT 1994-2000             *
+ * by Monty <monty@xiph.org> and The XIPHOPHORUS Company            *
+ * http://www.xiph.org/                                             *
+ *                                                                  *
+ ********************************************************************
+
+ function: PCM data envelope analysis and manipulation
+ last mod: $Id: envelope.c,v 1.15.4.1 2000/05/08 08:25:42 xiphmont Exp $
+
+ Preecho calculation.
+
+ ********************************************************************/
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <math.h>
+#include "vorbis/codec.h"
+
+#include "os.h"
+#include "mdct.h"
+#include "envelope.h"
+#include "bitwise.h"
+#include "window.h"
+
+void _ve_envelope_init(envelope_lookup *e,int samples_per){
+  int i;
+
+  e->winlen=samples_per;
+  e->window=malloc(e->winlen*sizeof(double));
+  mdct_init(&e->mdct,e->winlen);
+
+  /* We just use a straight sin(x) window for this */
+  for(i=0;i<e->winlen;i++)
+    e->window[i]=sin((i+.5)/e->winlen*M_PI);
+
+}
+
+void _ve_envelope_clear(envelope_lookup *e){
+  if(e->window)free(e->window);
+  mdct_clear(&e->mdct);
+  memset(e,0,sizeof(envelope_lookup));
+}
+
+/* use MDCT for spectral power estimation */
+
+static void _ve_deltas(double *deltas,double *pcm,int n,double *window,
+		       int winsize,mdct_lookup *m){
+  int i,j;
+  double *out=alloca(sizeof(double)*winsize);
+  
+  for(j=0;j<n;j++){
+    double acc=0.;
+ 
+    memcpy(out,pcm+j*winsize,winsize*sizeof(double));
+    for(i=0;i<winsize;i++)
+      out[i]*=window[i];
+
+    mdct_forward(m,out,out);
+
+    for(i=winsize/10;i<winsize/2;i++)
+      acc+=fabs(out[i]);
+    if(deltas[j]<acc)deltas[j]=acc;
+  }
+}
+
+void _ve_envelope_deltas(vorbis_dsp_state *v){
+  vorbis_info *vi=v->vi;
+  int step=vi->envelopesa;
+  
+  int dtotal=v->pcm_current/vi->envelopesa;
+  int dcurr=v->envelope_current;
+  int pch;
+  
+  if(dtotal>dcurr){
+    double *mult=v->multipliers+dcurr;
+    memset(mult,0,sizeof(double)*(dtotal-dcurr));
+      
+    for(pch=0;pch<vi->channels;pch++){
+      double *pcm=v->pcm[pch]+dcurr*step;
+      _ve_deltas(mult,pcm,dtotal-dcurr,v->ve.window,v->ve.winlen,&v->ve.mdct);
+    }
+    v->envelope_current=dtotal;
+
+  }
+}
+
+
+
+
+
+