Added adpcm2lin and lin2adpcm.

Modules/audioop.c

@@ -130,6 +130,9 @@ int sample;
     }
 /* End of code taken from sox */
 
+/* ADPCM step variation table */
+static float newstep[5] = { 0.8, 0.9, 1.0, 1.75, 1.75 };
+
 #define CHARP(cp, i) ((signed char *)(cp+i))
 #define SHORTP(cp, i) ((short *)(cp+i))
 #define LONGP(cp, i) ((long *)(cp+i))
@@ -546,6 +549,136 @@ audioop_ulaw2lin(self, args)
     return rv;
 }
 
+static object *
+audioop_lin2adpcm(self, args)
+    object *self;
+    object *args;
+{
+    signed char *cp;
+    signed char *ncp;
+    int len, size, val, step, valprev, delta;
+    object *rv, *state, *str;
+    int i;
+
+    if ( !getargs(args, "(s#iO)",
+		  &cp, &len, &size, &state) )
+      return 0;
+    
+
+    if ( size != 1 && size != 2 && size != 4) {
+	err_setstr(AudioopError, "Size should be 1, 2 or 4");
+	return 0;
+    }
+    
+    str = newsizedstringobject(NULL, len/size);
+    if ( str == 0 )
+      return 0;
+    ncp = (signed char *)getstringvalue(str);
+
+    /* Decode state, should have (value, step) */
+    if ( state == None ) {
+	/* First time, it seems. Set defaults */
+	valprev = 0;
+	step = 4;	/* The '4' is magic. Dunno it's significance */
+    } else if ( !getargs(state, "(ii)", &valprev, &step) )
+      return 0;
+
+    for ( i=0; i < len; i += size ) {
+	if ( size == 1 )      val = ((int)*CHARP(cp, i)) << 8;
+	else if ( size == 2 ) val = (int)*SHORTP(cp, i);
+	else if ( size == 4 ) val = ((int)*LONGP(cp, i)) >> 16;
+
+	/* Step 1 - compute difference with previous value */
+	delta = (val - valprev)/step;
+
+	/* Step 2 - Clamp */
+	if ( delta < -4 )
+	  delta = -4;
+	else if ( delta > 3 )
+	  delta = 3;
+
+	/* Step 3 - Update previous value */
+	valprev += delta*step;
+
+	/* Step 4 - Clamp previous value to 16 bits */
+	if ( valprev > 32767 )
+	  valprev = 32767;
+	else if ( valprev < -32768 )
+	  valprev = -32768;
+
+	/* Step 5 - Update step value */
+	step = step * newstep[abs(delta)];
+	step++;		/* Don't understand this. */
+
+	/* Step 6 - Output value (as a whole byte, currently) */
+	*ncp++ = delta;
+    }
+    rv = mkvalue("(O(ii))", str, valprev, step);
+    DECREF(str);
+    return rv;
+}
+
+static object *
+audioop_adpcm2lin(self, args)
+    object *self;
+    object *args;
+{
+    signed char *cp;
+    signed char *ncp;
+    int len, size, val, valprev, step, delta;
+    object *rv, *str, *state;
+    int i;
+
+    if ( !getargs(args, "(s#iO)",
+		  &cp, &len, &size, &state) )
+      return 0;
+
+    if ( size != 1 && size != 2 && size != 4) {
+	err_setstr(AudioopError, "Size should be 1, 2 or 4");
+	return 0;
+    }
+    
+    /* Decode state, should have (value, step) */
+    if ( state == None ) {
+	/* First time, it seems. Set defaults */
+	valprev = 0;
+	step = 4;	/* The '4' is magic. Dunno it's significance */
+    } else if ( !getargs(state, "(ii)", &valprev, &step) )
+      return 0;
+    
+    str = newsizedstringobject(NULL, len*size);
+    if ( str == 0 )
+      return 0;
+    ncp = (signed char *)getstringvalue(str);
+    
+    for ( i=0; i < len*size; i += size ) {
+	/* Step 1 - get the delta value */
+	delta = *cp++;
+
+	/* Step 2 - update output value */
+	valprev = valprev + delta*step;
+
+	/* Step 3 - clamp output value */
+	if ( valprev > 32767 )
+	  valprev = 32767;
+	else if ( valprev < -32768 )
+	  valprev = -32768;
+
+	/* Step 4 - Update step value */
+	step = step * newstep[abs(delta)];
+	step++;
+
+	/* Step 5 - Output value */
+	if ( size == 1 )      *CHARP(ncp, i) = (signed char)(valprev >> 8);
+	else if ( size == 2 ) *SHORTP(ncp, i) = (short)(valprev);
+	else if ( size == 4 ) *LONGP(ncp, i) = (long)(valprev<<16);
+    }
+
+    rv = mkvalue("(O(ii))", str, valprev, step);
+    DECREF(str);
+    return rv;
+}
+
 static struct methodlist audioop_methods[] = {
     { "max", audioop_max },
     { "avg", audioop_avg },
@@ -555,6 +688,8 @@ static struct methodlist audioop_methods[] = {
     { "bias", audioop_bias },
     { "ulaw2lin", audioop_ulaw2lin },
     { "lin2ulaw", audioop_lin2ulaw },
+    { "adpcm2lin", audioop_adpcm2lin },
+    { "lin2adpcm", audioop_lin2adpcm },
     { "tomono", audioop_tomono },
     { "tostereo", audioop_tostereo },
     { "getsample", audioop_getsample },