simplify and optimize SoundMixBuffer

stepmania/src/RageSoundManager.cpp

@@ -276,7 +276,7 @@ SoundMixBuffer::~SoundMixBuffer()
 
 void SoundMixBuffer::SetVolume( float f )
 {
-	vol = f;
+	vol = int(256*f);
 }
 
 void SoundMixBuffer::write(const Sint16 *buf, unsigned size)
@@ -295,28 +295,17 @@ void SoundMixBuffer::write(const Sint16 *buf, unsigned size)
 
 	for(unsigned pos = 0; pos < size; ++pos)
 	{
-		Sint32 samp = buf[pos] * 32768;
+		/* Scale volume and add. */
-
+		mixbuf[pos] += buf[pos] * vol;
-		/* Scale volume: */
-		samp = Sint32(samp * vol);
-
-		/* Add and clip.  Can't use clamp() here--we're clamping to
-		* the min and max of Sint32. */
-		if(samp > 0 && mixbuf[pos] + samp < mixbuf[pos])
-			mixbuf[pos] = INT_MAX;
-		else if(samp < 0 && mixbuf[pos] + samp > mixbuf[pos])
-			mixbuf[pos] = INT_MIN;
-		else
-			mixbuf[pos] = mixbuf[pos] + samp;
 	}
 }
 
 void SoundMixBuffer::read(Sint16 *buf)
 {
+	int clip=0;
 	for(unsigned pos = 0; pos < used; ++pos)
 	{
-		/* XXX: dither */
+		Sint32 out = (mixbuf[pos]) / 256;
-		Sint32 out = (mixbuf[pos]) / 32768;
 		out = clamp(out, -32768, 32767);
 		buf[pos] = Sint16(out);
 	}

stepmania/src/RageSoundManager.h

@@ -70,7 +70,7 @@ class SoundMixBuffer
 	Sint32 *mixbuf;
 	unsigned bufsize; /* actual allocated samples */
 	unsigned used; /* used samples */
-	float vol;
+	int vol; /* vol * 256 */
 
 public:
 	void write(const Sint16 *buf, unsigned size);