Fix SDL audio playback with surround sound

If user has surround sound enabled, ioq3 would not play any sound.
Fix painting sound buffer for 4/5.1 audio channels. Extra channels
currently play no audio.

code/client/snd_dma.c

@@ -1339,7 +1339,7 @@ void S_Update_(void) {
 		& ~(dma.submission_chunk-1);
 
 	// never mix more than the complete buffer
-	samps = dma.samples >> (dma.channels-1);
+	samps = dma.samples / dma.channels;
 	if (endtime - s_soundtime > samps)
 		endtime = s_soundtime + samps;
 

code/client/snd_mix.c

@@ -150,18 +150,16 @@ void S_TransferPaintBuffer(int endtime)
 {
 	int 	out_idx;
 	int 	count;
-	int 	out_mask;
 	int 	*p;
 	int 	step;
 	int		val;
+	int		i;
 	unsigned long *pbuf;
 
 	pbuf = (unsigned long *)dma.buffer;
 
 
 	if ( s_testsound->integer ) {
-		int		i;
-
 		// write a fixed sine wave
 		count = (endtime - s_paintedtime);
 		for (i=0 ; i<count ; i++)
@@ -177,53 +175,73 @@ void S_TransferPaintBuffer(int endtime)
 	{	// general case
 		p = (int *) paintbuffer;
 		count = (endtime - s_paintedtime) * dma.channels;
-		out_mask = dma.samples - 1; 
-		out_idx = s_paintedtime * dma.channels & out_mask;
-		step = 3 - dma.channels;
+		out_idx = s_paintedtime * dma.channels % dma.samples;
+		step = 3 - MIN( dma.channels, 2 );
 
 		if ((dma.isfloat) && (dma.samplebits == 32))
 		{
 			float *out = (float *) pbuf;
-			while (count--)
+			for (i=0 ; i<count ; i++)
 			{
-				val = *p >> 8;
-				p+= step;
+				if ( i % dma.channels >= 2 )
+				{
+					val = 0;
+				}
+				else
+				{
+					val = *p >> 8;
+					p+= step;
+				}
 				if (val > 0x7fff)
 					val = 0x7fff;
 				else if (val < -32767)  /* clamp to one less than max to make division max out at -1.0f. */
 					val = -32767;
 				out[out_idx] = ((float) val) / 32767.0f;
-				out_idx = (out_idx + 1) & out_mask;
+				out_idx = (out_idx + 1) % dma.samples;
 			}
 		}
 		else if (dma.samplebits == 16)
 		{
 			short *out = (short *) pbuf;
-			while (count--)
+			for (i=0 ; i<count ; i++)
 			{
-				val = *p >> 8;
-				p+= step;
+				if ( i % dma.channels >= 2 )
+				{
+					val = 0;
+				}
+				else
+				{
+					val = *p >> 8;
+					p+= step;
+				}
 				if (val > 0x7fff)
 					val = 0x7fff;
 				else if (val < -32768)
 					val = -32768;
 				out[out_idx] = val;
-				out_idx = (out_idx + 1) & out_mask;
+				out_idx = (out_idx + 1) % dma.samples;
 			}
 		}
 		else if (dma.samplebits == 8)
 		{
 			unsigned char *out = (unsigned char *) pbuf;
-			while (count--)
+			for (i=0 ; i<count ; i++)
 			{
-				val = *p >> 8;
-				p+= step;
+				if ( i % dma.channels >= 2 )
+				{
+					val = 0;
+				}
+				else
+				{
+					val = *p >> 8;
+					p+= step;
+				}
 				if (val > 0x7fff)
 					val = 0x7fff;
 				else if (val < -32768)
 					val = -32768;
 				out[out_idx] = (val>>8) + 128;
-				out_idx = (out_idx + 1) & out_mask;
+				out_idx = (out_idx + 1) % dma.samples;
 			}
 		}
 	}

code/sdl/sdl_snd.c

@@ -267,14 +267,8 @@ qboolean SNDDMA_Init(void)
 	if (!tmp)
 		tmp = (obtained.samples * obtained.channels) * 10;
 
-	if (tmp & (tmp - 1))  // not a power of two? Seems to confuse something.
-	{
-		int val = 1;
-		while (val < tmp)
-			val <<= 1;
-
-		tmp = val;
-	}
+	// samples must be divisible by number of channels
+	tmp -= tmp % obtained.channels;
 
 	dmapos = 0;
 	dma.samplebits = SDL_AUDIO_BITSIZE(obtained.format);