add support for up to 8 channels in sound effect files

The sounds are down-mixed to 2 channels (qf does not (yet) support more than
2 channel output), but this allows pretty much anything to be used for a
source of music. Only 5.1 (6 channel), stereo and mono have been tested, but
the others should work (any issues would be mis-interpretation/implementation
of the channel layout).

include/snd_render.h

@@ -50,6 +50,14 @@ typedef struct channel_s channel_t;
 typedef struct sfxbuffer_s sfxbuffer_t;
 typedef struct sfxblock_s sfxblock_t;
 typedef struct sfxstream_s sfxstream_t;
+/** paint samples into the mix buffer
+	\param offset   offset into the mix buffer at which to start mixing
+					the channel
+	\param ch		sound channel
+	\param buffer	sound data
+	\param count	number of frames to paint
+*/
+typedef void sfxpaint_t (int, channel_t *, float *, unsigned);
 
 /** Represent a sound sample in the mixer.
 */
@@ -99,15 +107,7 @@ struct sfxbuffer_s {
 	unsigned    length;			//!< length of buffer in frames
 	unsigned    pos;			//!< position of tail within full stream
 	unsigned    channels;		//!< number of channels per frame
-	/** paint samples into the mix buffer
+	sfxpaint_t *paint;			//!< channel count specific paint function
-		\param offset   offset into the mix buffer at which to start mixing
-						the channel
-		\param ch		sound channel
-		\param buffer	sound data
-		\param count	number of frames to paint
-	*/
-	void        (*paint) (int offset, channel_t *ch, float *buffer,
-						  unsigned count);
 	/** Advance the position with the stream, updating the ring buffer as
 		necessary. Null for chached sounds.
 		\param buffer	"this"

libs/audio/renderer/flac.c

@@ -453,7 +453,7 @@ SND_LoadFLAC (QFile *file, sfx_t *sfx, char *realname)
 		return -1;
 	}
 	info = flac_get_info (ff);
-	if (info.channels < 1 || info.channels > 2) {
+	if (info.channels < 1 || info.channels > 8) {
 		Sys_Printf ("unsupported number of channels");
 		return -1;
 	}

libs/audio/renderer/snd_mix.c

@@ -47,7 +47,7 @@ static __attribute__ ((used)) const char rcsid[] =
 #include "compat.h"
 #include "snd_render.h"
 
-#define VOLSCALE 1024.0				// so mixing is less likely to overflow
+#define VOLSCALE 512.0				// so mixing is less likely to overflow
 									// note: must be >= 255 due to the channel
 									// volumes being 0-255.
 
@@ -179,6 +179,45 @@ SND_PaintChannels (unsigned endtime)
 	}
 }
 
+static inline void
+snd_mix_single (portable_samplepair_t *pair, float **samp,
+				float lvol, float rvol)
+{
+	float       single = *(*samp)++;
+
+	pair->left += single * lvol;
+	pair->right += single * rvol;
+}
+
+static inline void
+snd_mix_pair (portable_samplepair_t *pair, float **samp,
+			  float lvol, float rvol)
+{
+	float       left = *(*samp)++;
+	float       right = *(*samp)++;
+
+	pair->left += left * lvol;
+	pair->right += right * rvol;
+}
+
+static inline void
+snd_mix_tripple (portable_samplepair_t *pair, float **samp,
+				 float lvol, float rvol)
+{
+	float       left = *(*samp)++;
+	float       center = *(*samp)++;
+	float       right = *(*samp)++;
+
+	pair->left += left * lvol;
+	pair->left += center * lvol;
+	pair->right += center * rvol;
+	pair->right += right * rvol;
+}
+
+/*	mono
+		center
+	Spacializes the sound.
+*/
 static void
 snd_paint_mono (int offs, channel_t *ch, float *sfx, unsigned count)
 {
@@ -273,6 +312,10 @@ snd_paint_mono (int offs, channel_t *ch, float *sfx, unsigned count)
 	}
 }
 
+/*	stereo
+		left, right
+	Does not spacialize the sound.
+*/
 static void
 snd_paint_stereo (int offs, channel_t *ch, float *samp, unsigned count)
 {
@@ -282,8 +325,135 @@ snd_paint_stereo (int offs, channel_t *ch, float *samp, unsigned count)
 
 	pair = snd_paintbuffer + offs;
 	while (count-- > 0) {
-		pair->left += *samp++ * leftvol;
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
-		pair->right += *samp++ * rightvol;
+		pair++;
+	}
+}
+
+/*	1d surround
+		left, center, right
+	Does not spacialize the sound.
+*/
+static void
+snd_paint_3 (int offs, channel_t *ch, float *samp, unsigned count)
+{
+	portable_samplepair_t *pair;
+	float       leftvol = ch->leftvol / VOLSCALE;
+	float       rightvol = ch->rightvol / VOLSCALE;
+
+	pair = snd_paintbuffer + offs;
+	while (count-- > 0) {
+		snd_mix_tripple (pair, &samp, leftvol, rightvol);
+		pair++;
+	}
+}
+
+/*	quadraphonic surround
+		front (left, right),
+		rear (left, right)
+	Does not spacialize the sound.
+*/
+static void
+snd_paint_4 (int offs, channel_t *ch, float *samp, unsigned count)
+{
+	portable_samplepair_t *pair;
+	float       leftvol = ch->leftvol / VOLSCALE;
+	float       rightvol = ch->rightvol / VOLSCALE;
+
+	pair = snd_paintbuffer + offs;
+	while (count-- > 0) {
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		pair++;
+	}
+}
+
+/*	five-channel surround
+		front (left, center, right),
+		rear (left, right)
+	Does not spacialize the sound.
+*/
+static void
+snd_paint_5 (int offs, channel_t *ch, float *samp, unsigned count)
+{
+	portable_samplepair_t *pair;
+	float       leftvol = ch->leftvol / VOLSCALE;
+	float       rightvol = ch->rightvol / VOLSCALE;
+
+	pair = snd_paintbuffer + offs;
+	while (count-- > 0) {
+		snd_mix_tripple (pair, &samp, leftvol, rightvol);
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		pair++;
+	}
+}
+
+/*	5.1 surround
+		front (left, center, right),
+		rear (left, right),
+		lfe
+	Does not spacialize the sound.
+*/
+static void
+snd_paint_6 (int offs, channel_t *ch, float *samp, unsigned count)
+{
+	portable_samplepair_t *pair;
+	float       leftvol = ch->leftvol / VOLSCALE;
+	float       rightvol = ch->rightvol / VOLSCALE;
+
+	pair = snd_paintbuffer + offs;
+	while (count-- > 0) {
+		snd_mix_tripple (pair, &samp, leftvol, rightvol);
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		snd_mix_single (pair, &samp, leftvol, rightvol);
+		pair++;
+	}
+}
+
+/*	6.1 surround
+		front (left, center, right),
+		side (left, right),
+		rear (center),
+		lfe
+	Does not spacialize the sound.
+*/
+static void
+snd_paint_7 (int offs, channel_t *ch, float *samp, unsigned count)
+{
+	portable_samplepair_t *pair;
+	float       leftvol = ch->leftvol / VOLSCALE;
+	float       rightvol = ch->rightvol / VOLSCALE;
+
+	pair = snd_paintbuffer + offs;
+	while (count-- > 0) {
+		snd_mix_tripple (pair, &samp, leftvol, rightvol);
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		snd_mix_single (pair, &samp, leftvol, rightvol);
+		snd_mix_single (pair, &samp, leftvol, rightvol);
+		pair++;
+	}
+}
+
+/*	7.1 surround
+		front (left, center, right),
+		side (left, right),
+		rear (left, right),
+		lfe
+	Does not spacialize the sound.
+*/
+static void
+snd_paint_8 (int offs, channel_t *ch, float *samp, unsigned count)
+{
+	portable_samplepair_t *pair;
+	float       leftvol = ch->leftvol / VOLSCALE;
+	float       rightvol = ch->rightvol / VOLSCALE;
+
+	pair = snd_paintbuffer + offs;
+	while (count-- > 0) {
+		snd_mix_tripple (pair, &samp, leftvol, rightvol);
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		snd_mix_pair (pair, &samp, leftvol, rightvol);
+		snd_mix_single (pair, &samp, leftvol, rightvol);
 		pair++;
 	}
 }
@@ -291,9 +461,20 @@ snd_paint_stereo (int offs, channel_t *ch, float *samp, unsigned count)
 void
 SND_SetPaint (sfxbuffer_t *sc)
 {
+	static sfxpaint_t *painters[] = {
+		0,
+		snd_paint_mono,
+		snd_paint_stereo,
+		snd_paint_3,
+		snd_paint_4,
+		snd_paint_5,
+		snd_paint_6,
+		snd_paint_7,
+		snd_paint_8,
+	};
+
 	wavinfo_t *info = sc->sfx->wavinfo (sc->sfx);
-	if (info->channels == 2)
+	if (info->channels < 0 || info->channels > 8)
-		sc->paint = snd_paint_stereo;
+		Sys_Error ("illegal channel count %d", info->channels);
-	else
+	sc->paint = painters[info->channels];
-		sc->paint = snd_paint_mono;
 }

libs/audio/renderer/vorbis.c

@@ -297,7 +297,7 @@ SND_LoadOgg (QFile *file, sfx_t *sfx, char *realname)
 		return -1;
 	}
 	info = vorbis_get_info (&vf);
-	if (info.channels < 1 || info.channels > 2) {
+	if (info.channels < 1 || info.channels > 8) {
 		Sys_Printf ("unsupported number of channels");
 		return -1;
 	}

libs/audio/renderer/wav.c

@@ -241,7 +241,7 @@ wav_get_info (QFile *file)
 		Sys_Printf ("not Microsfot PCM\n");
 		goto bail;
 	}
-	if (dfmt->channels < 1 || dfmt->channels > 2) {
+	if (dfmt->channels < 1 || dfmt->channels > 8) {
 		Sys_Printf ("unsupported channel count\n");
 		goto bail;
 	}