Skip to content
Permalink
Browse files

Swizzle ALSA channels for 5.1 output to match DirectSound and CoreAudio.

 Untested, but potentially fixes Bugzilla #110.
  • Loading branch information
icculus committed Jun 23, 2006
1 parent 566543d commit 77799d92ac7a8742357699de1d30bdb29e9e2915

File 1 of 1 in 77799d9

@@ -264,14 +264,63 @@ static void ALSA_WaitAudio(_THIS)
}
}


/*
* http://bugzilla.libsdl.org/show_bug.cgi?id=110
* "For Linux ALSA, this is FL-FR-RL-RR-C-LFE
* and for Windows DirectX [and CoreAudio], this is FL-FR-C-LFE-RL-RR"
*/
#define SWIZ6(T) \
T *ptr = (T *) mixbuf; \
const Uint32 count = (this->spec.samples / 6); \
Uint32 i; \
for (i = 0; i < count; i++, ptr += 6) { \
T tmp; \
tmp = ptr[2]; ptr[2] = ptr[4]; ptr[4] = tmp; \
tmp = ptr[3]; ptr[3] = ptr[5]; ptr[5] = tmp; \
}

static __inline__ void swizzle_alsa_channels_6_64bit(_THIS) { SWIZ6(Uint64); }
static __inline__ void swizzle_alsa_channels_6_32bit(_THIS) { SWIZ6(Uint32); }
static __inline__ void swizzle_alsa_channels_6_16bit(_THIS) { SWIZ6(Uint16); }
static __inline__ void swizzle_alsa_channels_6_8bit(_THIS) { SWIZ6(Uint8); }

#undef SWIZ6


/*
* Called right before feeding this->mixbuf to the hardware. Swizzle channels
* from Windows/Mac order to the format alsalib will want.
*/
static __inline__ void swizzle_alsa_channels(_THIS)
{
if (this->spec.channels == 6) {
const Uint16 fmtsize = (this->spec.format & 0xFF); /* bits/channel. */
if (fmtsize == 16)
swizzle_alsa_channels_6_16bit(this);
else if (fmtsize == 8)
swizzle_alsa_channels_6_8bit(this);
else if (fmtsize == 32)
swizzle_alsa_channels_6_32bit(this);
else if (fmtsize == 64)
swizzle_alsa_channels_6_64bit(this);
}

/* !!! FIXME: update this for 7.1 if needed, later. */
}


static void ALSA_PlayAudio(_THIS)
{
int status;
int sample_len;
signed short *sample_buf;

swizzle_alsa_channels(this);

sample_len = this->spec.samples;
sample_buf = (signed short *)mixbuf;

while ( sample_len > 0 ) {
status = SDL_NAME(snd_pcm_writei)(pcm_handle, sample_buf, sample_len);
if ( status < 0 ) {

0 comments on commit 77799d9

Please sign in to comment.