Mercurial > sdl-ios-xcode
diff src/audio/alsa/SDL_alsa_audio.c @ 1878:d7c9d7f42881
Swizzle ALSA channels for 5.1 output to match DirectSound and CoreAudio.
Untested, but potentially fixes Bugzilla #110.
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Fri, 23 Jun 2006 08:35:48 +0000 |
| parents | 63fa37538842 |
| children | c121d94672cb a1b03ba2fcd0 |
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--- a/src/audio/alsa/SDL_alsa_audio.c Fri Jun 23 08:15:47 2006 +0000 +++ b/src/audio/alsa/SDL_alsa_audio.c Fri Jun 23 08:35:48 2006 +0000 @@ -264,14 +264,63 @@ } } + +/* + * 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 ) {