(some kind of) multichannel playback on emu10k cards

[Yuriy Tsibizov]

- does anyone need it?

I was playing with implementation of multichannel playback on emu10k based 
cards in emu10kx driver (availabale as emu10kx-snapshot from my website). 
As I know real multichannel playback is not supported by FreeBSD sound 
subsystem and I had to implement it as a number of stereo & mono PCM 
interfaces (each interface is connected to one of output connectors on 
card). From a dmesg it looks like this:

emu10kx0: <Creative Audigy [SB0090]> ....
emu10kx1: <Creative Audigy 2 [SB0240]> ....
emu10kx2: <Creative Audigy 2 Value [SB0400]> ....
pcm0: <EMU10Kx DSP FRONT PCM Interface> on emu10kx0
pcm0: <TriTech TR28602 AC97 Codec>
pcm1: <EMU10Kx DSP REAR PCM Interface> on emu10kx0
pcm2: <EMU10Kx DSP CENTER PCM Interface> on emu10kx0
pcm3: <EMU10Kx DSP SUBWOOFER PCM Interface> on emu10kx0
pcm4: <EMU10Kx DSP FRONT PCM Interface> on emu10kx1
pcm4: <SigmaTel STAC9721/23 AC97 Codec>
pcm5: <EMU10Kx DSP REAR PCM Interface> on emu10kx1
pcm6: <EMU10Kx DSP CENTER PCM Interface> on emu10kx1
pcm7: <EMU10Kx DSP SUBWOOFER PCM Interface> on emu10kx1
pcm8: <EMU10Kx DSP FRONT PCM Interface> on emu10kx2
pcm8: <SigmaTel STAC9750/51 AC97 Codec>
pcm9: <EMU10Kx DSP REAR PCM Interface> on emu10kx2
pcm10: <EMU10Kx DSP CENTER PCM Interface> on emu10kx2
pcm11: <EMU10Kx DSP SUBWOOFER PCM Interface> on emu10kx2
pcm12: <EMU10Kx DSP SIDE PCM Interface> on emu10kx2

First (FRONT) PCM interface has both playback and recording channels, it 
is also connected to an AC97 mixer, DSP inputs and AudigyDrive headphones. 
Other ones are for playback only.
On Audigy 2 there is also additional PCM interface to 'p16v' part of 
chipset (broken).

Current state:
DSP PCM playback: working, need some memory management cleanup
P16V PCM playback: broken
mixer: just a stub to let me adjust volume before playback and 
will need a rewrite
recording: does not work at all (because this part of mixer is broken)

It can be used with software multichannel sound decoder that can feed 
separate stereo & mono PCM streams into multiple dsp devices (i think 
mplayer can do it).

Yuriy Tsibizov,
http://chibis.persons.gfk.ru/audigy/