[mythtv-users] ALSA Native audio splitting?

Cory Papenfuss papenfuss at juneau.me.vt.edu
Sat Oct 2 11:21:39 EDT 2004

 	I've got a question that I'm sure can be answered by someone who 
knows more about ALSA than I.  One of my motivations for doing The Big 
Mythtv Upgrade of late is to get to FC2 with 2.6 kernel, and get ALSA 
working.  I've seen a number of docs, but I haven't found one that 
addresses what I"m looking for.  I would like all audio (both mythtv/watch 
recordings, and mythvideo/mythdvd) to output audio to *both* SPDIF of my 
SBLIVE and the PCM output.  The way I see it, there are two things going 
on then:

Case #1: AC3 audio (e.g. watching DVD)
SPDIF:	use hwac3 and pipe directly to Dolby Digital receiver
PCM:	use a52 software AC3 decoder out regular line out

Case #2: No AC3 audio (e.g. watching TV, playing mp3's)
SPDIF:	Output PCM out SPDIF to DD receiver
PCM:	Play stream using normal MP2 decoding, etc

 	Ideally, everything would autodetect and output both all the time 
no matter what was playing.  Then if you were just watching TV you 
wouldn't have to fire up the receiver and could just use the TV audio. 
If you wanted to switch to more enveloping audio, switch on the receiver 
and mute the TV.  I would assume this could be set up with clever 
.asoundrc to pipe to two things at once.  Alsa is just so configurable I 
can't possibly figure out how to configure it... sorta like Emacs... :)

Thanks for any tips

* Cory Papenfuss							*
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University 			*

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