[mythtv-users] ALSA and real AC3 passthrough

Petr Stehlik pstehlik at sophics.cz
Thu Dec 29 13:11:32 EST 2005

Lee Koloszyc píše v Čt 29. 12. 2005 v 09:12 -0500:

> > My question is whether it's possible to set up the .asoundrc in a way
> > that it handles both DVB-S AC3 real passthrough and also analog->digital
> > conversion plus 32kHz->48kHz resampling.

> In the .asoundrc I found on the web there is an Alsa section called dmix 

it's called dmix-digital in the Digital Sound HowTo.

> (digital mix) which will convert the analog sound to the proper format 
> for sending out through the spdif.

But does it allow for AC3 passthrough at the same time? Do you have some
AC3 sound source? Have you tried say HD DVB-S or perhaps DVD replayed
via the internal Myth DVD player (I guess that one would use the AC3
passthrough but I use xine so I don't know).

> pcm.nforce { type dmix ipc_key 1234 slave { pcm "hw:0,1" period_time 0 
> period_size 1024 buffer_size 4096 rate 44100 } }

I have a very similar section there.

> This may help, it is for gentoo, but you should get the general idea:
> http://gentoo-wiki.com/HOWTO_ALSA_sound_mixer_aka_dmix

They focus on getting the OSS emulation working. No word about AC3 and


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