[mythtv-users] ALSA and real AC3 passthrough

Petr Stehlik pstehlik at sophics.cz
Thu Dec 29 08:21:30 EST 2005

Hi all,

yesterday I switched my myth box from analog to digital sound output
(Asus K8V SE motherboard with its onboard sound). I got it working
relatively quickly with "ALSA:digital" driver (also "ALSA:default"
worked) but couldn't get the "AC3 passthrough" working correctly - on
AC3 DVB-S channels I heard only a noise. At last I managed to get the
AC3 passthrough (DVB-S ASTRA HD AC3 5.1 sound) working by setting
"ALSA:spdif" in myth. But that broke analog sound (analog TV capture to
32000 Hz MP3). Some analog sounds sometime work for a while if they are
44.1 kHz and the receiver is in a good mood (but it probably plays it a
bit faster since 44.1 is replayed as 48 kHz).

So basically I can get everything but real DVB-S AC3 passthrough working
with "ALSA:digital" or I can get everything but analog sound with

I copied the .asoundrc from the Digital Sound Howto.
Xine works properly with MP3 and AC3 sound.

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.

I currently think that it's not easily possible and that myth should
allow me to enter a different sound device for the passthrough. But
since xine handles it somehow then it might be possible. Please advise. 


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