[mythtv-users] ALSA and SPDIF Out For nForce2 Motherboards
Michael T. Dean
mtdean at thirdcontact.com
Sun Apr 18 01:41:08 EDT 2004
> Did as advised: commented out the slave.pcm "digital" and removed the
> comment for slave.pcm "dmix-digital". I then made the change in
> MythTV from "ALSA:digital" to "ALSA:dmix-digital" for the "Audio
> output device". Rebooted the machine but still no joy. I'm able to
> get sound out via the analog output if I change "Audio output device"
> back to default of "/dev/dsp".
That's the problem. The section that I just had you change was the
section that defined a device called "default" (not called
"dmix-digital"). In other words, the default device is the device used
when no device is specified (i.e. a program uses the ALSA API but
doesn't request a specific device) or when the "default" device is
requested (i.e. for Myth, "ALSA:default").
I suppose I should have included a nice comment at the top of the
.asoundrc listing all the valid devices defined within. Anyway, the
only devices you should ever use are:
Note that if you leave the entire definition of "pcm.!default"
commented, default will be identical to analog. If you redefine default
by uncommenting the 4-line definition of "pcm.!default" default will be
identical to the device associated with the uncommented slave definition
(mixed-analog, digital, or mixed-digital from top to bottom as shown in
the .asoundrc I posted at
All other names in the .asoundrc--including "dmix-digital" are for
internal use only--they are virtual devices created as aliases to allow
reuse within the file.
So, try using "ALSA:digital" or "ALSA:mixed-digital" and see how it
works. (Or you could use "ALSA:default"--if you leave your .asoundrc as
is (based on the change you just made), this will be the same as using
BTW, that also means that there wasn't necessarily another program using
your audio device. Therefore, you can try both "ALSA:digital" and
"ALSA:mixed-digital" and use whichever you prefer. I recommend testing
by watching some TV and causing the computer to play other noises (i.e.
ssh to the computer and issue an aplay) to see how sound behaves. If
using "digital," the sounds will "queue up" (most likely causing the
application waiting for sound--here aplay--to block), but if using
"mixed-digital," the sounds will play (so the applications won't block).
Also, when you finish watching TV with unmixed output, you'll hear all
the sounds that got queued up--on my system, they play back much louder
than my videos, so it's quite scary to stop a playing video. Because of
that (and because the other sounds usually mean something), I'm using
mixed output (analog in my case because I'm hooked directly to the
More information about the mythtv-users