[mythtv-users] HELP! Selecting alternate audio o/p

Anthony Messina amessina at messinet.com
Mon Oct 2 06:47:22 UTC 2006

Robin Gilks wrote:
> Greetings
> After a power surge, it looks like my Epia SP13000 audio outputs are
> fried. The digital o/p is OK and I imagine that the mic and line-in are
> OK.
> Is there a way of routing the audio to either the digital o/p (for all
> sources, AC3 or just plain stereo) or is there a hidden control on the
> alsa mixer of a V8237 chip to turn the mic/line-in into outputs and use
> one of them as an analog output.


while this is not specific to your card, it may point you in the right

in your /etc/asound.conf or your $HOME/.asoundrc you should place:

## Start ##
defaults.pcm.card 0
defaults.pcm.device 1
defaults.ctl.card 0
# default ALSA route for software support of multiple sound streams
pcm.!default {
    type plug
    slave.pcm iec958dmix

# mix analog input to iec958 digital output
pcm.iec958dmix {
    type dmix
    ipc_key 1024
    slave {
        pcm "hw:0,1"
        format S32_LE

# iec958 optical digital output
pcm.!iec958 {
        type plug
        slave {
                pcm "hw:0,1"
                format S32_LE
## End ##

then tell mythtv in the general setup

audio output "ALSA:default"
passthrough "ALSA:iec958:{ AES0 0x6 AES1 0x82 AES2 0x0 AES3 0x2 }
then check the ac3 and dts passthrough boxes
then disable internal audio control

i suggest you play with your asound.conf (systemwide) or .asoundrc
(user-specific) files to get your digital sound working first, before
screwing with myth.  use xine or mplayer or something for that (as the
can play mpeg2 and passthrough digital sound.

in the above asound.conf file, you may substitute "spdif" instead of
"iec958" as necessary.  also, it's the dmix plugin that will route all
non-digital sound through your digital out.

visit alsa-project.org and alsa.opensrc.org for help. this page might be
of use: http://alsa.opensrc.org/via8233

good luck

Anthony -  http://messinet.com - http://messinet.com/~amessina/gallery
8F89 5E72 8DF0 BCF0 10BE 9967 92DC 35DC B001 4A4E

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