[mythtv-users] Sound Issues with VIA 82xx

Paul Barker pbarker at ntlworld.com
Sun Dec 5 21:04:24 UTC 2004

A while back I posted saying that I was having issues with sound using a
front end with embedded VIA 82xx audio and an optical digi out.
Basically whenever I went into TV / Music etc I got no sound until I
muted the IEC switch in the mixer. Each time I exited and went back into
to TV or anything else the switch was turned back on and the problem
returned. (This is an FC1 box by the way).
I'd tried all sorts of things to get it going but eventually lived with
a work around script which checked the switch every 5 secs and turned it
off if it was on.
Well I finally sat down and dedicated some time to find out exactly what
the problem was.
It turns out that the IEC958 switch basically turns the optical digi out
on and off. Something turns this on (possibly at boot but certainly each
time I go into TV or Music or whatever) and my AV amp is set to auto
source select. Iit sees light on the optical in then it tries to use the
digital input. I'm assuming that the signal on the optical line is not
the correct format and hence no sound. If I manually switch over to the
analog on the amp then, hey presto, sound !
So ... either the optical out shouldn't be on all the time (ASLA driver
? / OSS ? / Myth ?) or I need to direct all my output to the optical out
but get ALSA to convert the rate etc into the correct mode.
A couple of questions: 
1) Is Myth turning on the optical ? (I'm not set to use it by default
but if I set it to use ALSA:plug:spdif I get sound in TV but Music won't
use it - error could not open sound device).
2) Can ALSA do the rate convert so I could ship all my output to the
optical and would this be a good solution ?
If 2 is possible some pointers to some good resources on asoundrc from
the point of view of an ALSA newbie would be good :) I'm not looking for
the answer on a plate (but if you have one plated up ... ;) ) and I'm a
Systems Engineer so can probably work it out with some decent reference
Thanks, as always for any and all help. If anyone's interested I'll post
a conclusion.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-users/attachments/20041205/7fdb34e6/attachment.html

More information about the mythtv-users mailing list