[mythtv] Digital audio passthrough

[mythtv at meric.id.au]

> What's more puzzling is that audio stopped working for you sometime in
> August, when no change to either the audio code or the playback code
> was made.
> 
> I would start at looking at the root of the problem and your crap
> audio card which requires a full reboot of the PC whenever you play
> something else but 48kHz audio.
> 
> You can still set an alternate playback audio for digital, just like
> you could before

Ok, the 25578 reference may have been a little arbitrary.  5.1 Audio has
been unstable in some form or other since an update I performed in late
April (24270).  The previous update to that was 23367.  Initial issues
were occasional problems with slow audio - these could usually be fixed
by either seeking back or forward, or via switching inputs.  More recent
changes seem to have taken these issues from intermittent to always -
which is perhaps a good thing, as it should make it easier to find.

For reference, the sound driver issue doesn't require a reboot to fix,
simply a reload of the driver.  None of the hardware has changed in
years - the only changes have been in Myth itself.  This particular
configuration has worked with myth in the past (e.g. back in Jan), and
works now with other software (e.g. mplayer).

The alternate passthru audio device option isn't working for me anymore.
The most recent set of changes seems to have stopped this from working
at all.

Cheers,
Richard.