[mythtv-users] Re: [mythtv] HDTV audio static

[Kyle Rose]

Forwarded to mythtv-users in case it helps more people.

Kyle Rose <krose+mythtv at krose.org> writes:

> John Patrick Poet <john at BlueSkyTours.com> writes:
>
>> The behavior you describe would happen if the audio stream is Dolby Digital,
>> you have AC3 passthrough turned on, but your receiver does not know how to
>> decode it.
>
> This is not it.  The static only happens about 50% of the time.  The
> other 50% is split between getting full, correct audio and getting
> only audio from the right channel.  Furthermore, I have AC3
> passthrough enabled on xine and the nuv files play just fine there.

So, it turns out that this *is* part of it, but there's more to the
problem: the emu10k1 ALSA drivers in 2.6 are broken with respect to
AC3 passthrough.

When I disable the kernel internal ALSA support and compile in the
1.0.5a-2 alsa-source from Debian unstable, I can then get passthrough
to work flawlessly if I set the audio device in Myth to ALSA:spdif and
turn on AC3 passthrough.  With the kernel drivers, I get pulsating
static with the same Myth settings.

Note that I use a Digital I/O 2 daughter card with my SB Live! 5.1,
and have the receiver hooked up to the coax SPD/IF out on the Digital
I/O dongle.

FWIW, what was really confusing me before is that AC3 passthrough
wasn't *really* on in xine, even though it looked like it was.  The
xine config settings are not very easy to grok.

Cheers,
Kyle