[mythtv-users] AC3 passthrough still doesn't work.
Kevin Kuphal
kuphal at dls.net
Sun Oct 24 16:03:23 UTC 2004
Bo Najdrovsky wrote:
> Well, I've made quite a bit of progress on my HD2000 based MythTV box,
> but there is one last remaining nagging issue, and that's the fact
> that the AC3 passthrough does not work in mythfrontend. I'm able to
> play the recorded .nuv files with mplayer, and the AC3 passthrough
> works fine with that program when I use the command line option -ao
> alsa:device=spdif This fact confirmed for me that my hardware is
> not at fault, but the bug must be in Myth. I went and recompiled
> MythTV 0.16 to make sure that ALSA output is enabled, restarted
> everything and put ALSA:spdif into the audio device field in front end
> configuration, but the results are the same as with OSS... I hear
> about quarter second of audio, and then silence. I'm guessing that
> perhaps mythfrontend isn't setting up the SPDIF port correctly. Any
> ideas?
>
AC3 passthrough does not mean that Myth will output on the SPDIF
connector. It means that if your content has AC3 audio then it will be
passed untouched to the audio device. If your recorded or live content
has anything but AC3 source material you will get only garbage. To get
output on the SPDIF connector, you need only configure ALSA OSS
emulation to output everything to it or, as you noted, use the
ALSA:spdif feature in the audio field.
Secondly, the ALSA support in Myth is somewhat in flux and also works
best with the 1.0.5a version of ALSA when compiled against it. The CVS
version has some fixes and also some patches are being worked on that
revamp the audio portion of Myth with better ALSA support. I don't know
if either of these will help but I wanted to make sure you were on the
right track and understood what the current status is.
Kevin
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