[mythtv-users] ac3 passthrough problems
Scott
list-mythtv at bluecamel.eml.cc
Tue Sep 26 13:59:46 UTC 2006
On Sep 25, 2006, at 9:16 PM, Brian J. Murrell wrote:
> On Fri, 2006-22-09 at 01:53 -0400, Scott wrote:
>>
>> Audio output device:
>> ALSA:iec958:CARD=0,AES0=0x6,AES1=0x82,AES2=0x0,AES3=0x2
>> Passthrough output device: Default
>
> Hrm. I did
>
> Audio output device: ALSA:iec958
> Passthrough output device:
> ALSA:iec958:CARD=0,AES0=0x6,AES1=0x82,AES2=0x0,AES3=0x2
>
> and I get digital PCM just fine for non AC3/DTS sound (i,e. analog
> SDTV
> recordings) but nothing for a (say) 5.1 sound track. ~sigh~
When you get no sound for a 5.1 sound track, continue to use the
above settings but try running mythfrontend -v audio > audio.debug
and then playing your 5.1 sound track source. In the audio.debug file
look for the ALSA lines to see if MythTV had trouble with any ALSA
devices.
> All of this is of course after trying the much more simple and
> straightforward "ALSA:iec958" or "ALSA:spdif" in the Passthrough
> option.
> Frequently I get the "helicopter blades" sound characterized elsewhere
> in this thread.
I've come to the conclusion that "helicopter blades" is the result of
sound being routed correctly BUT the headers are missing as Mike
stated a while back. Using the hex codes above would "fix" this. No,
I'm not sure how accurate this statement is but it's my current
working theory.
> Any further ideas?
1) In MythTV locate a 5.1 source that fails to play correctly
2) Exit Myth Frontend
3) Using mplayer, run "mplayer -v -ao alsa -afm hwac3
source_file_from_mythtv.mpg" and verify the sound works as expected
At step 3, if the sound doesn't work as expected then most likely the
problem is ALSA is not configured correctly yet. An asoundrc file
might help out. If the sound does work correctly then look for the
alsa-init lines produced by mplayer verbose output. They should tell
you exactly which device mplayer is using to get you 5.1 sound. Copy
that information down and paste it ot the list. The info mplayer
outputs won't be usable in the MythTV device fields as is but it can
be a good hint of the direction to run in.
Of course, all this assumes you're doing the following hookup: sound
card -> spdif -> A/V receiver. :)
--
Scott
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