[mythtv-users] SOLVED: Re: Exasperated: DD/DTS SPDIF works with everything *except* MythTV

[Kingsley Turner]

Kingsley Turner wrote:
> Allen Edwards wrote:
>>>>>> I have configured Myth to use
>>>>>>    "alsa:default" for audio,
>>>>>> and "ALSA:iec958:{AES0 0x02}" as the SPDIF output device.
>>>>>> Obviously the two checkboxes for sending AC3 and DTS sound out via SPDIF
>>>>>> are checked.
>>>>>>
>>>>>> Mplayer works fine with: -ao alsa:device=iec958 hwac3
>>>>>> VLC works fine with: --spdif    (oh, *so* easy!)
>>>>>>           
>>>>> Have you tried just "alsa:iec958" in Myth?
>>>>>         
>>>> Rename or delete asound.conf and .asoundrc.
>>>> Set the passthrough device to ALSA:iec958:{ AES0 0x02 }
>>>> Audio output device to ALSA:spdif.
>>>> If you are running Fedora, get rid of Pulse Audio (not
>>>> trivial apparently).
>>>> Turn on iec958 in alsamixer
>>>>       
>>> This is basically what I have already, except using ALSA:default instead
>>> of ALSA:spdif.
>>> I tried "ALSA:spdif", and got the same result.
>>>
>>> However I did notice that the digital sound (DD5.1 / playing DVD) seemed
>>> to be dropping in and out (according to the LED on the amp. anyway) and
>>> occasionally we'd get a split-second of sound before it dropped back to
>>> silence.  After changing back to ALSA:default I notice this is happening
>>> here also.  I'd guess it's not keeping up with the sound output or
>>> something, maybe some kind of buffering thing ??!  ("Agressive Sound
>>> card buffering" is turned OFF).
>>>     
>> Sorry, my reply was not complete:
>> Output ALSA:spdif
>> Passthrough device  ALSA:iec958:{ AES0 0x02 }
>> max Audio: Stereo (other setting is broken)
>> Upmix: Passive
>> Aggressive: unchecked
>> Internal Volume: I have it unchecked but I think it may work checked as well
>> Enable AC3 and DTS both checked.
>>
>> Hopefully you didn't have max audio set to stereo and this will fix
>> your problem
> I already had this set to stereo, but I read somewhere else it doesn't 
> effect digital out?
>
> Anyway, I just solved it this second:
>
> A quick little sentence in the MythTV wiki nailed it:
>
> http://www.mythtv.org/wiki/index.php/Configuring_Digital_Sound_with_AC3_and_SPDIF 
> -
>
> <quote>
> If "Use video as timebase" is checked, you will get stuttering audio 
> output or not audio at all. "Use video as timebase" *must* be 
> unchecked if you want AC3 audio to work.
> </quote>
>
> Just an offhand sentence, but *so* important!
>
> I don't know how I missed it, maybe because there's so many documents 
> on this, after you read a few of them you start to gloss-over them, 
> not reading properly.  Guess I was punished for my own lack of 
> thoroughness.
>
> Although, I wish the UI would give you a warning about this or 
> something.... ;)
>
> thanks to everyone for their help!
>

Interestingly I rebooted the box this morning after playing around with 
the lirc/imon stuff

I found that all audio in Myth stopped working (except playback of 
video, which is mplayer).  I changed the audio output device from 
ALSA:default to ALSA:spdif .   I don't know why it would suddenly become 
not working again, but the change fixed it.

cheers,
-kt

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