[mythtv-users] Audio query (fwd)

Nick knowledgejunkie at gmail.com
Mon Nov 14 14:25:04 EST 2005


On 13/11/05, Bob Purdon <bobp at aussie.nu> wrote:
>
> Hi guys,
>
> I've just installed the latest KnoppMyth installation on a machine here. All
> work well, except for the audio :-(
>
> Audio generally works on the machine - I can play MP3's, and AVI files play
> just fine.
>
> The problem is audio from the TV capture card.  I have free to air plugged into
> the TV input on the card, and pay-tv plugged into the S-Video input.
>
> Generally no issues with the pay-TV - I have to manually select the line-input
> on my sound card, but once I get things working I can use an external command
> to do that for me.  The audio from the pay-TV is connected to the line-in on
> the sound card (fed directly from the pay-TV decoder).
>
> The real issue is getting audio from the free-to-air - the TV card has an
> analogue audio out.  This is connected to the MIC in on the sound card.
> Additionally, it has an output on the card itself that I've connected to the
> AUX on the sound card (but either way, the result is the same).
>
> What I find is that in MythTV, I get video but no audio (and no amount of
> tweaking the mixer settings fixes it, mostly because I've confirmed there's
> actually no audio leaving the TV card).
>
> If I fire up xawtv, I get audio, but no video!  (although both were working in
> xawtv yesterday).
>
> If I fire up xawtv, then MythTV (at the same time), and then kill xawtv, I seem
> to get video and audio working OK.
>
> This is making me wonder if MythTV is failing to enable audio on the TV card.
>
> The TV card is a generic Askey CPH061 - nothing special.  I'll get a better
> card sometime soon, but for now this is the card I want to use.
>
> Has anyone come across this and successfully addressed it?

I seem to recall similar questions about this kind of problem -
checking the archives may be of help:

http://www.gossamer-threads.com/lists/mythtv/users/

Your card seems to be a BT878 card, so the following may help you out:

http://mythtv.info/moin.cgi/BtaudioHowTo

I suppose the big question is whether the external audio out on the TV
card outputs sound from all input sources or just routes non-tuner
input audio back out of the card.

To see what xawtv is doing (when it plays audio properly) fire up
alsamixer beforehand and take note of playback and recording settings.
Then fire up xawtv and see if it changes any of the settings. If you
can mute one of the inputs and xawtv stop making noise, you have
identified the input xawtv is using.

http://www.gossamer-threads.com/lists/mythtv/users/79416

I would also investigate whether the card supports btaudio (see above)
If it does, you should be able to

- disconnect all audio cables
- connect the pay-TV audio into the audio input on the TV card.

As the TV card audio is then taken care of via ALSA, you shouldn't
need extra cables.

Nick


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