[linux-dvb] No audio with MythTV

Anssi Hannula anssi.hannula at gmail.com
Sat Jul 7 00:35:09 CEST 2007

Howard Lowndes wrote:
> My setup is 3 machines all running Fedora Core 6 with 2.6.18 kernels.
> Machine 1 is my laptop where I want to run mythfrontend.
> Machine 2 is where I want to run mythbackend.
> Machine 3 is where I am running MySQL.
> I have compiled MythTV on m/c 1 and m/c 2 from source.
> I have no problems with running this setup as far as video is concerned 
> for DVB-T (I haven't yet tried composite or s-video) - everything works 
> fine.  My problem comes with getting any audio at all.
> I suspect that my problem might be with the capture card.  It's a 
> LifeView FlyDVB-T Duo PCI and does both analogue TV and digital TV 
> capture as well as composite and s-video capture.  The chip on the card 
> is a Phillips saa7134.  The card has two connectors up in one corner. 
> One is a 4 pin Molex type connector and is marked "CD IN" (I'm guessing 
> that the purpose of this is obvious).  Next to it is a 4 pin connector 
> that I think is an SB type connector and it is marked "AUDIO OUT".  The 
> card came without any card to motherboard cables and in the doco 
> (Windows only naturally) makes no reference to any cabling from card to 
> motherboard, but I suspect that such a cable is necessary.
> I do know that the sound systems work fine on both m/c 1 and m/c 2 under 
> other circumstances.
> So, my questions are:
> 1. Do I need to cable the sound separately, or should the sound be being 
> handled over the PCI bus along with the video stream?

The DVB stream that is transfered over PCI includes both video and 
audio, no need for cabling when DVB is in question.

> 2. What is the pin assignment for the SB connector?  I'm assuming at 
> this stage that it is the same as for the Molex, namely R G G L.

Don't know that one.

> 3. What do I need to do to either alsa or oss on the backend machine, 
> and also on the frontend machine?  I really am clueless as to how Linux 
> sound works.

Backend machine does not need audio, the DVB stream is transfered to the 
frontend machines.

> 4. How does MythTV capture and store the sound?  Does it do that as a 
> combined stream together with the video into the .nuv files?

I'm not familiar with MythTV, but I thought it recorded DVB into TS MPEG 
files. If it has the ability to record DVB to .nuv files as well, they 
contain audio as well.

> Any clues or pointers gratefully received - I'm getting good at lip 
> reading  :)

I'd guess MythTV frontend audio settings are not configured properly.

Anssi Hannula

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