[mythtv-users] saa7134 audio problems

David Zanetti dave2 at wetstring.net
Sat Jan 17 18:31:09 EST 2004

Hash: SHA1

On Sat, 17 Jan 2004 hpoley at dds.nl wrote:

> I can't get sound to work in MythTV 0.12/0.13. I can hear the channel
> with xawtv and running 'aplay /dev/dsp1/' together. But MythTV doesn't
> seem to grab anything from it. No errors reported by either
> mythbackend nor mythfrontend (both with '-v all')

Various people in the past have suggested ensuring the card is unmuted
with `v4lctl volume 100%` and `v4lctl volume mute off`. For me, that
didn't work, and I had to actually change the logic with which Myth
decides to unmute audio.

It decides the input has audio if the VIDEO_VC_AUDIO flag is passed back
as a result of the VIDIOCGCHAN ioctl. The problem is the V4L1
compatiblity module doesn't set that ever, so Myth won't unmute it. The
current saa7134 driver is V4L2, so you're stuck with the compat module.

I looked at tvtime, and it decides it has audio by a different means, so I
changed my copy to that. I posted that suggestion to the -dev list, but
didn't get a response. 

In any case, hunt around libs/libmythtv/NuppleVideoRecorder.cpp, look for:

    // if channel has a audio then activate it
    if ((vchan.flags & VIDEO_VC_AUDIO) == VIDEO_VC_AUDIO) {

Change to:

    // if channel has a audio then activate it
    if (ioctl(fd, VIDIOCGAUDIO, &va) >= 0) {

Should work then. YMMV.

- -- 
David Zanetti           |  (__)             
#include <geek/unix.h>  |  ( oo    Mooooooo 
http://hairy.geek.nz/   |  /(_O ./         

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