[mythtv-users] Re: SAA7134 (Flyvideo 3000) not always capturingaudio

Christian Hack christianh at pdd.edmi.com.au
Tue Jul 15 20:26:51 EDT 2003


> -----Original Message-----
> From: mythtv-users-bounces at snowman.net 
> [mailto:mythtv-users-bounces at snowman.net] On Behalf Of Rob Nielsen
> Sent: Tuesday, 15 July 2003 6:57 PM
> 
> CH wrote:
>  >Anyone else had similar problems? I don't think it's the 
> driver since 
>  >if I use aplay /dev/dsp1 (the device created by the SAA7134 
> driver) it
>  >always works. It only seems to happen with Myth capturing the audio.
> 
> Hi.  I've just setup a system with 2 Flyvideo 3000 cards 
> (sound through 
> PCI bus) and am experiencing exactly the same thing.  It is 
> definately 
> on the recording side and looks like either a problem with 
> the driver or 
> the way MythTV tunes the channels as plugging speakers 
> directly into the 
> capture card produces no sound when it happens.
> 

Well at least it is reproducable. I haven't tried plugging speakers
directly into the tuner card when there is no audio, but I will tonight.
If as you report, no sound is coming from the card, then it basically
has to be a driver issue rather than a MythTV issue. Myth simply sets a
channel though V4L interface as I understand and then records from
/dev/videox and /dev/dspx.

> Other things I've found is that after a reboot, both tuners almost 
> always have no sound initially and I need to go to Watch TV, 
> ESC, Watch 
> TV... a few times to get them going but then after that you get the 
> occasional recording with no sound.

I am seeing this exact behaviour too.

> I'm also getting the volume differences between recordings 
> but generally 
> they are very quiet and I have to turn the volume right up on the TV. 
> Anyone know of a way of boosting the sound before it is recorded?

My difference in volume is not nearly as extreme as this. Assuming the
louder version is 100% volume, the quieter volume I get is about 75%.
It's not a biggy for me, but a little annoying to have to keep adjusting
the volume each time it changes.

> 
> As a workaround for this, if the cause can't be found, how 
> hard would it 
> be to sample the sound for a small period of time after a 
> channel change 
> and if there is no sound detected, then try retuning?

I'd rather fix it in the driver if possible than go hacking myth code.

> 
> Cheers,
> Rob.
> 

I am back on the video4linux list and once I get a good description I
will see what Gerd thinks. I'm unable to find any technical doco on the
SAA7134 (registers etc) so he's possibly the only one who can help.

At least I have a secondary tester once I start playing with code... ;)

CH



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