[mythtv] Work Around for SAA7134 Intial Sound Problems

d.williams at paradise.net.nz d.williams at paradise.net.nz
Tue Aug 12 11:45:58 EDT 2003


When looking into some other sound issues i was having with my FlyVideo 3000 
card (SAA7134 based card), I think I've found the cause of the problem with 
Mythtv and no recording of sound untill you watch live tv a couple of times,
(which a few people have noticed)

Basically the driver's hardcoded to mute it's output on startup.

I enabled the audio_debug module param for the saa7134 V4l2 module, and noticed 
the following:

What xawtv appears to do on startup:
  mute the card
  unmute the card

What myth appears to do:
   Nothing, assumes that the sound is enabled.

I don't know what the BTTV driver does (as I don't have a card that needs it),
so don't know if BTTV is muted by default or not!

I would have thought it would be a good idea for Myth to make sure the card is 
in the state that it expects. (I would do it, but don't have the skills to do 

I haven't managed to trace through the recording process  (I'm not a C++ Coder) 
to see if Myth attempts to make sure the card is not muted.

To work around /fix the issue:

In saa7134-video.c, function saa7134_video_init
change the line:
dev->ctl_mute       = 1;
dev->ctl_mute       = 0;

(This is based off the snapshot on the 6th August - but does appear to be in).

Now when mythtv starts, I get audio with no messing about. 8-)
(say goodbye to the biggest problem I had with myth - next stop getting the 
remote working properly 8-) ).

I've posted this to both the user  + developer lists

Oh - and also - it appears the the current method of getting sound working, 
going into live tv a couple time doesn't work under CVS anymore (at least not 
for me !)


P.s  Thanks to all the guys/girls who are doing the coding for mythtv, VERY 
much appeciated.

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