[mythtv] ALSA "fixes" actually break stuff in CVS?

Ed Wildgoose lists at wildgooses.com
Fri Dec 10 22:51:04 UTC 2004

>  First, without changing any of the previous settings, I went to watch 
> Live TV and I got a message saying that /dev/mixer wasn't a valid 
> device and couln't be accessed.  After a little research on the dev 
> mailing list archives I see that it said to put "default" as the mixer 
> device.  I also use software-dmix settings and an .asoundrc file so it 
> uses digital audio.

That's because in the past myth couldn't change volume unless you were 
using OSS.  Now it supports Alsa for volume and you asked it to use the 
volume device /dev/mixer (which I think you will agree is not an alsa 
control device).

>  Second, and this is the problem that basically makes Myth unusable, 
> is that after about 20-30 seconds of watching TV... I get WriteAudio: 
> buffer underrrun errors repeatidly until I exit to the main menu.  
> This causes the video and audio to go into a slow motion convulsion.  
> I have submitted a bug report because it had worked in all previous 
> versions of myth since .15 just fine.  I also reinstalled ALSA just in 
> case and update from 1.07RC2 to the latest release of 1.07 to verify 
> it wasn't something wrong with that.
>  Unfortuantly, there is (was) an overwhelming amount of reasons I used 
> CVS over .16 (functionality, features, and fixes).  I know that a lot 
> of work went into supposidly "fixing" ALSA in the current CVS, but I 
> don't really think it has fixed much besides breaking Myth.  I'm not 
> even sure how to troubleshoot or fix this problem at this point.  
> Anyone have any ideas?

It may well be a different issue.  Quite a lot has changed in the code 
since you last updated (besides audio).  Actually the alsa code is not 
so different from before, the main change I made was to simplify the 
duplicated code in all the output modules into one core place.  A couple 
of other people have then submitted changes which are logically correct 
to enhance the alsa output.

A lot of problems do stem from the drivers returning incorrect 
information to the myth code (which then does stupid things with the 
results).  Please try to post more useful debugging code if you really 
have a problem (knowing whether running it as root makes a difference 
would be interesting, as would knowing whether the OSS driver works better)

Good luck

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