[mythtv-users] Re: Tips for fixing prebuffering pause and WriteAudio: buffer underrun

[SpikeyGG]

>From: Michael Carland <mcarland at yahoo.com>
>
>I seem to have all of my install mistakes corrected, except for one.
>
>When I play recorded content all is well. But when I play live TV, I get
>many  "prebuffering pause" messages, and an occasional "WriteAudio: buffer
>underrun". The video stutters during the prebuffering messages.
>
>I done some googling, and tried a few things, but have not been able to
>get around this. I am looking for tips on how to find the source of the
>problem.
>
>I have tried vmstat on both the frontend and the backend, and don't see
>anything that stands out. No swapping, plenty of memory, at least 20% idle
>cpu on both ends.
>
>I have the "Extra audio buffering" checked. I tried the "Aggresive
>Soundcard Buffering", but it didn't help, so I turned it back off.
>
>I am using ALSA on the frontend, and other than the stutters, it sounds
>fine.
>

I have a similar problem:

I've found that when I use ALSA without the "Extra audio buffering" it gives 
me lots of this:
2005-03-28 11:54:27.415 WriteAudio: buffer underrun
2005-03-28 11:54:28.202 WriteAudio: buffer underrun
2005-03-28 11:54:34.626 WriteAudio: buffer underrun
2005-03-28 11:54:34.924 WriteAudio: buffer underrun
2005-03-28 11:54:37.762 WriteAudio: buffer underrun
The audio on certian channels is crackly and the video is jumpy.  You can 
see from the timestamps that these babys fill up the logfile very quickly.

And if I enable the "Extra audio buffering" with ALSA it gives me lots of 
this:
2005-03-28 11:56:04.449 prebuffering pause
2005-03-28 11:56:06.250 prebuffering pause
2005-03-28 11:56:07.685 prebuffering pause
2005-03-28 11:56:08.621 prebuffering pause
2005-03-28 11:56:09.637 prebuffering pause
The audio skips ever so slightly and so does the video but it's better than 
the buffer undderrun.  The prebuffering pause messages come once a second... 
much slower than the underruns.

I haven't figured out how to fix either of these problems.  I'm running 
MythTV from CVS, with a pcHDTV HD-3000 card.  Most of the time I just use 
/dev/dsp but I've been wanting to use the ALSA because when I get a new 
reciever I'll be using the ALSA digital option to send it out the optical 
port.  Plus, I'd like to use a mixed audio driver so I never get caught with 
the "audio device is in use" message.  My hardware is nForce3 built-in sound 
on my motherboard.

Thanks,
-Greg