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

Matthew Phillips mythtv at mattp.name
Mon Mar 28 02:41:17 UTC 2005

On 28/03/2005, at 9:15 AM, Michael Carland wrote:

> 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.

Hi Michael,

I had a very similar problem which cropped up after switching to ALSA 
output. After a long saga of list-trawling, it turned out to be an 
error with an uninitialised variable in Myth's ALSA audio module (I so 
wish C++ would regard this sort of thing as an error). After grabbing a 
patch from CVS and rebuilding, all is fixed.

The patch against 0.17 is attached. Since we have the same frontend hw, 
I could look into making the (RPM) binaries available if there's 
somewhere to drop them.


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