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

[Matthew Phillips]

On 28/03/2005, at 11:22 PM, Michael Carland wrote:

> --- Matthew Phillips <mythtv at mattp.name> wrote:
>> 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.
>>
>> 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.
>>
>> Matthew.
>
> Thanks for the patch.
>
> At first, I thought it worked. When I started live tv, 4 pauses and one
> underrun where logged, but then it was looking good. That lasted about 
> a
> minute, and then it was back to the stuttering.
>
> It's a little confusing, it does not happen recording a program, and it
> does not happen when playing a recording, so it's not easy to pin on 
> the
> frontend or backend.

That's very odd. My impression is that live TV mode is really the same 
as watching a recording as it's laid down (with the added feature of 
the buffer being limited and circular). So the fact that you get the 
problem only with live TV is unexpected - I was getting it regardless 
of mode. I also found that FF/RW a few times would re-sync until the 
next time I hit pause/unpause or a signal glitch threw it off.

> May I ask what kind of tuner card you are using?

I'm using a VisionPlus VisionDTV DVB-T PCI card.

Matthew.