[mythtv-users] Playback problem -- random short pauses

[Dave Richardson]

 On Thu, 24 Mar 2011 10:03:28 -0500, Kenneth Emerson 
 <kenneth.emerson at gmail.com> wrote:
> I have been following several of the threads on this list (and the
> commit list) that have talked about "stuttering" during playback.  I
> don't believe that these issues are describing what I am seeing on my
> system.  My symptoms seem to have started happening about two months
> ago but I cannot pinpoint the time to some specific change in either
> my FE/BE combination or the version of mythTV.  I keep both my OS
> (Ubuntu 10.04 32 bit) and mythTV (24-fixes currently
> v0.24-227-gccd73be) up to date.  My version of NVIDIA driver is
> 260.19.21.  My system is based on an Intel Q6600 quad core 2.4GHz
> cpu.  The video being watched is primarily either 720p or 1080i
> material.  I don't believe I have ever seen the problem on 480
> material, but that data set may be too small to matter.
>
> The specific problem I see during playback is a random, short pause
> with either missing frames or missing audio; hard to tell which.  The
> pause is very short (less than 2 seconds) but long enough to miss 1-3
> words of the dialog.  The video is not damaged since I can back up
> and replay the same segment without any interruption.  These pauses
> are random and occur anywhere from none in an hour-long show to four
> or five times in that period.  It is not related to the scheduler
> starting/stopping other recordings as I check my watch every time one
> occurs.  I do see a slight stutter, occasionally, when I know there
> are other recordings stopping/starting and that is a different and
> less annoying symptom.  I also limit the number of simultaneous jobs
> to two and I hold off commflagging until after the recordings have
> finished.  There appears to be nothing of interest in the frontend
> log.  I occasionally see "ALSA, Error: WriteAudio: buffer underrun"
> messages, but these do not seem to correlate to the pauses.
>
> I am looking for any ideas on how to proceed to troubleshoot this
> problem.  The WAF is not plummeting, but I do get the occasional,
> exasperated question "Why does it do that?" which, unfortunately, I
> cannot answer but desperately want to be able to.
>
> -- Ken E.

 I have experienced some similar impact, mostly watching LiveTV.  I 
 notice specifically at the program breaks on the half-hour or hour that 
 the recording is probably dropping off the livetv storage for the 
 previous show and initiating for the new show.