[mythtv-users] Prebuffering Pause and memory

Brad DerManouelian myth at dermanouelian.com
Thu Aug 28 20:59:14 UTC 2008

On Aug 28, 2008, at 1:46 PM, Michael Wisniewski wrote:

> Thanks for the response.  I don't want to beat a dead horse because I
> know that this has been brought up many of times.
> Since it's not swapping (according to the 'free -o' command), then
> poor disk i/o can be ruled out.

Just because you're not swapping doesn't mean your disk is definitely  
delivering the data fast enough. Probably is, but not certainly.

> It's all on the local machine, so I
> can rule networking out.  Finally, I don't believe it to be bad source
> material because the source is fine.  So, what else can it be?

CPU could be too slow.

> For what it's worth, it usually only seems to pop up if I'm in the
> guide or right after I change channels.  After a few minutes of
> watching hte program after changing channels, it goes back to normal.
> Now with HD content, it seems to happen more often along with jagged
> motion (not pixelation).  The jagged motion almost looks like it's due
> to a high utilization in the processor and/or memory/swap.

Yup. Your deinterlacer is using lots of CPU cycles when there's lots  
of movement.
Also, if you're using a double frame-rate deinterlacer like Bob  
(notice the X2 next to it) it means it's trying to read a frame ahead  
of what's displaying to see how the deinterlacing should happen  
between the frames. That's a lot to ask of a CPU and disk when you're  
dealing with very big video files.

Do you get the prebuffering pauses on 720p or 1080p content or simply  
when you turn off the deinterlacer manually?

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