[mythtv-users] Prebuffering Pause and memory

Michael Wisniewski wiz561 at gmail.com
Fri Aug 29 00:58:13 UTC 2008


Hmmm....  I believe that you might be onto something.  I have been
using XvMC because all of the other choices seem to really crank up
the utilization on the xorg process and the mythfrontend.  With XvMC
enabled, it seems to hover around 20% utilization.  Without XvMC and
using another method, it hovers in the 90's.  Since I don't really
know what the differences are between all of the choices, I don't
really know which one to choose, so I just use XvMC.

One message I see frequently in the mythfrontend logs are...

---
2008-08-27 21:38:25.059 Couldn't load deinterlace filter none
2008-08-27 21:38:25.059 Using deinterlace method
---

I didn't really think about it, but since you mentioned the
interlacing, it makes me wonder if it's related to the problem.  Which
then leads me to investigate things a little further and add an
update.

============
UPDATE:  I did some research and looking around.  I also played around
with the playback mechanisms (ffmpeg, XvMC, via XvMC, etc) and the
deinterlacing.  It seems like when I turn XvMC off, I don't really get
the jump video and the prebuffer pauses while watching a show.  What I
did is use the ffmpeg playback mechanism and turn deinterlacing off.
If that causes problems with the picture, I think I'll probably turn
it back on and play around with that.

For others that are having the same problem, I *highly* recommend
trying ffmpeg for playback INSTEAD of XvMC even if you have a nvidia
card!  Also, check out the mythfrontend log files in verbose mode!  I
found out that I was getting a RTC permission denied error message
which was fixed by issuing...

echo 1024 > /proc/sys/dev/rtc/max-user-freq

The SD video does look a little strange (blurry, not as 'crisp' as
non-myth viewing), but I believe that it has something to do with the
deinterlacing.  Probably over time, I'll figure it out.  But until
then, if you're having issues with prebuffer pauses, I'd recommend
trying ffmpeg for playback.

Thanks again for everybody's help.


On Thu, Aug 28, 2008 at 3:59 PM, Brad DerManouelian
<myth at dermanouelian.com> wrote:

> 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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