[mythtv-users] Debugging mythfrontend video freeze

Scott D. Davilla davilla at 4pi.com
Wed Nov 28 22:57:51 UTC 2007

I've asked this on mythtv-dev and got silence. So I figure I'll try here.

I'd like to get some help in debugging a frontend video freeze. I'm
using svn version 14938 trunk builds. Setup is as follows;

	Dedicated backend w/ two PVR-150 and a dual channel
HDHomeRun. So 4 encoders. This is all mpeg2 encoding. Backend has
plenty of resources (core2 du0 at 1.83 GHz with four SATA 500GB
drives for video storage and 320GB boot. Runs same svn version.

	1GHz Pentium-M with nvidia 7300 for mpeg2 hardware decoding.

This setup works quite well in handling HD content from the
HDHomeRun, video is nice and smooth and cpu percent is 60-70 when
displaying 1080i or 720p ATSC HD content. The frontend has no problem
displaying HD content besides the below problem. I do have other 
frontends (both x86 linux and x86 OSX) that don't have the below 

The problem is I get random frontend hangs where the video freezes. 
Yes this is during LiveTV viewing.
Escape key works in that the frontend tells the backend it is done
but frontend must be killed to fully recover as it's still hung
somewhere. The freeze is very random, sometimes in minutes, sometimes
hours. Smells like a random race condition.

I've run full logs on both sides and there is no indication of any
errors, I can see the last transfer request from the frontend,
backend gets it and sends, frontend seems to get the transfer but
there are no more transfer requests from the frontend. It's as if the
frontend is waiting for something to complete. I am getting frontend
prebuffering pauses but from what I can trace in the code, the
frontend has run out of frames to feed to the decoder. So why did the 
frontend run out of frames and why is it not asking for more from the 

So I'm looking for a better understanding of the frontend process of
getting video data from the backend, buffering and decoding, etc.. so I can
figure out where to start debugging the freeze.
I'm viewing 1080i HD content from ATSC source. I can stick debug outputs
and build and test but I'm looking a assistance in where to start
looking and placing printouts so I can track this freeze down and fix


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