[mythtv-users] Kernel options, Preemption model and Timer frequency

Peter Bennett pb.mythtv at gmail.com
Sat May 12 23:55:38 UTC 2018



On 05/12/2018 04:49 PM, Rajil Saraswat wrote:
> I am chasing Audio/Video sync problems, and was wondering what are the
> best kernel options for the BE server. Amongst the three preemption
> models (CONFIG_PREEMPT_NONE, CONFIG_PREEMPT_VOLUNTARY, CONFIG_PREEMPT)
> which is the best choice. Likewise for Timer Frequency ( CONFIG_HZ_100,
> CONFIG_HZ_250, CONFIG_HZ_300 and CONFIG_HZ_1000), which is the best choice.
>
> At the moment on the FE i am seeing errors like so during LiveTV,
>
> 2018-05-12 15:44:39.163391 N  Player(0): Waited 4177ms for video buffers
> AAAAAAAAAAAUUUUUUUUUUUuLAAAAAAAP
> 2018-05-12 15:44:39.180607 I  Player(0): Video is 11438.3 frames behind
> audio (too slow), dropping frame to catch up.
> 2018-05-12 15:44:39.180639 I  Player(0): Video is 20016.2 frames behind
> audio (too slow), dropping frame to catch up.
> 2018-05-12 15:44:39.180649 I  Player(0): Waiting for video buffers...
> 2018-05-12 15:44:39.281204 N  Player(0): Waited 101ms for video buffers
> AAAAAAAAAAAAAAUUUUUUUUUUuAAAAAAP
> 2018-05-12 15:44:39.321036 I  Player(0): Video is 26449.5 frames behind
> audio (too slow), dropping frame to catch up.
> 2018-05-12 15:44:39.321056 I  Player(0): Waiting for video buffers...
> 2018-05-12 15:44:39.325482 I  Player(0): Video is 31274.3 frames behind
> audio (too slow), dropping frame to catch up.
> 2018-05-12 15:44:39.325501 I  Player(0): Waiting for video buffers...
> 2018-05-12 15:44:39.344897 I  Player(0): Video is 29468.8 frames ahead
> of audio,
>                          doubling video frame interval to slow down.
>
> Thanks
>
> _______________________________________________
>
It seems to be suffering from very slow decoding of video. Check your 
playback profile and whether it can use hardware decoding for the type 
of video. If it is a high end Frontend machine as you say, this should 
not happen, even without hardware decoding. I suggest run top and see 
what the cpu usage is, and if it is doing swapping.

Peter


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