[mythtv-users] Strange Playback behaviour

Peter Bennett pb.mythtv at gmail.com
Mon Oct 8 14:27:33 UTC 2018



On 10/08/2018 04:45 AM, Andy Smith wrote:
> Hi All,
>
> Can I recall for a moment something mentioned in another thread -
> "MythTV Light installation" :-
>
> On Sun, 7 Oct 2018, 12:25 James Abernathy <jfabernathy at gmail.com> wrote:
>
>> The video seems to occasionally speed up and slow down like when a person is
>> walking across the screen.  It's like then the sport replay guy is messing with
>> the speed of replaying a touchdown run.
>> The audio does not sound different and there is no pitch change. It's also is
>> correct lip sync.
> I am seeing exactly the same behaviour but with Ubuntu 18.04  and
> v29.1-38-gb9c5f8b delivering to a Samsung TV via a HDMI connection on
> a GT218 [GeForce 210].  I have tried a number of different playback
> profiles, OpenGL Slim seemed to display this effect the least but
> doesnt eliminate it.
>
> I have been mytwaiting for an opportunity to upgrade that video card
> then I spotted this post and thought I would mention it now in case
> this is not hardware related and there is some setting I should tweak
> that I have not picked up on yet.
> Thanks
The speed up and slow down problem is likely related to the audio. It 
tries to vary the video rate to keep in sync with audio. If it is 
getting bad audio timestamps or bad information from the audio driver 
this can happen. Run with -v playback and look at the log for 
confirmation. If this is the case I suggest trying different audio 
settings. Also there is a setting you can try. Run mythfrontend with -O 
AVSyncAveraging=60. The minimum and default value is 4. You can try 
different values. Higher values will smooth out the speed changes but 
may cause lip sync problems.

Peter


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