[mythtv] AVSync2 Refinements

Mark Kendall mark.kendall at gmail.com
Thu Dec 19 08:25:55 UTC 2019

On Wed, 18 Dec 2019 at 14:48, Tim Pletcher <pletchtd at gmail.com> wrote:


So the first issue was self inflicted - I've added a better fix for
MHEG only files that doesn't break audio only.

> In the second and third cases you mention above, does the timestamp data provide any clues as to what is occuring?
> To provide better visibility of what is going on, I have been patching mythplayer lib to also emit the lastfix value with the timestamp data when I wish to troubleshoot.  I also hacked together this simple bash script (attached) to parse the data into a comma delimited text file for easier viewing of the data in a spreadsheet program.

Thanks - I forgot to ask if I could get that script. I'll try and pull
out some data when I can - visitors arriving for Christmas today...

> I have been thinking about implementing a simple adaptive filtering / control algorithm which would dynamically adjust the filtering coefficient between an upper and lower bound based on the standard deviation of the sync calculated over a shifting window of frames.  I believe the comments from Mark S earlier in this thread also essentially propose an adaptive filter approach but I need spend some time examining.  On the flip side, I am hesitant to add complexity if not needed / really valuable.

I'm open to further improvements but I think we need to let the
current code settle for a while - and if there are no reported issues,
perhaps refine it after 0.31 is out.

> If you send me some frontend log data with timestamps, I'd be happy to look over in order to see if the data suggests these are control problems or caused by something else.

Thanks - I will do that:)


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