[mythtv] AVSync2 Improvements

[Peter Bennett]

On 2/12/19 3:59 PM, Mark Spieth wrote:
> On 2/13/2019 3:01 AM, Peter Bennett wrote:
>> I have been using the latest patch 
>> https://code.mythtv.org/trac/attachment/ticket/13383/20190208_1644_catchup_plus.patch 
>> for a couple of days and it looks good now.
>>
>> Mark- you said you may have some improvements - I plan to commit it 
>> anyway and those can always be done afterwards.
>>
>> You said that making the wait into a series of short waits may 
>> improve things. Currently on a desktop system everything is between 
>> -5 and +5 ms so I don't know if much improvement is possible. Also on 
>> thinking about it I don't know how that would help, if the operating 
>> system is going to delay resuming a process on one wait, would it be 
>> less likely to delay it on a bunch of smaller waits?
>>
>> If I don't hear anything back I will commit that patch to master and 
>> fixes/30.
>>
> By all means commit. It seems pretty good to me. Haven't tested live 
> TV since I don't use it but the periodic video stutter is ok. Not as 
> smooth as it could be but pretty good at all speeds so far used. I see 
> on the shield +-20ms which I don't understand ATM. The opensles driver 
> chunks things into 10ms blocks so that is currently the best audio 
> time quantum that is available. Ill look at providing a better 
> estimate which should be possible using the buffer callback and a time 
> delta.
>
> The original AVSync used some averaging/smoothing of the AV delta, so 
> that may be useful to improve playback smoothness. Panning shots and 
> ticks show this effect quite clearly.
>
I added the avsync averaging code to address the problems with OpenMAX 
Audio. AVSync2 is supposed to achieve the same by limiting the size of 
each adjustment to 10 ms or other value as specified in settings. You 
could try changing that to see if it helps.
> Not sure how much the smaller delays affect things. When I get time 
> Ill disable or maybe put in a config and do some A/B tests.
>
> As mentioned before, there may be a timestamp wrap issue but only saw 
> strangeness once and have deleted that program so Ill have to wait 
> until I see it again.
>
The code under "if ((lateness > AVSYNC_MAX_LATE || lateness < - 
AVSYNC_MAX_LATE)" is supposed to address timestamp wrap, which should 
occur without anything unusual being visible. If you have any example 
which wraps I would like to test it and make sure.
> Cheers
>
> Mark
>
I have attached a new patch to the ticket to address the LiveTV problem.

Peter