[mythtv] AVSync2 Improvements

Mark Spieth mark at digivation.com.au
Fri Mar 1 22:28:52 UTC 2019

On 3/2/2019 7:21 AM, Peter Bennett wrote:
> On 2/28/19 4:10 PM, Mark Spieth wrote:
>> I watched too last night with the patch using mediacodec however I 
>> had it on old AVSync but the finish early issue still existed which 
>> is strange too.
> The "finish early" fix only applies to AVSync2. See comment 1 in the 
> ticket.
>> Will have to repeat tonight with AVSync2.
>> I can make some programs available again if it helps Peter. Use my 
>> previous link but use recordings/1020_20190228080000.ts (news last 
>> night) or some of the other recent ones. The one listed is guaranteed 
>> to show the issue. 1020 is HD and 1021 is SD.
> I will try that one. Does it always glitch in the same place?

I dont see any glitches at all during playback of any of these programs. 
The time is just wrong but this also does not happen linearly. My test 
last night with AVSync2 worked well except I had mythcommflag suck 21g 
out of my ram bringing the whole backend to a grinding halt until I 
deleted the errant process, but thats another/different problem. 
Playback on the shield paused at that period but the timestamp was 
correct at that point. I thought originally that the deletemap search 
for the timestamp had an infinite loop but I suspect that is wrong, but 
more testing will ensue today.

There are others too. anything with a channel number in 10xx is a dvbt 
recording. I have left some around for this purpose (testing/validation).

> I did see a period of stuttery playback during David's recording while 
> I was testing the finish earky fix. The thing is, during the stuttery 
> playback the system was unresponsive to the remote. This indicates 
> that something on the system was pre-empting mythfrontend.
I had a different problem the other day where with mediacodec with both 
AVSync and AVSync2, both exhibited a play 1sec then skip 1 sec type 
behaviour which was really weird. Unfortunately I deleted that without 
thinking after playing successfuly with SW decode. This may be the same 
as the stuttery playback but not sure. Only ever happened once, on a 
program I watch weekly.

> What springs to mind is that it may have been doing a java full 
> garbage collect operation. My experience with java (non-android) is 
> you need to be careful to avoid full garbage collect operations during 
> a real-time process like playback. Mediacodec decoding goes through 
> java code so it may be a possibility. I don't know how you adjust the 
> garbage collect settings on android, on regular systems it is via 
> parameters on the java command line.
I dont either, but if this was a problem, other apps would have seen 
this too. Unlikely cause.
> Do you notice that it is unresponsive to the remote while the 
> stuttering takes place?
No. But I have only seen it once.


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