[mythtv] Ticket #9120: smoother play start

[Mark Spieth]

On 15/02/2011 11:19 AM, MythTV wrote:
>   Mark - these patches seems reasonable and there are no obvious issues in
>   testing. I was however expecting to see more of an impact. I don't for
>   example see any audio packets being dropped in actual usage - from tv to
>   recordings to dvd and bluray.
>
>   Given there have been a number of changes in this area in recent times,
>   can you confirm the patches are still behaving as you expect? (or more
>   accurately, giving the desired benefit)
>
>   thanks and regards, Mark
>
sorry still running behind with my new builds for testing purposes.

It appears that different media streams have different pts/dts 
sequencing between audio and video components.

I have seen streams with audio pts way ahead (like 1 second) of the 
video pts. Even the different dvb channels (SD has variations as well as 
HD) here have different delays/interleaving. As a result the player sees 
1 or more seconds of audio data before the video data with the same pts 
is available. hence the player starts playing the audio, the video 
appears and vsync kicks in to slow audio/speedup video so that they 
become synced, causing annoying effects for the first few seconds of 
play, including after skip.
the converse is also true where video appears first and then audio (all 
broadcast dvb).
thats the theory behind the implementation anyway.

I suspect it is completely independent of the other changes done 
recently in the player.

note this also affects my play to end patch as you have to exhaust both 
video and audio data even though there may be no more of one type for a 
few seconds. this affects avi/mkv playback more than dvb as dvb almost 
always has overruns so you dont care so much.

HTH
mark