[mythtv] Jerkiness with double rate deinterlace

[Peter Bennett]

Hi David

I looked at your output (https://pastebin.com/69KzcQqr) and it seems the 
deinterlacer is working correctly. The problem seems to be that the 
"predict drop frame" keeps dropping frames. The frame rate is 60 and the 
refresh is 60 but it still drops so many frames. I have noticed the same 
thing but only in certain recordings. In some cases it only drops frames 
during the show and not during the commercials, in some cases during one 
commercial and not during another. This deinterlacer, like the shield, 
is treated as a 60fps progressive stream and does not use the 
m_double_framerate indicator in playback. The gl hardware 2x 
deinterlacer is treated as a 30fps stream and uses the 
m_double_framerate and does not drop frames.

I wonder what the consequences would be of using a different sync method 
than DRM and/or skipping the "predict drop frame" process.

Perhaps the predict drop frame can be adjusted.

One thing may be relevant - the deinterlace filters introduce garbage 
pts values in the deinterlaced frames so I added logic to insert a good 
value there. On the first frame copy the input pts and on the second I 
add half the interval. Perhaps something about that is incorrect or 
inconsistent with the predict drop frame. I will look at this a bit more 
and try some other things.

Peter