[mythtv] 2019-devel: lipsync drift

[John Pilkington]

To continue...

I have a 'new' F30 box, i3 4-core with nVidia and a single VGA-driven 
monitor, again running c794391ad. The only recordings at present are 
from assorted iptv channels, but they show no obvious a/v drift.

The DispRes: Desktop video mode on frontend startup and the DispRes: 
SwitchToGUI on exit are both clean 1920x1080 60.000 Hz

John