[mythtv] 2019-devel: lipsync drift

[John Pilkington]

I'm still seeing this slow drift in my el7 build of  mythfrontend 
version: devel/2019-render [v31-Pre-9dc72f3b810] www.mythtv.org

and it seems likely to be connected to 
mythtv/libs/libmythui/DisplayResX.cpp tweaks at commit b8e27f1039 - and 
perhaps the reported lack of NVCtrl on this system.

$ mythfrontend -v playback,libav

2019-11-27 13:40:22.479018 I  DispResX: Created
2019-11-27 13:40:22.479852 N  DispRes: Desktop video mode: 1440x900 
74.984 Hz
.......
2019-11-27 13:40:27.454064 I  DispResX: Raw/unsorted XRANDR modes:
2019-11-27 13:40:27.454090 I  1440x900  75.00   60.00
2019-11-27 13:40:27.454106 I  1280x1024 75.00   60.00
2019-11-27 13:40:27.454119 I  1280x960  60.00
2019-11-27 13:40:27.454132 I  1152x864  75.00
......

2019-11-27 13:40:27.454312 I  NVCtrl: The NV-CONTROL X extension is not 
available on screen 0 of ''
......
and on frontend closedown

2019-11-27 14:09:28.060362 I  DispRes: Changing to 1440x900 75.000 Hz
2019-11-27 14:09:28.094487 I  DispRes: SwitchToGUI: Switched to 1440x900 
75.000 Hz
2019-11-27 14:09:28.094498 I  DispResX: Deleted

$ xrandr
Screen 0: minimum 8 x 8, current 1440 x 900, maximum 32767 x 32767
VGA1 connected primary 1440x900+0+0 (normal left inverted right x axis y 
axis) 410mm x 260mm
    1440x900      59.89 +  74.98*

=====

In contrast, a build for Fedora 30 at the same commit, with nVidia 
graphics, shows DispResX rates that are the same as those from xrandr; 
not, as above, truncated to the nearest integer.  It also shows 
CustomRate: to 4 decimal places.

This is probably not a  blocker.  DLNA doesn't show the drift.  I 
haven't yet found a logging option that does.

HTH

John P