[mythtv] DRM VSync

[Ivor Hewitt]

I have a drm vsync question....

I'm currently getting myth working on a VIA CN400 unichrome-pro board... 
the current problem I've got is that the mythplayer is running away with 
itself and seems to have problems with the drm timing calculation.

A log from a cn400 (@75Hz) playing back a 25fps PAL broadcast shows:-
2005-04-01 09:45:30.718 Video timing method: DRM
2005-04-01 09:45:30.718 Refresh rate: 40000, frame interval: 40000
'video_output' mean = '13661.89', std. dev. = '4427.53', fps = '73.20'
'video_output' mean = '13365.44', std. dev. = '578.30', fps = '74.82'

The same video on a CLE266 (@60Hz) shows:-
2005-04-01 09:48:11.850 Video timing method: DRM
2005-04-01 09:48:11.850 Refresh rate: 16669, frame interval: 40000
'video_output' mean = '39239.88', std. dev. = '8932.58', fps = '25.48'
'video_output' mean = '40000.95', std. dev. = '8204.02', fps = '25.00'
'video_output' mean = '40002.02', std. dev. = '8206.91', fps = '25.00'


i.e. on the cn400, the initial drm check seems to have decided that the 
refresh rate matches the video rate... but it's actually 75hz so it has 
run off and played at 75hz. With inevitable results.


This is not a Myth problem and bound to be a driver problem, but I 
wondered if someone who knew how the DRM calculation code worked could 
suggest why it would have concluded that the refresh rate matched rather 
than just failing.


-- 
Ivor
http://www.ivor.it