[mythtv-users] Match display refresh rate to video framerate

Jean-Yves Avenard jyavenard at gmail.com
Mon Dec 28 03:45:20 UTC 2009


2009/12/28 Schuren, Mark <schurenmark at versanet.de>:
> - In the relevant mythfrontend settings page I choose 1920x1080 for the gui
> and video resolutions and "Any" for the refresh rate to enable the automatic
> mode adjustment. BUT: browsing the available frequencies there does NOT show
> me "24.0", "50.0" or "60.0" Hz, but gives me the following choices "23.919 Hz",
> "49.832 Hz", "59.719 Hz", "59.798 Hz" or "Any".

I missed that part.

The refresh rates showing in MythTV is what is calculated from the ModeLine.
So while nvidia shows it as 24Hz in the nvidia-settings it really is 23.919Hz

It looks like the algorithm to select what best refresh rate is usable
fail in your case because 49.832Hz is too far away from 50Hz.

the reasons for the code for not picking up 49.832Hz was that I had to
give a pretty narrow interval checking to be able to differentiate
60Hz from 59.97Hz which is what the US really uses...

So when selecting what the best refresh rate is ; it first tries all
refresh rates with 0.1 accuracy. If that fails it tries to round to
the next integer (so that 59.97 shows up as 59 and 60 as 60).
49.832Hz as such is picked up as 49Hz which doesn't match 50Hz as far
as the code is concerned.

I will have to investigate this further.
I've never seen refresh rates so far off the real thing.

In the mean time ; you could check on my site for a xorg.conf that
defines the proper refresh rates, so no more of this 49.8Hz garbage.

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