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

Schuren, Mark schurenmark at versanet.de
Mon Dec 28 00:56:38 UTC 2009

Hi list,

is anyone using the 'Frame rate: Any' setting in Myth for matching the
refresh rate of the display to the video frame rate automatically? Is
anyone successful with 25fps/50Hz content/modes?

I struggle with it for quite some time now. I'm in PAL land, so most of
my recordings are 25fps and require a 50Hz mode for best performance,
but in my setup mythtv never picks the 50Hz mode correctly :(
It correctly picks a 24p mode when watching 24p content however, and it
correctly picks a 60 Hz mode for 30 or 29.9 fps material correctly.

Unfortunately it always picks 60Hz for my 25fps recordings. The recordings
are from DVB-T and DVB-C (in Germany), and I get no luck with both
progressive and interlaced recordings. Resolution of the video is also
not relevant, since myth picks the 60Hz mode for EVERY recording, even
PAL (progressive) DVDs or other PAL video material. Example mythfrontend
log (-v playback) shows:

2009-12-28 00:54:09.001 VidOutVDPAU: VDPAU Colorkey: 0x20202 (depth 24)
2009-12-28 00:54:09.007 *** Trying to match best refresh rate 25Hz
2009-12-28 00:54:09.007 Trying 1920x1080 59.798 Hz
2009-12-28 00:54:09.011 Dynamic TwinView rate found, set 59.798Hz as XRandR 52
2009-12-28 00:54:09.012 SwitchToVideo: Video size 720 x 576: 
    Switched to displaying resolution 1920 x 1080, 488mm x 274mm

So mythfrontend detects 25fps video, but picks "59.798Hz" for the display

My setup is
- NVIDIA ION with Sharp Aquos LC-46XL2 1080p LCD TV (via HDMI).
- Mythbuntu (Karmic) x64 with JYA's testing repo (currently 0.22-fixes 23003).

I've made no major modifications to xorg.conf regarding custom modelines.

What confuses me: 

- nvidia-settings lets me select a couple of modes for my TV, allowing me
1080p with 24Hz, 50Hz or 60Hz refresh rate, and 1080i with 50Hz or 60Hz.
I guess that's what comes from the TV's EDID. All these modes work fine when
selected manually in nvidia-settings.

- xrandr shows 'stupid' rates, but mythtv should handle that correctly, as I
read this http://svn.mythtv.org/trac/changeset/21489 and this 

- 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".

- 'Any' does work for 24p and e.g. NTSC-based content, but does NOT work for
25fps (PAL) content.

- '49.832' (instead of 'Any') does work for 25fps content only. The "override"
settings do not work for me anymore since upgrading to 0.22. So this setting is
just as good as disabling the automatic feature.

- xvidtune tells me that my 50Hz modes do have EXACTLY 50.00 Hz refresh rate,
when I select them manually in nvidia-settings.

So, I guess the root cause is that mythfrontend shows these odd frequency
numbers in the settings page (where does it get them from??).

Anyone in PAL land who can confirm this? Anyone having this working??

Further ideas, please? Should I raise a ticket in Trac?


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