[mythtv] 50fps video playback on 30Hz display (4K on HDMI 1.4 output)

Andreas Mayer and.mayer at aon.at
Tue Oct 23 17:07:54 UTC 2018


I noticed that playback of videos with 50fps (for example HD 720p) on a 
display using 30 Hz refresh rate does not work (results in slow motion 
video with stuttering audio).
I agree that this sounds like something one does not want to achive 
anyways, but I recently bought a 4K TV and I am using a mainboard with 
only HDMI 1.4 output (Intel Coffee Lake processor with no LSPCon for DP 
to HDMI 2.0 conversion), so I'm currently only able to use a maximum of 
3840x2160 at 30 for 4K playback (I'm using VAAPI(2)).

Do you think there would there be an easy way to change mythplayer to 
allow playback of videos with higher frame rate than the refresh rate of 
the display (maybe using the new avsync2 code - have not tried that 
yet), maybe by just dropping video frames if there is another frame that 
has to be displayed until the next display refresh occurs?

I'm able to reproduce even with 1920x1080 by switching the display rate 
to 30Hz when watching a 50fps video.

I would own a Nvidia GT1030 card as well (which has DP 1.4 and HDMI 2.0 
outputs), but currently there is no HEVC Main 10 hardware accelerated 
video playback available with Mythtv for Nvidia (VDPAU has no HEVC Main 
10 support, currently there is no CUDA/NVDEV support available for 
Mythtv, would be harder work to implent this one).

Any ideas, comments welcome ...

Thank you,

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