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

Andreas Mayer and.mayer at aon.at
Tue Nov 6 21:25:07 UTC 2018

On Wed, 31 Oct 2018 15:26:46, Peter Bennet wrote:

> I tried your sample video and I see the same thing. VAAPI2 performs very 
> poorly. In fact, it plays way better using software decoding (opengl 
> slim with number of cpus increased to 4). Something strange is happening 
> with VAAPI2. I will look into that.

I tried your last commit (ticket 13345) today and the results for VAAPI2 are much better than before (but still worse than for VAAPI)
I'm using a Gigabyte Z370M-D3H mainboard with a i3-8100 quad core processor and 8GB memory for testing.

top: mythfrontend 80%
intel_gpu_top: render busy 50%, GAM 75%, CS 50%, TSG 40%, VFE 35%, GAFS 20%

top: mythfrontend 45%
intel_gpu_top: render busy 90%, GAM 97%, CS 90%, GAFS 12%

> Another thing is that probably MythTV is losing some color information. 
> It is converting 10 bit color to 8 bit color. There needs to be some 
> change in the OpenGL codes that displays it, to support the 10 bit 
> color. I believe I can see a difference in colors between playing the 
> video with VLC and playing it with MythTV. I don't know what it takes to 
> support 10bit color with openGL.
I'm still unsure if the Intel driver for Linux currently supports 10bpc, although it looks like there are some changes in Mesa to support 10bpc.
Until now I was not able to get an Opengl test program working with 10bpc.
Gigabyte mainboard with i3-8100 has only HDMI 1.4 output (limited to 4K at 30), my LG TV supports "HDMI UHD Deep Color" only at 4k at 50-60 with YCbCr 4:2:0 or 4:2:2)
Tried an Asus mainboard with i5-6600 (no HEVC main 10 decoding) and external DP to HDMI 2.0b converter and Nvidia GT 1030(Pascal) card installed (DP 1.4 and HDMI 2.0b output, no Linux VDPAU decoding support for HEVC main 10), but had no success until now.

Thank you,

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