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

[Peter Bennett]

On 10/30/18 5:53 PM, Andreas Mayer wrote:
> On/Tue Oct 30 16:19:39 UTC 2018/  Peter Bennett <pb.mythtv at 
> gmail.com <http://lists.mythtv.org/mailman/listinfo/mythtv-dev>> wrote:
>> I have added some checkboxes in the video playback advanced settings to
>> disable certain pixel types. You can try disabling one or both of those
>> to see if the results are any better. These are mainly useful for
>> android and low powered systems but they may make a difference.
> Disabling YV12(YUV 4:2:0) and UYVY(YUV 4:2:2) pixel format did not 
> make any difference for VAAPI2.
>
>> Please can you supply a sample video to test VAAPI and VAAPI2 issues. I
>> will see if there is a way to improve the CPU requirements so that
>> vaapi2 and avsync2 give a good result.
> Will send PM ...
>
> mythffmpeg -i hevc_test.ts
> Input #0, mpegts, from 'hevc_test.ts':
>         Duration: 00:02:47.65, start: 44350.528844, bitrate: 4602 kb/s
>         Stream #0:0[0x1ff]: Video: hevc (Main 10), yuv420p10le(tv, 
> bt2020nc/bt2020/arib-std-b67), 3840x2160 [SAR 1:1 DAR 16:9], 50 fps, 
> 50 tbr, 90k tbn, 50 tbc
>         Stream #0:1[0x200](DEU): Audio: aac (LC), 48000 Hz, stereo, 
> fltp, 192 kb/s
>
> I'm using a playback profile with filters, OSD fading and 
> deinterlacing disabled, avsync2 enabled and mythavtest for playback 
> (on a 1920x1080 at 50 display)
>
> With VAAPI video and audio looks OK (although with -v playback you can 
> see frames being dropped), intel_gpu_top shows 90-98%
> With VAAPI2 only a few video frames are shown every few seconds, 
> intel_gpu_top shows low gpu utilization.
>
> Thank you,
> Andreas
>
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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.

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.

Peter