Hardware does not support encoding at size 4992x3744

Like Apple's Live Photos, Panasonic offer a similiar feature called 6K Photo Mode.

However the output file, for example https://s.natalian.org/2019-05-02/P1077291.MP4 as ffprobe (part of ffmpeg) will tell you:

Video: hevc (Main 10) (hvc1 / 0x31637668), yuv420p10le(pc, bt709), 4992x3744 [SAR 1:1 DAR 4:3], 187160 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc (default)

No application seems to natively playback this video file. Except maybe PotPlayer, but I do not have Windows OS to try. GH5's native OS is just too slow IMO to pick out a good image on the small display screen.

mpv

The common open video player called mpv is unable to play back P1077291.MP4 smoothly.

Normally I would to expect to step through this video and hit s for screenshot. It works but it's too slow to do on my T480s Thinkpad.

Audio/Video desynchronisation detected! Possible reasons include too slow
hardware, temporary CPU spikes, broken drivers, and broken files. Audio
position will not match to the video (see A-V status field).

ffmpeg

When using hardware accelerated video encoding/decoding VAAPI you will hit:

Hardware does not support encoding at size 4992x3744

When trying to re-encode it, it fails:

https://s.natalian.org/2019-05-02/P1077291.mp4.log

With hardware features disabled you can successfully re-encode in software and vastly more workable video will look like:

Notice the fps reported if 30fps, but it certainly doesn't feel like that in playback. Why?

Nonetheless, step {forward,backward} in mpv maxes my 8th gen Intel T480s!!

Why?