[FFmpeg-user] h264_vaapi missing frames

[Kai Hendry]

Hi there,

With my brand new Intel 8th gen laptop (Intel Corporation UHD Graphics
620 (rev 07) with 8 core Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz on
Archlinux, I thought I'd experiment with hardware accelerated capture
as opposed to my normal 2-step approach of
1) recording to mkv
https://github.com/kaihendry/recordmydesktop2.0/blob/master/x11capture
2) converting mkv to mp4
https://github.com/kaihendry/recordmydesktop2.0/blob/master/htmlvideo


However with -vaapi_device /dev/dri/renderD128 -movflags +faststart
-vf 'format=nv12|vaapi,hwupload' -c:v h264_vaapi it seems to skip
frames.

https://s.natalian.org/2018-03-20/1521512464.mp4.log
https://s.natalian.org/2018-03-20/1521512464.mp4


Ffprobe seems to say it's 30fps:
 Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
2560x1440, 722 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc
(default)

But during playback, it would appear not!

Is there a good way to test or know I've dropped frames in my screen capture?

How can I prevent frame dropping?

Kind regards,