Crash with kmsgrab, vaapi_scale and hwdownload

[0x53ee71ebe11e]

While trying to figure out another problem (#8377, may or may not be related), I came upon this crash:

ffmpeg_g -v 9 -loglevel 99 -f kmsgrab -framerate 60 -i - -map 0 -vf 'hwmap=derive_device=vaapi,scale_vaapi=960:540,hwdownload,format=bgr0' -c:v h264 -preset veryfast /tmp/output.mp4

I changed the command line from over in that other ticket. The idea was to skip the hardware encoder and use the software encoder instead after scaling down the source on the gpu. And I was greeted with a crash. See attachement.

Leaving out the scale_vaapi filter works without crash.

I am not sure if using scale_vaapi without using the vaapi encoder afterwards is even a valid thing to do, but it shouldn't crash no matter what.

[0x53ee71ebe11e]

Whoops, I accidentally created this ticket twice