CodeAnim

Click to see demo:

TODO:

• Hold button -> repeatedly apply the action (step / fast forward)
• Scroll the timeline when jumping
• Audio track to play under the video?

Recording with FFMPEG:

• ffmpeg -video_size 1920x1080 -framerate 60 -f x11grab -i :0.0+0,0 no-settings.mp4 ~ 811 kB
• ffmpeg -video_size 1920x1080 -framerate 60 -f x11grab -i :0.0+0,0 -c:v libx264 -preset ultrafast -crf 0 crf0-ultrafast.mp4 ~ 18 MB
• ffmpeg -i test2.mp4 -c:v libx264 -preset veryslow -crf 0 crf0-ultrafast-then-crf0-veryslow.mp4 ~ 3.5 MB
• ffmpeg -video_size 1920x1080 -framerate 60 -f x11grab -i :0.0+0,0 -c:v libx264 -preset ultrafast -crf 17 crf17-veryfast.mp4 ~ 3.3 MB

The first option is surprisingly readable, given it's 330 kb/s. The third option (that is, first ultrafast CRF=0 then veryslow CRF=0 as a second pass) looks like the best guarantee of real lossless output. And there seem to be no frame drops.

Note: On FFMPEG wiki I found out I should use libx264rgb instead of libx264, so that it doesn't convert lossily to a different colorspace.