Prior to changing settings, consider if a separate profile should be used. Duplicating the current OBS profile can be done with Profile > Duplicate....

OBS screenshot. The profile tab is expanded with the cursor hovering over the duplicate button.

Simple

  • In the output tab in settings with “Output Mode” set to “Simple”. Use “Lossless Quality” preset on the recording section.

  • On the advanced tab, set “Color Format” to “I444 (8-bit, 4:4:4, 3 planes)”.

Videos will be recorded in .avi format if this is done.

Advanced lossless H.264

  • Ensure that in the output tab in settings with “Output Mode” is set to “Advanced”.

  • Switch over to the “Recording” tab.

  • Set options in the “Recording Settings” section:

  • Set options in the “Encoder Settings” section:

  • On the advanced tab, set “Color Format” to “I444 (8-bit, 4:4:4, 3 planes)”.

Re-encode

Whichever way the video is encoded, it may not exactly be tightly compacted. For this, it may be recommended to re-encode the recorded lossless video.

ffmpeg -i "./input-video.mp4" -codec:v libx264 -codec:a copy -preset placebo -qp 0 "./output-video.mp4"

If -preset placebo is too slow. Try -preset veryslow.

Verify (frame extraction)

Check that these lossless videos are in fact lossless. I do this by extracting frames and manually checking them. Using FFmpeg, this command can be used:

ffmpeg -i "./video.mp4" ./frame%04d.png