How to cut a video file on black keyframes

extract_video.sh

# Re-encode source video with one keyframe every 5 frames
ffmpeg -i source.mkv -g 5 tmp.mkv

# Search black frames
ffmpeg -i tmp.mkv -vf blackframe -f null -

# Use output to locate black frames right on keyframes
# Then cut video at those keyframes
ffmpeg -i tmp.mkv -ss 6.089 -to 180.263 -c copy tmp2.mkv

# If the audio is not in sync with the video, detect silence
ffmpeg -i tmp2.mkv -map 0:1 -af silencedetect=d=.1 -f null -

# Use output to decide where to cut the audio
ffmpeg -i tmp2.mkv -map 0:1 -to 173.22 -c:a copy tmp2.ogg

# Merge reencoded video and shortened audio back together
ffmpeg -i tmp2.mkv -i tmp2.ogg -map 0:0:0 -map 1:0:1 -c:a copy -c:v copy output.mkv