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A command-line clapperboard

Project Description

Want to record yourself playing over a backing track but want to use your quality soundcard input instead of your camcorder’s crappy audio? No problem, we’ve got you covered!

Clapperboard is a thin wrapper around MoviePy that lets you synchronize your video and audio by using a clapperboard-like technique. If you don’t know what I’m talking about, have a look at this post ->

Instead of using a pricy UI based NLE, you can instead use this handy command line script to sync your video and audio tracks.


Clone this repo and run pip install clapperboard.



Once you figure out the precise moment where you made your “clapperboard” sound with your instrument for both tracks, you can replace your video’s audio with your real audio track by running clapsync.


clapsync audio_filename video_filename video_start audio_start out_filename


clapsync guitar_solo.mp4 guitar_solo.wav 15.32 2.45 guitar_solo_sync.mp4


Once you’ve sync’d your video and audio tracks, you may want to remove the part of the video where you signal with your “clapperboard” sound (apart from the part of the video where you stretch yourself onto the keyboard to stop recording). Clapperboard comes with another utility that lets you crop the video from both sides and (optionally) add fadein/fadeout effects.


clapcrop filename out_filename start_seconds end_seconds fadein_seconds fadeout_seconds


clapcrop guitar_solo.mp4 guitar_solo.mp4 2 49 1 3


  • PEP8 cleanup
  • Command-line arguments cleanup

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