I have recorded some video tutorials for our programming team. These consist of "live coding" exercises; basically, videos of me coding stuff. Thus, the video track is a screencast, and the audio track is consists of either my voice, or long periods of silence and/or clacking keys.

What I would like to do is to automatically speed up the silent and key-clacky portions of the video, while leaving the parts with voice intact. Unfortunately, I am a video editing novice. So, is there some well-known way to do that ? If not, is there some Python library (or C#/Java library even, I'm not married to Python) that can get me at least part of the way there ?

  • This question on super user may help you. superuser.com/questions/818342/strip-motion-events-from-file
    – kazanaki
    Commented Jul 2, 2015 at 14:57
  • @kazanaki - I edited your comment a bit. While the question linked may be helpful, for purposes of duplicates, the same question coming up on multiple sites isn't considered a duplicate unless the same OP posts both. Basically the expectation is that an OP identify the best place to ask and ask it there, however it is not expected that someone search all the SE sites for their question before posting where they think is best.
    – AJ Henderson
    Commented Nov 2, 2015 at 21:33
  • Yes, I understand what you are saying.
    – kazanaki
    Commented Nov 3, 2015 at 8:31

1 Answer 1


It might be possible through scene detection if your editor of choice allows for scene detection based on sound. Alternately, since you are obviously handy with code, you could use a video editing library to write a program that would look for a threshold audio level to be exceeded and look for any long periods of time with no such peaks. You could then apply speed changes between those timestamps.

The actual coding of something like that is really more of a programing question than a video production question, but it should be technically possible using that kind of a technique. I'd recommend looking at libav or one of the similar types of windows libraries for manipulating AV files.

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