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Youtube has an option to change the playback speed of videos that speeds up or slows down a video's audio without affecting its pitch. I know that there are a number of different algorithms that can do this, but I am curious as to which specific algorithm Youtube uses because it seems to work rather well.

Also, are there any open source libraries implementing this algorithm?

nellapizza
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    A few years ago they were using a version of the PICOLA algorithm in some apps. The iOS app might have also used the built-in iOS TimePitch Audio Unit. – hotpaw2 Jan 27 '20 at 20:16

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I found this article on the subject dating back to 2017, I presume it's still valid or should give you some pointers: https://www.googblogs.com/variable-speed-playback-on-mobile/

It reads, in part:

"On Android, we used the Sonic library for our audio manipulation in ExoPlayer. Sonic uses PICOLA, a time domain based algorithm. On iOS, AVplayer has a built in playback rate feature with configurable time stretching."

Jeff Schaller
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Mimakari
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