What algorithm does YouTube use to change playback speed without affecting audio pitch?

Question

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?

Amorous

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. – Golgotha

Answer 1

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."

Eire