[FFmpeg-devel] Re: [PATCH] WIP: avfilter: add Bungee audio stretch filter (PR #20697)

[john--- via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

Thank you for taking a look. Bungee is the result of independent research and optimisation. It was released in Feb 2024 as MPL v2.0. Bungee Pro was released alongside Bungee: although it shares an API, its algorithms are proprietary, its audio quality is industry leading and it is highly optimised for web and mobile platforms.

I don't like to compare to other implementations, but since you asked, Nicolas, here are three main differences between libbungee and librubberband:
1. Bungee is a new and different algorithm. In my opinion, the audio quality is improved in many situations, avoiding some of librubberband's artifacts. Here is a random example at 56% input tempo, taken from the comparison page on the Bungee site:
https://bungee.parabolaresearch.com/audio/bungee/wrong-0.56-0.aac
https://bungee.parabolaresearch.com/audio/rubberband/wrong-0.56-0.aac
That said, such comparisons are subjective and very dependent upon the input audio and on the listener. And Bungee is still far from the perfect time stretcher (Bungee Pro is closer but I'll not say more about that...) 
2. Bungee can be faster than rubberband: 1.7x faster in a quick test on Mac M4 of a tempo change to 56% of original tempo
3. Bungee has a different license: MPL-2.0 which is compatible with LGPL-2.1. librubberband is GPL-2.0 which requires --enable-gpl

This PR is an offer of maybe useful code and I won't be at all offended if Bungee and FFmpeg are not a good fit at this time.

John
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