pbmahol

What is latest sox release? Why you ignore all ffmpeg audio filters?

Unrelated, but my C++ solution: https://github.com/richardpl/lavfi-preview

What technical issues?

You can not just preserve original phase when doing time stretching, there are "smarter" algorithms that try to derive "correct" phase, while the paulxstretch just make it random values, maybe for extreme stretching values it doesn't matter for ambient music but for general music and sounds its not that trivial.

There are better, pro solutions, but if you want random phase what that algorithm actually does I'm not going to judge you.

The paulxstretch completely obliterates phase component of audio input. Its not really way to do it if you want real output.

I'm working on https://github.com/librempeg/librempeg

imagemagick does not support RAW video formats.

see lavfi-preview on github. Its GUI app for libavfilter/FFmpeg filters

Is there scientific proof of above claim such as "WASM sandboxing is pretty good!" ?

At least most if not all ffmpeg decoders and demuxers are fuzzed all the time and any found issue is addressed.