This uses ffmpeg under the hood and muxes the file into a .m4a file without transcoding. Basically keeping whatever compression youtube used for the audio (which is some sort of mpeg4 compatible audio, probably depends a little bit)
This still recompressed, but it's the best you can do using youtube as the source.
- uploader (almost certainly, but theoretically you could skip this step if you encoded your video well) compresses audio
- uploader uploads to youtube
- youtube re-compresses the audio again (almost certainly transcoding into a different codec)
I received a notification to use Door Dash yesterday, to order food... while I was cooking soup.