There are number of different places to get this info. I use Termux with yt-dlp and decode to MP4 or extract audio only which requires ffmpeg and it works fine if a little slow. I decoded a 300 GB twitch stream that after downloading took about 20 mins to complete the decode (encode?) to mp4 on my Pixel6. But it works perfectly.

e.g see https://gist.github.com/cyrillkuettel/d63785cf5f4c00106ae215... for example.