Handy website which converts audio to other audio, video to audio, other formats: cloudconvert.com
https://cloudconvert.com/It is free to use, at first. If you do a LOT of converting (in my case, from mpg and mp4 and mkv, etc to mp3), they ask you to set up a free account. If you keep using it, they ask you to pay. You get 500 minutes of conversion time for $9. Not bad, to me, if you need to convert a lot.
hunter
(38,930 posts)The default conversions work well enough and there's extremely fine control if you need it.
https://ffmpeg.org/
The handbrake video transcoder is built on that, for anyone who'd rather not use command line tools.
https://handbrake.fr/
A cloud based solution might be handy for a phone or tablet.
CloudWatcher
(1,923 posts)The only problem with ffmpeg is that it is so powerful there are 1001 different options and browsing through the documentation can seem like getting a PhD in audio/video engineering. And a lot of people are turned off by a command-line interface
But ... I'd be willing to wager that all of the audio/video processing on cloudconvert.com is running ffmpeg to do the actual work.
So ... if audio/video processing is something you do routinely, take the time to get ffmpeg and run it locally on your computer. It'll wind up being a lot faster than waiting for the uploads/downloads to any site in the cloud.