This is a frontend to youtube-dl I made that can download videos as a video, audio, or extract the autosubs and make them more human readable. You need a webserver with php and youtube-dl to make this work.
If you cannot install binaries on your system you can get the latest version of youtube-dl and "install" it in the same folder as this page and replace every instance of youtube-dl with ./youtube-dl
I added a script called install which will get most of the things you need to make this work. I made it for Debian 9 and can't help you if you aren't using that os