There’s also an open-source utility for the job that I’ve been using constantly: Pandoc. Pandoc calls itself "a universal document converter," with support for dozens of markup formats and document ...
To turn a video into an audio file on your iPhone, you'll need to download a third-party app from the App Store.
Discover Vert, the open-source file converter that offers fast, secure, and universal conversion for all your digital assets.