There is a problem with the ffmpeg link on the rock installing page…the file is no longer being maintained there.
For years I’ve been hosting FFmpeg static builds to make it easy for people to use this great software. Offering the latest stable release for five architectures as well as development versions for those that want the latest features. However, my free time to maintain the builds has dwindled, so I decided to start a Patreon page where users can pledge a few bucks a month to support my efforts if they deem it worthwhile. If enough people think so, I’ll get back to it.
John Van Sickle