>>106830905
With media.cache_readahead_limit
and media.cache_resume_threshold
- they don't work with DASH streams tho so it might not work. Other useful flags are listed in betterfox's fastfox config on github.
However, for a lot of sites that use a custom (often crappy) player, the FastStream Video Player often works pretty well: https://addons.mozilla.org/en-US/firefox/addon/faststream/
You can of course use cat-catch to download the stream too