Ant website support hand some helpful information about installing AVD-NativeApp which I downloaded from their archive page.
This app needs to be installed separately due to being removed from newer F/F releases. Once installed downloads worked fine even on another couple of video down loaders I use!

не работает!

it is not working to download a video even though the video is playing fine on the screen

Limited functionality, so I use udl helper now

Used to be a decent Downloader for most sites, but now you can't find the Native App on any of the file sharing sites listed anymore, so it's not much good anymore.

Most flawless working video downloader that I tried (and I tried all of the recently most popular in Firefox addons). The only problem was with finding and downloading the Native app (go to their homepage - ant.com). It won't appear automaticly as a shortcut (just click your extensions list), so it's maybe too complicated for some people. But it works perfectly.

It's dead.

Doesn't work unless you download something on your computer