I am looking for an add-on which would me allow to download
embedded asf media
(without having Windows Media Player installed, or under Linux).
NOTE: The plugin DownloadHelper doesn't help ;)
Not a Firefox addon and not for Linux ... but i'm using SDP Downloader to 'grab' .asf and other video content. All you need is the URL (in FF you'll find it in Page Info/Media).
SDP Downloader is freeware.
Media Player Connectivity is a platform-independent add-on, which allows to open embedded movies with any media player.
Under Linux, to be able to capture the stream, I could use mencoder (that binary from MPlayer).