I have a WebM Video with Vorbis audio. I load it into Avidemux, click "Save Audio" and it creates a dialog to save the file as filename.* under All Files
When I save it as filename.ogg as it is Vorbis audio, I get a file which cannot be played by my media player.
However if I run ffmpeg -i filename.webm -map 0:a -c:a copy filename.ogg I get a working file, with roughly the same filesize as the one produced by avidemux (153MB from ffmpeg vs 150MB from avidemux)
We cannot create Ogg containers yet, so no working Vorbis export. Patch welcome.