Sometimes when using winff (via ffmpeg) http://winff.org/html_new/ to convert mp3s to ogg you get an annoying error message – Unknown encoder ‘vorbis’.
To solve this problem try the following.
Open up winff, and from the main menu select Edit->Presets. Select Audio type (not a video we are converting), and OGG sub category. In preset command line parameters replace -acodec vorbis with instead -acodec libvorbis (note lib in libvorbis). Then CLICK ADD/UPDATE BUTTON (important, it won’t work making preset changes if you just save it), then press Save Button.
(click for larger image)
Works for me under linux.