These are all old and orphaned packages that are encoding GUIs to ffmpeg. emoc http://aur.archlinux.org/packages.php?ID=34109 Doesn't work. Just sits there and does not actually convert any videos.
myencoder http://aur.archlinux.org/packages.php?ID=31640 Source does not pass the validity check. Upstream states, "MyEncoding development has been scaled back" on 2010-06-20. hypervideoconverter http://aur.archlinux.org/packages.php?ID=21735 Flagged out of date. Upstream not updated since 2008-11-17 and its settings appear not to be compatible with ffmpeg in repository.
