First we need to install ffmpeg and add a bunch of codecs
brew install ffmpeg --with-libass --with-openssl --with-libvorbis --with-libvpx --with-theora
Converting mp4 => ogv
ffmpeg -i input.mp4 -q:v 10 -c:v libtheora -c:a libvorbis output.ogv
Converting mp4 => webm
ffmpeg -i input.mp4 -q:v 10 -c:v libvpx -c:a libvorbis output.webm
did you try free hd video converter factory? A free tool for converting videos. I am using it to convert video easily, maybe you should try too!