Convert ogv HTML5 Video
Searching for the best way to convert high quality ogv videos to use with Mozilla Browsers, I realized that most converters produce crappy quality. This was the case for VLC and Miro Video Converter. Most converters you can download for free are just an UI for ffmpeg. But it is sometimes tricky to find good settings for the conversion. Gladly I found this on stack exchange after some digging:
ffmpeg -i input -vcodec libtheora -qscale 6 -acodec libvorbis -aq 5 output.ogv
You can change the -qscale property from one to ten to adjust the quality and it works good.