I use Ubuntu as my main desktop both at work and at home, and chromium as my default browser. For ages it’s been annoying me that some videos on youtube don’t play. Well, I’ve finally gotten around to fixing it.
It seems mp4 playback is missing from chromium on ubuntu, and can be added with:
sudo apt-get install chromium-codecs-ffmpeg-extra
Restart chromium and you can go back to watching kittens falling off tables.