It's nice of them that his video is a webm, while the others are mp4s. E.g. try ...

spacefight · on Jan 3, 2015

s/is/is only/

And yes, the mp4 version is not just not linked, it's simply not there: http://c3media.vsos.ethz.ch/congress/2014/h264-hd/

teamhappy · on Jan 3, 2015

All talks are available in WebM. Try inspecting the download button.

aselzer · on Jan 3, 2015

When clicking on the download button on his video, there is only a webm video and an opus sound file.

For all the other talks there are also mp4 videos and mp3 audio files.

chippy · on Jan 3, 2015