They are automatically converting all the HD video to 3D on their site. Swing by my desk if you want to borrow my 3D glasses to watch. They have a great example video about Parahawking in Nepal and give a high-level technical breakdown of how they’re doing it in the article.
How we’re making even more 3D video available on YouTube
Last year we kicked off a beta feature that let creators convert YouTube videos into 3D with a click, and since then you’ve converted hundreds of thousands of your videos to 3D. Today we’re expanding the beta to all of you by adding automatic 3D conversion for short-form videos uploaded in 1080p. Meaning, you can select 3D viewing in the Quality settings (click on the gear icon) on the YouTube player, then pop on your 3D glasses and see YouTube in another dimension.
– Randall Noval