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> The problem is that html5 video doesn't work everywhere (we actually encode six different videos to cover the most browsers)

Six different videos?? Anyone knows more about html5 video fragmentation and why six videos are required?

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They offer the ability to playback in reverse, so I imagine it's three different formats, doubled so that there's a reverse copy of each video.

If I had to guess, they're probably encoding MP4/H.264, WebM/VP8, and Ogg/Theora.

So close:

> Note that there are 6 separate encodings -- mp4, webm, and reduced mp4, for forward and reverse

That makes sense - looks like WebM/VP8 support in browsers is a superset of Ogg/Theora support [1]. It would be silly to serve up Ogg/Theora unless it yielded better quality/bitrate (and I'm not up-to-date on how those two compare in quality at the same bitrate).

[1] http://beta.caniuse.com/#search=video

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