Codec

Theora

Ogg/Theora? serve a particular purpose; they have no royalties. Both H.264 and AAC have royalties, even if most people don't pay them.

Wikipedia, for example, one of the top 10 most popular websites in the world, uses Ogg and Theora exclusively, and as the web moves towards more rich media, they will stick with that simply for legal reasons.

Container

mkv

mp4

Yamb

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