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Surprising to learn that H.264 owes most of its success, not to any
proprietary encoder implementations, but to one released under the GPL:
x264.

Here <http://x264dev.multimedia.cx/?p=164> one of x264’s developers explains
why the proprietary vendors get the encoding so wrong.

And from here <http://x264dev.multimedia.cx/?p=292>:

Youtube, Facebook, Hulu, and Vimeo all use ffmpeg and x264. Adobe’s
H.264 encoder in Flash Media Encoder is so utterly awful that it is far
worse than ffmpeg’s H.263 or Theora; they’re practically assuming users
will go use x264 instead.