[mmcclure]

Yep, you make a really good point, thanks for the feedback. I think this bit would probably make sense to live in the upcoming "processing" section.

If anyone's interested, this is called the moov atom, and when you use "web playback" presets in tools like Handbrake, that's typically what it does is move that header to the beginning of the file. The progressive playback issues for files not optimized has improved somewhat when the file's host supports range requests, since browsers have gotten smart enough to try and check the end of the file for that header via range requests.

If you're interested in more along the codec/container line, one of my colleagues gave a talk on the internals of MP4 containers at Demuxed a few years ago[0] and another gave a Streaming Media keynote on the history of codecs and containers, particularly as they relate to online video[1].

[0] https://www.youtube.com/watch?v=iJAPTY3B7yE [1] https://www.youtube.com/watch?v=9Qo3WfsK4vc