> It’s really simple

Have you ever written a stateless transcoder like this? Of course it can be done, but saying “you could simply encode those chunks” and “It’s really simple” is pretty misleading especially if you are changing frame rates or sample rates or audio codecs during the encoding process.

That said, if there is someone that could do this at scale it would be Facebook.

Also this would mess up ABR streaming at least for the first people to watch the video which would not really guarantee “the perfect encoding always”.