More refined subtitle support (better timing, more flexibility in how they are presented and better timing) Complex chapter structure (think dvd menus and “bandersnatch” interactive movies and probably things nobody has thougth of doing because of lacks in the technology), segment linking (linking to a file and a timestamp, so you can reuse sections such as intros etc…) Arbitrary file support, to embed anything, text documents, subtitle font files, cover images, license information, client side storage High precision timestamps, rich metadata

One great thing is it can be extended, so it’s future proof, one bad thing is, it can be extended, so of course Apple made extensions that only work on their shit