>>58432
Regarding those. All videos are x265 encoded streams in qt containers.
Except in this case: >>58269
The uploaded files had .mp4 extension and the stored have .mp4
While in this case: >>58431
The uploaded files had .mp4 extension and the stored have .qt
All play for me in browser.
I think a lot depends on what device/OS and browser are used by the uploader.
For example Dela wrote some script that could tell iOS from various characteristics of posts, he went on scaring users on agatha2 at least on one occasion with it.