I have fragmented mp4 which I want to send users through HLS. It's ok if I just send it as is. But I need opportunity to reorder fragments in this video.
For example initial video, which looks like this: original video format
I want reorganize fragments and get this: expected video format
I try make it locally, and it's work in VLS player (HLS). For this I modified sequence number for fragments in moof (mfhd). But when I try play it remotely (HLS) it does not work. I think, that some players (js) expect some additional information from each fragment, probably for example time offset. But I can not find which atom (box) contain this information. I spent a lot of time searching and I'm still at the very beginning of the problem.
I tried to modify the fragment sequence number, but it doesn't work.
The "Track Fragment Media Decode Time Box" (tfdt) stores the baseMediaDecodeTime which is the accumulative decode time.
Consider the following...
baseMediaDecodeTime must increase monotonically for each chunk.
This means you must update (replace) the tfdt entry of chunk with expected next tftd entry.
When you naively reorder the chunks, the baseMediaDecodeTime will be invalid.
The "Track Fragment Media Decode Time Box" (tfdt) is located inside each moof header at:
moof --> traf --> tfdt