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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.

Nick
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1 Answers1

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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
VC.One
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Markus Schumann
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