MPEG-DASH and fragmented mp4

ffmpeg html5-video mp4 mpeg-dash
bhh1988 picture bhh1988 · Aug 12, 2013 · Viewed 17.8k times · Source

My understanding of fragmented mp4 is that it is a single file, but internally it is structured as fragments. Can someone explain to me how these fragments can be addressed in the .mpd file for DASH? The .mpd files that I've seen seem to address various segments with separate urls, but a fragmented mp4, I imagine, would have to be addressed by byte offsets into the same url. How does the browser then know what times correspond to what byte ranges?

Answer

RabitChang picture RabitChang · Aug 22, 2013

Here's a example mpd for MPEG DASH main profile. The mp4 file described by this mpd is a fragmented mp4. As you see :

<SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="868-347185"/>
<SegmentURL media="bunny_15s_200kbit/bunny_200kbit_dashNonSeg.mp4" mediaRange="347186-664464"/>

At <SegmentURL> element, the fragments can be addressed into the same url, and you can find byte offsets at @mediaRange attribute.

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