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DASH profile for CMAF: is CMAF fragment mapped to DASH segment or DASH subsegment? Should it be CMAF segment instead? #392

Open sandersaares opened 4 years ago

sandersaares commented 4 years ago

The DASH profile for CMAF equates DASH segments to CMAF fragments:

If @startsWithSAP is present and has value of 1 or 2, then every DASH Segment shall conform to a CMAF Fragment.

But some DASH presentations only consist of 1 single DASH segment that is made of multiple DASH subsegments. Surely in this case it should be that a CMAF fragment is a DASH subsegment?

CMAF defines a CMAF segment roughly as an addressable list of one or more CMAF fragments. As DASH (sub)segments are all addressable, shouldn't the equality be with CMAF segment instead of CMAF fragment?

There seems to be some confusion in the terminology here. Likely the DASH distinction between segment and subsegment is a contributor to the confusion. I propose that DASH-IF suggest to MPEG to get rid of the term subsegment and reference each addressable unit as a DASH segment, regardless of whether it is a byte range or not.