cmff and cmfs assumptions in section 4

[sdp198]

Towards the end of section 4 there is this text: If the Segment Type Box(styp)is present and contains:

• 'cmff': an CMAF media segment as defined in this specification mustconform to a CMAF Fragment (as defined in CMAF Spec)
• 'cmfs': an CMAF media segment as defined in this specification mustconform to a CMAF Segment (as defined in CMAF Spec)

These statements aren't necessarily correct. Those brands can be used on the first chunk of a CMAF Fragment and first chunk of a CMAF Segment respectively.

As the "CMAF Byte Stream Media Segment " is defined in this document to be a single CMAF Chunk then a CMAF Segment or CMAF Fragment consisting of multiple CMAF Chunks will necessarily be multiple CMAF Byte Stream Media Segments for the purposes of this spec. If those brands are applied in the manner permitted by CMAF then the "must" here will not be satisfied.

I think this text can be safely removed, as the user agent does not need to know about Fragment or Segment boundaries. However if it is desired to say something then two things are needed:

• To indicate that the brand indicates the start of a series of one or more "CMAF Byte Stream Media Segment"s which conform to the requirements of a CMAF Fragment/Segment
• The wording "CMAF media segment as defined in this specification" needs to be changed to "CMAF Byte Stream Media Segment" since taht is actually what is defined in this specification.

[haudiobe]

AHG 2020/11/19: Propose to remove - agreed.

[haudiobe]

Implemented: https://1drv.ms/w/s!AiNJEPgowJnWgqsz3EFQvnMD7BhN0w?e=42BwJJ