Dynamic mpd support by client

[irajs]

DASH clients MAY support the presentation of [=dynamic MPDs=].

Don't we want all client support dynamic MPDs?

Suggested text
This document requires:
DASH clients SHALL support the presentation of [=dynamic MPDs=].

[sandersaares]

This is something of a philosophical question. Is DASH-IF guidelines a set of "things clients should support"? Some believe it to be so, e.g. to say that all clients must support AAC and H.264. Another viewpoint is that DASH-IF guidelines should be a description of how to implement things, without going too far into saying what features are to be implemented.

I am netural on which interpretation DASH-IF should pursue but given the recent trend toward moving away from defining codec interoperability and staying more on the structural level, I think DASH-IF guidelines in general are floating toward the latter interptetation - of leaving it up to implementors to decide what features to implement and just describing how to do it well.

Unless we plan to actively pursue feature profiles, we should not make this a hard requirement. Given the present course of DASH-IF activities and the topics that attention is in practice focused on, I consider it unlikely that we decide to go into defining feature profiles.