Multiple KIDs

[wilaw]

[From https://github.com/Dash-Industry-Forum/dash.js/issues/3343]

What would be the use case for sending multiple KIDs at once? If an AdaptationSet contains different keys/kids for different representations is the client supposed to embed this in one single license request?

[lpiron]

We are currently working in DASH-IF on this use case of several content keys in an Adaptation Set (see Dash-Industry-Forum/DASH-IF-IOP#400). The license request model defined in the Security Guidelines will most probably be updated accordingly.
Note that, from my understanding, in a DRM per DRM case, the license requests may be different. For example, a Widevine license server can provide licenses not requested because some business logic associates a KID to a contentID, hence asking a license for a KID means the content is requested, and additional licenses can be delivered in the answer (this reduces the number of license requests). Other DRMs may allow having several KID in a request, even if these are not in the same Adaptation Set. This is a DRM provider decision.

[ZmGorynych]

How would we prevent a situation when the client attempts to shift into a representation it cannot decrypt?
We need some signaling in the MPD to prevent such a switch.