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Lack of support for preselecting a Service Operation Point #141

Closed samhurst closed 1 month ago

samhurst commented 3 months ago

Context

Problem description

The current client API specifications do not allow the invoker to preselect a Service Operation Point when it has a priori knowledge of this and doesn't (or can't) rely on this information being present in the Media Entry Point resource (e.g. MPD/ServiceDescription@id in a DASH MPD).

We are considering the case where the controlling application on the UE has some prior knowledge of what Service Operation Point to select. For example, a media streaming application that knows it is only subscribed to the HD stream and not the UHD stream. This prior knowledge could be hard-coded into the application or obtained via reference point M8.

Suggested solution

We recommend adding a single Service Operation Point reference as a parameter in these three places:

  1. An optional input parameter to the initialize method of the Media Access Function in clause 13.2.3.2 of TS 26.512 (reference point M7).
  2. An optional query parameter to the 3GPP Service URL in clause 12.4 of TS 26.512 (reference point M6).
    • Because the Service URL request is a generic application's only opportunity to interact with the Media Delivery System.
    • estimatedTransferVolume also needs to be passed in to support Background Data Transfer.
  3. A required input parameter to the createMediaDeliverySession() method in clause 11.2.2.1 of TS 26.510 (reference point M6).
    • This last change is not strictly necessary since it duplicates the functionality of the activatePolicy() method, but is a useful convenience that would align this method with the change to the 3GPP Service URL launch above.
ibouazizi commented 3 months ago

In the API clause 11.3, the serviceOperationPointReference parameter is exchanged as part of the activatePolicy method. Isn't this enough for the API? We can of course also add the parameter to the service URL.

rjb1000 commented 3 months ago

From an API design perspective, I think there is a reasonable argument to keep the input parameters of createMediaDeliverySession() aligned with those of the Service URL.

Although this appears to duplicate the input parameters of activatePolicy(), this method is also used the change the Service Operation Point during the course of a media delivery session.

rjb1000 commented 3 months ago

The basic motivation for selecting a Service Operation Point at the start of a media streaming session is captured in point 5 of cause 4.0.6 in TS 26.501. It covers the case where the Service Operation Point is signalled in the Media Entry Point and the case where it is not, but it is (intentionally) unspecific about the details of how the selection is achieved.

@haudiobe's call flow in clause 5.7.6 of TS 26.501 only covers the case where the application chooses a Service Operation Point from the set advertised as Service Descriptions in the DASH MPD. There is no call flow corresponding to the case where an application has a priori knowledge of the Service Operation Point.

For this meeting cycle, we can at least add the missing parameter to the Service URL, which seems broadly agreeable.

We can also pass an Estimated data transfer volume parameter in the Service URL to support the initiation of a Background Data Transfer via a Service URL.

rjb1000 commented 3 months ago

TDocs reserved for SA4#129-e meeting:

Drafts shared with @haudiobe, @ibouazizi and @samhurst.

rjb1000 commented 2 months ago

Change Requests agreed at SA4#129-e meeting:

These go to SA#105 for approval.

rjb1000 commented 1 month ago

Change Requests approved at SA#105 (Melbourne):

rjb1000 commented 1 month ago

New specifications published: