A.1 Introduction

26.1413GPPIP Multimedia System (IMS) Messaging and PresenceMedia formats and codecsRelease 17TS

The Combination of CS and IMS services (CSI) is an operation mode combining circuit switch calls and IMS services, where the UE presents the CS and IMS services within one context to the user [59][60]. However, the capabilitiy to simultaneously render certain media types of a CS call and IMS session may be limited by a UE and capability exchange alone may not be enough to resolve such conflicts. For instance:

– During a CS speech call, a UE may not be able to render additional speech accompanying a video clip in an IMS session. This limitation is not clear if the UE has indicated that it is capable of receiving video clips.

– During a CS multimedia call, a UE may not be able to both display video from the CS call and images from the IMS session. Although the UE is not capable to fully render images and video simultaneously, it may be possible to view images in front of video.

The above conflicts are resolved by applying default rules specified in [59]. This Annex describes the UE behaviour for a number of scenarios drawn from the rules in [59]. This list may be extended in future versions of this specification.

Note that the IMS media types and formats applicable to CSI are specified in:

– clauses 6 and 9 of reference [61] for streamed media;

– clauses 4 and 5 of the present document for media delivered in messages.