Summary of S4-260226: Media Configuration for Avatar Calls

Introduction

This discussion paper addresses media configuration requirements for AR-MTSI clients supporting Avatar communication within the context of the Study on Avatar communication Phase 2. The Phase 2 study focuses on enabling additional Avatar use cases and enhancing Avatar-based RTC services with emphasis on quality of experience and advanced animation features for photo-realistic and immersive user experiences.

Background on Existing AR-MTSI Media Configuration

Current AR Support Parameters (TS 26.264 Clause 7)

The document reviews existing media configuration requirements defined in TS 26.264 for AR-MTSI clients:

• +sip.3gpp-ar-support parameter in SIP REGISTER Contact header with two values:
• "ar-capable": Terminal fully capable of receiving and rendering AR media
• "ar-assisted": Terminal capable of transmitting AR metadata on uplink but requires network rendering support (no support for processing/rendering 3D scenes)

Current Avatar Support Parameters (TS 26.264 Clause 7.3.1)

• +sip.3gpp-avatar-support parameter in SIP REGISTER Contact header with two values:
• "avatar-capable": Terminal fully capable of receiving, animating and rendering avatars
• "avatar-assisted": Terminal requires network support for avatar animation and rendering

Network-Assisted Avatar Rendering (TS 26.264 Clause 7.3.2)

When network animation and rendering is requested, an AR AS shall:
- Allocate an MF capable of real-time avatar rendering
- Configure the MF with appropriate rendering parameters based on receiving UE's video capabilities
- Modify SDP to route avatar animation data to the MF instead of receiving UE, inserting the MF into the media path

Identified Gap

The document identifies a critical gap: TS 26.264 has not yet documented the media configuration details for an AR-MTSI client in terminal that intends to participate in an avatar call.

When media configuration details were proposed in S4-251845 at SA4-134 Dallas meeting, feedback indicated that the behavior of IMS network elements is unspecified in the IMS architecture when an MTSI client sends the new Contact header field parameters "+sip.3gpp-ar-support" and/or "+sip.3gpp-avatar-support" in a SIP REGISTER message.

Proposal

The document proposes to send a Liaison Statement to SA2 requesting:
- Definition of IMS network behavior when an AR-MTSI client registers with Contact header field "+sip.3gpp-ar-support" and/or "+sip.3gpp-avatar-support"
- Specification of how to provide a suitable MF capable of providing AR rendering and/or avatar rendering support in an IMS session

A draft LS is provided in companion document S4-260227.