# 3GPP SA4 LS on Compression Aspects of MPEG-I ARF (ISO/IEC DIS 23090-39)

## Document Overview

This is a Liaison Statement (LS) from 3GPP TSG SA WG4 to ISO/IEC JTC1/SC29/WG7 and WG3 regarding compression aspects of avatar representation formats for Release 20 work on avatar communication Phase 2.

## Background Context

### Release 19 Baseline
- 3GPP SA4 has adopted **ISO/IEC DIS 23090-39 (MPEG-I: Avatar Representation Formats)** as the representation format for user avatars in avatar communication over IMS
- This adoption is specified in **TS 26.264** for Release 19
- **Limitation identified**: Compression aspects of avatar data were not addressed in Release 19 because ISO/IEC DIS 23090-39 does not yet specify compression mechanisms

### Release 20 Phase 2 Study
- SA4 has initiated a **Phase 2 study on avatar communication** in Release 20
- **Key objective**: Compression of static avatar data and animation data
- **Study conclusion timeline**: SA4#137e meeting (August 24-28, 2026)
- **Normative work completion**: March 2027

## Technical Questions to ISO/IEC

SA4 is seeking clarification on two critical aspects:

### Question 1: Existing MPEG Compression Technologies
Are there existing MPEG technologies that can be utilized to compress:
- **Avatar static data** (especially meshes)
- **Avatar animation data** including:
  - Blend shape sets
  - Skeletal animation
  - Other animation-related information

### Question 2: Integration Timeline
If such compression technologies exist:
- Are there plans to integrate them into ISO/IEC DIS 23090-39?
- What is the anticipated timeline for such integration in the context of 3GPP Release 20 schedule?

## Requested Action

SA4 formally requests ISO/IEC SC29/WG7 and ISO/IEC SC29/WG3 to provide answers to both questions above, considering the Release 20 timeline constraints.