# 3GPP Technical Document Summary: CR 0003 Rev 1 for TS 26.813 (Avatar Services)

## Document Overview
This is a Category F (correction) Change Request for TS 26.813 Release 19, version 19.1.0, addressing editorial corrections and reference updates across multiple sections of the Avatar specification.

## Main Technical Contributions

### Section 2: References Updates
- **Corrected normative and informative references** including:
  - Updated 3GPP TR 22.856 to V19.2.0 (Localized Mobile Metaverse Services)
  - Updated 3GPP TS 23.228 to V19.2.0 (IMS Stage 2)
  - Corrected formatting and accessibility information for external references (AFLW, LFPW, WFLW datasets)
  - Added new reference [34] for I.-J. Hirsh and C. E. Sherrick study on perceived order in different sense modalities
  - Added new reference [35] for Hyojin Park et al. study on lip movements and brain oscillations

### Section 5: Use Cases and Potential Requirements

#### UC1: Avatar Communication
**Editorial corrections:**
- Removed duplicate requirement regarding bidirectional transitioning between video and avatar media
- Clarified voice-driven avatar animation requirements
- Enhanced description of audio-visual synchronization for accessibility

**Key technical aspects maintained:**
- Real-time facial expression and body movement metadata extraction based on ASR/NLP
- Voice-driven 2D/3D avatar animation generation and encoding/decoding
- Avatar sharing, modification, and real-time composing capabilities
- Lip movement synchronization for enhanced intelligibility in noisy environments

#### UC2: Multi-party Shared Experiences
**Corrections:**
- Refined description of collaborative working scenarios
- Added specific use case for classroom environments with differential avatar expression control
- Added teenage social gathering scenario with selective expression filtering

**Technical requirements:**
- Secure end-to-end avatar expression delivery for specific audiences
- Network-based capability for filtering/replacing avatar expressions for selected audiences
- Support for filtering or replacing selected subsets of face and body expressions during avatar animation generation

#### UC3: Multi-user Gaming
**Editorial improvements:**
- Clarified synchronization requirements between different modalities
- Updated KPI requirements with proper formatting

**Key synchronization thresholds maintained:**
- Audio-tactile: 12ms (audio first), 25ms (tactile first)
- Visual-tactile: 30ms (video first), 20ms (tactile first)  
- Audio-visual: 20ms (audio first), 20ms (video first)

**KPI requirements:**
- End-to-end latency: 5-20ms
- Service bit rate: 1-1000 Mbit/s
- Positioning accuracy: <1m

#### UC4: Avatar Generation, Storage, and Access
**Corrections:**
- Reformatted requirements section for clarity
- Consolidated requirements from TR 22.856
- Enhanced description of avatar lifecycle management

**Technical requirements:**
- Avatar generation, update, and animation support (UE and/or network-based)
- Avatar metadata for parental control and access management
- Discovery and negotiation of network functions for avatar processing
- Upload, storage, search, transmission, and update capabilities
- Avatar identification and mapping to subscribers
- Authorization and usage rights management

#### UC5: AI-Based Avatar
**Editorial updates:**
- Clarified autonomous virtual alter ego concept
- Enhanced description of AI avatar capabilities

**Technical requirements:**
- AI/ML model transfer per TR 23.700-80 framework
- Secure registration, storage, and updating of AI-based avatars
- Third-party authentication assistance for avatar usage
- Network storage for application-specific user data
- Multi-modal instruction transmission for real-time interaction
- Charging information collection for avatar-associated communications

### Section 6.3.4: MPEG Avatar Representation Format
**Corrections:**
- Updated reference to ISO/IEC 23090-39 (ARF specification)
- Clarified ARF data model components
- Enhanced description of ARF container formats

**Technical content maintained:**
- ARF data model including skeletons, meshes, blendshapes, skins, landmarks, and nodes
- Support for ISOBMFF and Zip-based containers
- Integration with MPEG Scene Description (ISO/IEC 23090-14)
- Reference client architecture with Avatar pipeline in Media Access Function
- Ongoing exploration experiments for compression, geometry integration, animation formats, content discovery, and animation controllers

### Section 7.1: General Architecture and Call Flows
**Corrections:**
- Removed leftover editorial brackets in text
- Clarified avatar function descriptions

**Key architectural components:**
- **Avatar Storage**: Base avatar storage with access control and authorization
- **Avatar Animation**: Retrieves base avatar and performs animation using format-specific data streams
- **Scene Management**: Creates and composes shared 3D scenes with avatar integration
- **Animation Data Generation**: Converts raw signals (camera, microphone, sensors) to animation data
- **Base Avatar Generation**: Creates base avatar from captured inputs

**Workflow distribution:**
- Multiple workflow examples showing different distributions of avatar functions between sending UE, network, and receiving UE
- Workflow selection depends on service requirements, UE capabilities, and network configuration

## Impact Assessment
The CR addresses editorial errors and incorrect references that would otherwise remain in the specification. No functional changes are introduced, only corrections and clarifications to existing content.