3GPP TSG-SA WG4 Meeting #135 - AVFOPS Permanent Document v2.0.0

Document Information

Source: Xiaomi (PD editor)
Title: AVFOPS Permanent Document v2.0.0
Version: 1.1.0
Meeting: SA4#135, February 2026, Goa, India
Agenda Item: 9.5
Document for: Agreement

Main Technical Contributions

1. Introduction and Scope

This permanent document consolidates all conformance-related material for video operation points (VOPS), gathering requirements, frameworks, and test content submitted to SA4 meetings. The document has evolved from VOPS work item to FS_AVFOPS study item.

2. Conformance Framework (Clause 4)

2.1 Sample Bitstream Platform Overview (4.1)

The platform architecture consists of:
- Database: Contains descriptions of available sample bitstreams
- Hosting server(s): Store submitted bitstreams
- Public portal: Enables external users to search and download bitstreams
- Bitstream validator: Validates compliance with TS 26.265 constraints prior to upload

The database is proposed as a git repository on web-based platforms (GitHub/GitLab) using JSON/markup files. Each bitstream links to TS numbers and profiles via URNs.

2.2 Bitstream Validator (4.2)

Repository location: https://forge.3gpp.org/rep/sa4/ts-26.265/conformance/bitstream-validator

Key capabilities:
- Validates bitstream compliance with video coding specifications and profiles
- Validates compliance with TS 26.265 bitstream constraints
- Uses reference decoder (JVET) for codec conformance checking
- Implements programmatic constraint validation via XML schema

Technical approach:
1. Parse input bitstream and generate XML dump of syntax elements
2. Express VOPS constraints as XML schema (XSD 1.1)
3. Validate XML bitstream description against constraint schemas

Usage workflow:

# Generate XML description
python -m sa4_bitstream_validator dump bitstream_path description.xml

# Validate against operation point schema
python -m sa4_bitstream_validator validate description.xml bitstream_rules/operation_point.xsd

Advantages:
- Codec-agnostic constraint expression
- No programming knowledge required for constraint definition
- Reusable bitstream descriptions for database

2.3 VOPS Operation Points as XML Schema (4.2.4)

Constraints defined using XSD 1.1 with xs:assert elements. Example schema provided for MV-HEVC stereo operation point (vops_3gpp-mv-hevc-stereo.xsd) includes validation of:
- VPS multi-layer parameters
- Layer set configuration
- Scalability mask and ScalabilityId constraints
- VUI-specific constraints for MV-HEVC
- three_dimensional_reference_displays_info SEI message parameters

3. Framework Development Status (4.6)

Comprehensive status tracking table provided covering:

3.1 3GPP Video Representation Formats (4.6.2)

• High-Definition: None implemented
• High Dynamic Range: None implemented
• Stereoscopic format: None implemented

3.2 Common Bitstream Constraints (4.6.3)

AVC Bitstreams:
- Motion-vector constraints: None implemented
- Rate constraints: None implemented

HEVC Bitstreams:
- Progressive constraints: Done
- VUI constraints: Work-in-progress (done but not tested with bitstreams)
- Frame-packing constraints: None implemented

Specific VUI constraint validations include:
- vui_parameters_present_flag = 1
- aspect_ratio_info_present_flag = 1
- video_signal_type_present_flag = 1 and colour_description_present_flag = 1
- video_full_range_flag = 0
- overscan_info_present_flag = 0
- chroma_loc_info_present_flag = 1

Note: Timing information constraints proposed for removal (marked as issues)

3.3 Decoding Capabilities (4.6.4)

Status for various decoder profiles:
- AVC decoders (FullHD, UHD, 8K): None implemented
- HEVC decoders (HD, FullHD, 8K): None implemented
- MV-HEVC-Main-Dual-layers-UHD420-Dec: Work-in-progress
- MV-HEVC-Ext-Dual-layers-UHD420-Dec: None implemented
- HEVC-Frame-Packed-Stereo-Dec: None implemented

3.4 Video Operation Points (4.6.5)

• AVC/HEVC HD/HDR/UHD operation points: None implemented
• HEVC Stereo operation point: None implemented
• 3GPP MV-HEVC Stereo Operation Point: Work-in-progress
• 3GPP MV-HEVC-Ext Stereo: None implemented

4. Key Changes in Version 1.1.0 (SA4#135)

Alignment with TS 26.265 V19.1.0:
- Validation of multi-layer parameters in VPS
- Validation of ScalabilityId constraint added
- Validation of VUI-specific constraints for MV-HEVC operation points
- Validation of three_dimensional_reference_displays_info SEI message

MV-HEVC Stereo Common Bitstream Requirements (6.3.6.2):

Implemented validations:
- vps_num_layer_sets_minus1 >= 1
- layer_id_included_flag[1][0] = 1 with at least one other layer included
- scalability_mask_flag[1] = 1
- ScalabilityId[1][1] = 1
- default_output_layer_idc = 0
- chroma_format_idc = 1
- aspect_ratio_idc = 1
- Colour primaries/transfer/matrix combinations for SDR HD or HDR
- three_dimensional_reference_displays_info SEI message presence and constraints:
- num_ref_displays_minus1 = 0
- left_view_id[0] and right_view_id[0] validation against view_id_val

5. Conformance Material (Clause 5)

5.1 HEVC Conformance Material

Source Content:
- Polytech Nantes database: 31 sequences, 1920x1080, 10-bit 4:2:2 YUV at 25 fps (availability issues noted)

Compressed Bitstreams:

1. JVET conformance bitstreams: MV-HEVC Extended 10 and Multiview Main 10 profile test streams
2. 2-view configurations
3. 1024x768 and 1920x1088 resolutions

4. Level 4, 30 fps, 300 frames

5. Hummingbird_Spatial (5.1.2.2): New submission

6. Two-layer stereo MV-HEVC bitstream
7. Layer 0: HEVC Main profile (left-eye view)
8. Layer 1: HEVC Multiview Main profile (right-eye view)
9. Includes three_dimensional_reference_displays_info SEI message
10. No frame packing used

Reference Software:
- HM reference software for HEVC
- HTM reference software for MV-HEVC and 3D-HEVC extensions

6. External References and Background

Annex A provides background on DASH-IF conformance suite approach, noting that existing tools (DASH-IF, GPAC/MP4Box) can parse NAL units and generate XML dumps but do not implement comprehensive video bitstream validation against 3GPP operation point constraints.

Summary

This document represents significant progress in establishing a comprehensive conformance framework for 3GPP video operation points. The main achievements include:

1. Architectural design for bitstream validation platform
2. Working implementation of XML-based validation tool for MV-HEVC stereo constraints
3. Detailed status tracking of all operation points and constraints
4. Initial conformance bitstreams including the new Hummingbird_Spatial sequence

The work-in-progress items focus primarily on MV-HEVC stereo operation points, with most AVC and single-layer HEVC operation points awaiting implementation.