# 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-view configurations
   - 1024x768 and 1920x1088 resolutions
   - Level 4, 30 fps, 300 frames

2. **Hummingbird_Spatial** (5.1.2.2): New submission
   - Two-layer stereo MV-HEVC bitstream
   - Layer 0: HEVC Main profile (left-eye view)
   - Layer 1: HEVC Multiview Main profile (right-eye view)
   - Includes three_dimensional_reference_displays_info SEI message
   - 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.