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VP9 Video Codec Support Implementation Plan

Overview

Add VP9 video codec support to Muxide, complementing the existing AV1 support. VP9 is a royalty-free video codec developed by Google, commonly used in WebM containers and supported by major browsers.

Current State Analysis

  • ✅ AV1 support exists (OBU format parsing)
  • ✅ H.264/H.265 support exists (Annex B format)
  • ✅ MP4 container structure established
  • ✅ Codec abstraction pattern established

VP9 Technical Requirements

VP9 Frame Format

VP9 uses IVF (Intra Video Frame) containers for storage, but for MP4 muxing we need:

  • Compressed VP9 frames (similar to AV1 OBUs but different structure)
  • Frame headers containing temporal and spatial information
  • Key frame detection for sync samples
  • Resolution extraction from sequence headers

VP9 Bitstream Structure

VP9 Frame:
├── Frame Header (variable length)
│   ├── Frame Marker (2 bytes: 0x49, 0x83, 0x42)
│   ├── Profile (2 bits)
│   ├── Show Existing Frame (1 bit)
│   ├── Frame Type (1 bit: 0=key, 1=inter)
│   ├── Show Frame (1 bit)
│   ├── Error Resilient (1 bit)
│   └── ... (additional header fields)
├── Compressed Data (variable length)
└── Optional: Frame Size (4 bytes)

Implementation Scope

Phase 1: Core VP9 Parsing

  • VP9 frame header parsing
  • Key frame detection
  • Resolution extraction from sequence parameters
  • Basic frame validation

Phase 2: MP4 Integration

  • VP9 codec configuration box (vpcC)
  • Sample entry creation
  • Frame data extraction and writing
  • Sync sample detection

Phase 3: Testing & Validation

  • Unit tests with VP9 fixtures
  • Integration tests
  • FFmpeg compatibility verification
  • Performance benchmarking

Files to Modify

Core Implementation

  • src/codec/mod.rs - Add VP9 module
  • src/codec/vp9.rs - New VP9 codec implementation
  • src/api.rs - Add VideoCodec::Vp9 variant
  • src/muxer/mp4.rs - Integrate VP9 codec handling

Testing

  • tests/ - Add VP9 test fixtures
  • tests/vp9_muxing.rs - VP9-specific tests

Dependencies

  • No new external dependencies (maintain zero-dependency goal)
  • Use existing bit manipulation utilities

Success Criteria

  • VP9 video files mux correctly into MP4
  • FFmpeg can play resulting MP4 files
  • Performance comparable to other codecs
  • Comprehensive test coverage
  • Documentation updated

Risk Assessment

  • Low Risk: Similar to AV1 implementation pattern
  • Medium Complexity: VP9 headers more complex than H.264 but similar to AV1
  • Testing: Need VP9 sample data (can generate with ffmpeg)

Timeline Estimate

  • Phase 1: 2-3 days (parsing logic)
  • Phase 2: 1-2 days (MP4 integration)
  • Phase 3: 1-2 days (testing & validation)
  • Total: 4-7 days

Next Steps

  1. Research VP9 bitstream specification
  2. Obtain/create VP9 test fixtures
  3. Implement basic frame parsing
  4. Integrate with MP4 muxer
  5. Test and validate c:\Users\micha\repos\muxide\VP9_IMPLEMENTATION_PLAN.md