nalcore

nalcore is a Rust project for software decoding of H.264/AVC and H.265/HEVC bitstreams.

Goal

Build a clean, correct, and maintainable decoder foundation first, then optimize for performance once the decode pipeline is stable.

Initial Scope

• Bitstream parsing and NAL unit handling
• Sequence and picture parameter set parsing
• Slice parsing and decode pipeline plumbing
• Software decode to planar frame output
• Regression tests against small reference streams

Non-Goals for the First Pass

• Container demuxing
• Hardware acceleration
• Aggressive SIMD optimization
• Broad codec support beyond H.264 and H.265

Working Principles

• Correctness before speed
• Small, explicit Rust abstractions
• Minimal unsafe
• Deterministic tests and fixtures

Early Milestones

1. Build the bit reader and common parsing utilities.
2. Implement H.264 baseline parsing and decode flow.
3. Add H.265 parsing and decode flow.
4. Add conformance-oriented regression tests.
5. Profile and optimize the hot paths.

Status

Project bootstrap in progress.

Planning

See Longer-Term Plans for tentative architecture, decoding, testing, safety, tooling, and release ideas beyond the currently tracked GitHub issues.