H.264 Annex B Parser

A Rust library for parsing H.264 Annex B bitstreams. This library provides zero-copy parsing of NAL units, parameter sets (SPS/PPS), slice headers, and access unit assembly.

Features

• Annex B parsing: Handles start codes (0x000001 and 0x00000001)
• NAL unit parsing: Extracts and processes Network Abstraction Layer units
• Parameter sets: Decodes SPS (Sequence Parameter Set) and PPS (Picture Parameter Set)
• Access Units: Groups NAL units into frames/pictures
• Keyframe detection: Identifies IDR frames and recovery points
• SEI parsing: Basic support for Supplemental Enhancement Information
• Streaming support: Handles chunked input data
• Zero-copy design: Minimizes memory allocations where possible

Usage

Add to your Cargo.toml:

[dependencies]
h264-parser = "0.1.0"

Basic example:

use h264_parser::AnnexBParser;
use std::fs::File;
use std::io::Read;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut file = File::open("video.h264")?;
    let mut buffer = Vec::new();
    file.read_to_end(&mut buffer)?;

    let mut parser = AnnexBParser::new();
    parser.push(&buffer);

    while let Ok(Some(au)) = parser.next_access_unit() {
        println!("Frame: keyframe={}", au.is_keyframe());
        
        if let Some(ref sps) = au.sps {
            println!("  Resolution: {}x{}", sps.width, sps.height);
        }
        
        for nal in au.nals() {
            println!("  NAL: {:?}", nal.nal_type);
        }
    }

    Ok(())
}

Architecture

The library is organized into the following modules:

• bytescan: Start code detection and NAL unit tokenization
• nal: NAL header parsing and EBSP/RBSP conversion
• bitreader: Bit-level reading utilities
• eg: Exp-Golomb encoding/decoding
• sps: Sequence Parameter Set parsing
• pps: Picture Parameter Set parsing
• sei: SEI message parsing
• slice: Slice header parsing
• au: Access Unit assembly
• parser: Main parser facade

Supported NAL Unit Types

• Non-IDR slices (P/B frames)
• IDR slices (I frames)
• SPS (Sequence Parameter Set)
• PPS (Picture Parameter Set)
• SEI (Supplemental Enhancement Information)
• AUD (Access Unit Delimiter)
• End of sequence/stream markers

Limitations

This is a parsing-only library that:

• Does not perform full H.264 decoding
• Does not manage DPB (Decoded Picture Buffer)
• Does not handle RTP packetization
• Does not provide muxing/demuxing capabilities