Rust rewrite of FFmpeg, verified against FFmpeg's output bit-for-bit.

This codebase is AI-generated. Written by Claude (Anthropic) via Claude Code, directed and reviewed by a human. The AI reads FFmpeg's C source and reimplements it in Rust. Every conformance claim below is verified by automated CI on every commit, comparing to FFmpeg's output.

The intention of this project is to push the boundaries of what is possible with AI rewriting codebases in Rust. It provides no additional features compared to FFmpeg, and despite incorporating FFmpeg's assembly code, is significantly slower.

Status

Component Conformance Notes

H.264 decode 79/79 BITEXACT CAVLC + CABAC, Baseline through High profile

H.264 FRext 23/55 bitexact Progressive 4:2:0 8-bit done; MBAFF/PAFF/10-bit remaining

H.264 NEON (aarch64) 1.75x speedup MC, IDCT, deblock — FFmpeg's vendored assembly via cc

WAV demuxer + PCM bitexact RIFF/RIFX/RF64/BW64, 17 PCM formats, 13/13 FATE files

WAV muxer bitexact Roundtrip verified

FLAC, WavPack bitexact Via symphonia adapter

Vorbis, AAC, MP3 ~120-140 dB SNR Lossy codecs, float precision only

AV1 bitexact Via rav1d adapter

MP4 demuxer working H.264, AV1, AAC tracks

Video player 24fps 0-drop GPU (wgpu), ffplay-style A/V sync, pause, volume

H.264 decoder

The H.264 decoder is ~30K lines of Rust across 25 modules. It implements:

• CAVLC and CABAC entropy coding

• All intra prediction modes (4x4, 8x8, 16x16, chroma)

• Quarter-pel motion compensation (6-tap FIR luma, bilinear chroma)

• 4x4 and 8x8 IDCT with Hadamard DC transforms

• In-loop deblocking filter

• MMCO and sliding-window reference management

• Weighted prediction (uni/bi)

• B-frames with direct prediction (spatial + temporal)

• High profile: 8x8 transforms, custom scaling matrices

• MBAFF interlaced (partial — field/frame MB switching, CABAC context adaptation)

• Frame-level threading with wavefront deblocking

• aarch64 NEON assembly for MC, IDCT, and deblocking (feature-gated)

Architecture details: H264.md. Known FFmpeg behavioral differences: DIVERGENCES.md.

Not yet implemented

FFmpeg has hundreds of codecs and formats. wedeo currently covers a small subset. Major gaps for parity:

• Video codecs — VP9, HEVC/H.265, MPEG-2, MPEG-4 Part 2, VP8, Theora. H.264 is missing interlaced (MBAFF/PAFF), 10-bit, and 4:2:2/4:4:4.

• Video encoding — no encoders exist yet (H.264, H.265, AV1 via rav1e)

• Muxers — only WAV. No MP4/MOV, MKV/WebM, or MPEG-TS muxer.

• Demuxers — no MKV/WebM, MPEG-TS, FLV, or AVI demuxer (MP4 and WAV only, plus symphonia-backed formats)

• Filters — trait skeleton exists but no functional filter graph (no scale, crop, overlay, fps, etc.)

• Player — no seek, no subtitle rendering, no hardware-accelerated decode

• Infrastructure — no interruptible I/O (network streams), no chapter/program support, no avformat_find_stream_info equivalent

Quick start

Install the CLI

# From source (includes AV1 support via rav1d) cargo install --git https://github.com/sharifhsn/wedeo wedeo-cli

# From source (includes AV1 support via rav1d) cargo install --git https://github.com/sharifhsn/wedeo wedeo-cli

Play a video

# Also from source — AV1, H.264, and audio all work cargo install --git https://github.com/sharifhsn/wedeo wedeo-play wedeo-play video.mp4

# Also from source — AV1, H.264, and audio all work cargo install --git https://github.com/sharifhsn/wedeo wedeo-play wedeo-play video.mp4

Use as a library

# Cargo.toml — core crates are on crates.io [dependencies] wedeo = "0.1.2" wedeo-codec-h264 = "0.1.2" # H.264 decoder wedeo-format-mp4 = "0.1.2" # MP4 demuxer wedeo-symphonia = "0.1.2" # audio codecs (AAC, MP3, FLAC, etc.)

# Cargo.toml — core crates are on crates.io [dependencies] wedeo = "0.1.2" wedeo-codec-h264 = "0.1.2" # H.264 decoder wedeo-format-mp4 = "0.1.2" # MP4 demuxer wedeo-symphonia = "0.1.2" # audio codecs (AAC, MP3, FLAC, etc.)

AV1 requires a git dependency (rav1d is not yet on crates.io)

wedeo-rav1d = { git = "https://github.com/sharifhsn/wedeo" }`

Build and test locally

cargo build cargo nextest run # or cargo test cargo clippy

cargo build cargo nextest run # or cargo test cargo clippy

Decode a file and compare against FFmpeg:

cargo run --release --bin wedeo-framecrc -- input.264 ffmpeg -bitexact -i input.264 -f framecrc -

cargo run --release --bin wedeo-framecrc -- input.264 ffmpeg -bitexact -i input.264 -f framecrc -

FATE testing

FFmpeg's native test suite.

./scripts/fetch-fate-suite.sh # downloads full suite (~1.2 GB) FATE_SUITE=./fate-suite cargo nextest run -p wedeo-fate

./scripts/fetch-fate-suite.sh # downloads full suite (~1.2 GB) FATE_SUITE=./fate-suite cargo nextest run -p wedeo-fate

JVT conformance (ITU test vectors)

204 test vectors from the ITU JVT conformance suite, with MD5 ground truth from the Fluster project. No FFmpeg required — comparison is against ITU-provided checksums.

python3 scripts/fetch_jvt.py # download vectors (~50 MB) python3 scripts/suite_runner.py --suite jvt-avc-v1,jvt-fr-ext --format yuv420p

python3 scripts/fetch_jvt.py # download vectors (~50 MB) python3 scripts/suite_runner.py --suite jvt-avc-v1,jvt-fr-ext --format yuv420p

The unified suite runner also wraps the FATE suites:

python3 scripts/suite_runner.py --suite all --format yuv420p python3 scripts/suite_runner.py --suite fate-cavlc --save-snapshot python3 scripts/suite_runner.py --suite fate-cavlc --check-snapshot # regression check

python3 scripts/suite_runner.py --suite all --format yuv420p python3 scripts/suite_runner.py --suite fate-cavlc --save-snapshot python3 scripts/suite_runner.py --suite fate-cavlc --check-snapshot # regression check

Architecture

wedeo/  crates/  wedeo-core/ libavutil — Rational, Buffer, Frame, Packet, errors  wedeo-codec/ libavcodec — Decoder/Encoder traits, codec registry  wedeo-format/ libavformat — Demuxer/Muxer traits, I/O, InputContext  wedeo-filter/ libavfilter (stub)  wedeo-resample/ libswresample (rubato)  wedeo-scale/ libswscale (dcv-color-primitives)  codecs/  wedeo-codec-h264/ H.264 decoder — 30K lines, NEON assembly, 55 benchmarks  wedeo-codec-pcm/ PCM codec — 17 formats  formats/  wedeo-format-h264/ H.264 Annex B demuxer  wedeo-format-wav/ WAV demuxer + muxer  wedeo-format-mp4/ MP4/MOV demuxer  adapters/  wedeo-symphonia/ Wraps symphonia (FLAC, Vorbis, MP3, AAC, WavPack)  wedeo-rav1d/ Wraps rav1d (AV1)  bins/  wedeo-cli/ CLI tool  wedeo-play/ Video player — wgpu+winit, ffplay-style A/V sync  tests/  fate/ FATE cross-validation harness  scripts/  suite_runner.py Unified conformance runner (FATE + JVT)  fetch_jvt.py JVT vector downloader  conformance_full.py FATE conformance report  regression_check.py Quick regression check  test_suites/  h264/ JVT manifest JSONs (tracked)

wedeo/  crates/  wedeo-core/ libavutil — Rational, Buffer, Frame, Packet, errors  wedeo-codec/ libavcodec — Decoder/Encoder traits, codec registry  wedeo-format/ libavformat — Demuxer/Muxer traits, I/O, InputContext  wedeo-filter/ libavfilter (stub)  wedeo-resample/ libswresample (rubato)  wedeo-scale/ libswscale (dcv-color-primitives)  codecs/  wedeo-codec-h264/ H.264 decoder — 30K lines, NEON assembly, 55 benchmarks  wedeo-codec-pcm/ PCM codec — 17 formats  formats/  wedeo-format-h264/ H.264 Annex B demuxer  wedeo-format-wav/ WAV demuxer + muxer  wedeo-format-mp4/ MP4/MOV demuxer  adapters/  wedeo-symphonia/ Wraps symphonia (FLAC, Vorbis, MP3, AAC, WavPack)  wedeo-rav1d/ Wraps rav1d (AV1)  bins/  wedeo-cli/ CLI tool  wedeo-play/ Video player — wgpu+winit, ffplay-style A/V sync  tests/  fate/ FATE cross-validation harness  scripts/  suite_runner.py Unified conformance runner (FATE + JVT)  fetch_jvt.py JVT vector downloader  conformance_full.py FATE conformance report  regression_check.py Quick regression check  test_suites/  h264/ JVT manifest JSONs (tracked)

Each FFmpeg library maps to one Rust crate. Codecs and formats register themselves via inventory at link time — no central enum.

CI

Five parallel jobs run on every PR (all required to merge):

• Lint — clippy + rustfmt

• Test — 462 unit and integration tests via nextest

• FATE Regression — no previously-passing FATE test may regress (framecrc vs FFmpeg)

• JVT Regression — no previously-passing JVT test may regress (MD5 vs ITU checksums)

• Deny — license allow-list and advisory audit via cargo-deny

Conformance baselines are committed in test_suites/baselines/. To update after expanding coverage:

python3 scripts/suite_runner.py --suite fate-cavlc,fate-cabac \  --save-snapshot --snapshot-dir test_suites/baselines

python3 scripts/suite_runner.py --suite fate-cavlc,fate-cabac \  --save-snapshot --snapshot-dir test_suites/baselines

Pre-commit hook available: pip install pre-commit && pre-commit install

FFmpeg reference

The FFmpeg/ submodule is pinned to n8.1. Optional — only needed to read the C source or build a debug FFmpeg for development:

git submodule update --init cd FFmpeg && ./configure --disable-optimizations --enable-debug=3 \  --disable-stripping --disable-asm && make -j$(nproc) ffmpeg

git submodule update --init cd FFmpeg && ./configure --disable-optimizations --enable-debug=3 \  --disable-stripping --disable-asm && make -j$(nproc) ffmpeg

Contributing

See CONTRIBUTING.md.

For AI agents

This repo is designed for AI-assisted development. CLAUDE.md contains the full project context: architecture, conventions, debugging procedures, and technical requirements. It is the canonical reference for any AI agent working on this codebase — read it before writing code.

The llms.txt file provides a machine-readable project summary following the llms.txt convention.

License

LGPL-2.1-or-later. See LICENSE and COPYING.LGPLv2.1.