<p align="center">
<img src="https://raw.githubusercontent.com/Michael-A-Kuykendall/muxide/main/assets/muxide-logo.png" alt="Muxide" width="350"><br>
<strong>The last mile from encoder to playable MP4.</strong><br><br>
<a href="https://crates.io/crates/muxide"><img src="https://img.shields.io/crates/v/muxide.svg" alt="Crates.io"></a>
<a href="https://docs.rs/muxide"><img src="https://docs.rs/muxide/badge.svg" alt="Documentation"></a>
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</p>
<p align="center">
<code>cargo add muxide</code>
</p>
---
> **Muxide** takes correctly-timestamped, already-encoded audio/video frames and produces a standards-compliant MP4 — **pure Rust, zero runtime dependencies, no FFmpeg.**
<table>
<tr>
<td align="center"><strong>Your Encoder</strong><br><sub>H.264 / HEVC / AV1<br>AAC / Opus</sub></td>
<td align="center">➡️</td>
<td align="center"><strong>Muxide</strong><br><sub>Pure Rust<br>Zero deps</sub></td>
<td align="center">➡️</td>
<td align="center"><strong>playable.mp4</strong><br><sub>Standards-compliant<br>Fast-start ready</sub></td>
</tr>
</table>
---
## Why Muxide Exists
If you're building a recording pipeline in Rust, you know the tradeoffs:
| **FFmpeg CLI/libs** | External binary, GPL licensing concerns, "which build is this?" |
| **GStreamer** | Complex plugin system, C dependencies, heavy runtime |
| **Raw MP4 writing** | ISO-BMFF expertise required (sample tables, interleaving, moov layout) |
| **"Minimal" crates** | Often missing fast-start, strict validation, or production ergonomics |
Muxide solves **one job cleanly**:
> Take already-encoded frames with correct timestamps → produce a **standards-compliant, immediately-playable MP4** → using **pure Rust**.
Nothing more. Nothing less.
## Core Invariant
Muxide enforces a strict contract:
| ✓ Frames are already encoded | ✓ Valid ISO-BMFF (MP4) |
| ✓ Timestamps are monotonic | ✓ Correct sample tables |
| ✓ DTS provided for B-frames | ✓ Fast-start layout |
| ✓ Codec headers in keyframes | ✓ No post-processing needed |
If input violates the contract, Muxide **fails fast** with explicit errors—no silent corruption, no guessing.
---
## Features
| **Video** | H.264/AVC | Annex B format |
| | H.265/HEVC | Annex B with VPS/SPS/PPS |
| | AV1 | OBU stream format |
| **Audio** | AAC | All profiles: LC, Main, SSR, LTP, HE, HEv2 |
| | Opus | Raw packets, 48kHz |
| **Container** | Fast-start | `moov` before `mdat` for web playback |
| | B-frames | Explicit PTS/DTS support |
| | Fragmented MP4 | For DASH/HLS streaming |
| | Metadata | Title, creation time, language |
| **Quality** | World-class errors | Detailed diagnostics, hex dumps, JSON output |
| | Production tested | FFmpeg compatibility verified |
| | Comprehensive testing | 80+ tests, property-based validation |
### Design Principles
| 🦀 **Pure Rust** | No unsafe, no FFI, no C bindings |
| 📦 **Zero deps** | Only `std` — no runtime dependencies |
| 🧵 **Thread-safe** | `Send + Sync` when writer is |
| ✅ **Well-tested** | Unit, integration, property tests |
| 📜 **MIT license** | No GPL, no copyleft concerns |
| 🚨 **Developer-friendly** | Exceptional error messages make debugging 10x faster |
> **Note:** `no_std` is not supported. Muxide requires `std::io::Write`.
---
## Quick Start
```rust
use muxide::api::{MuxerBuilder, VideoCodec, AudioCodec, Metadata};
use std::fs::File;
fn main() -> Result<(), Box<dyn std::error::Error>> {
let file = File::create("recording.mp4")?;
let mut muxer = MuxerBuilder::new(file)
.video(VideoCodec::H264, 1920, 1080, 30.0)
.audio(AudioCodec::Aac, 48000, 2)
.with_metadata(Metadata::new().with_title("My Recording"))
.with_fast_start(true)
.build()?;
// Write encoded frames (from your encoder)
// muxer.write_video(pts_seconds, h264_annex_b_bytes, is_keyframe)?;
// muxer.write_audio(pts_seconds, aac_adts_bytes)?;
let stats = muxer.finish_with_stats()?;
println!("Wrote {} frames, {} bytes", stats.video_frames, stats.bytes_written);
Ok(())
}
```
<details>
<summary><strong>📹 More Examples: HEVC, AV1, Opus, Fragmented MP4</strong></summary>
### HEVC/H.265 (4K)
```rust
// Requires VPS, SPS, PPS in first keyframe
let mut muxer = MuxerBuilder::new(file)
.video(VideoCodec::H265, 3840, 2160, 30.0)
.build()?;
muxer.write_video(0.0, &hevc_annexb_with_vps_sps_pps, true)?;
```
### AV1
```rust
// Requires Sequence Header OBU in first keyframe
let mut muxer = MuxerBuilder::new(file)
.video(VideoCodec::Av1, 1920, 1080, 60.0)
.build()?;
muxer.write_video(0.0, &av1_obu_with_sequence_header, true)?;
```
### Opus Audio
```rust
// Opus always uses 48kHz internally (per spec)
let mut muxer = MuxerBuilder::new(file)
.video(VideoCodec::H264, 1920, 1080, 30.0)
.audio(AudioCodec::Opus, 48000, 2)
.build()?;
muxer.write_audio(0.0, &opus_packet)?;
```
### Fragmented MP4 (DASH/HLS)
```rust
let mut muxer = MuxerBuilder::new(file)
.video(VideoCodec::H264, 1920, 1080, 30.0)
.fragmented(true) // Enable fMP4 mode
.build()?;
// Write frames, then flush fragments periodically
muxer.write_video(0.0, &frame, true)?;
muxer.flush_fragment()?; // Writes an moof+mdat pair
```
### B-Frames with Explicit DTS
```rust
// When encoder produces B-frames, provide both PTS and DTS
muxer.write_video_with_dts(
pts_seconds, // Presentation timestamp
dts_seconds, // Decode timestamp (for B-frame ordering)
&frame_data,
is_keyframe
)?;
```
</details>
---
## Command Line Tool
Muxide includes a command-line tool for quick testing and development workflows:
```bash
# Install the CLI tool
cargo install muxide
# Basic video-only muxing
muxide mux \
--video keyframes.h264 \
--width 1920 --height 1080 --fps 30 \
--output recording.mp4
# Video + audio with metadata
muxide mux \
--video stream.h264 \
--audio stream.aac \
--video-codec h264 \
--audio-codec aac-he \
--width 1920 --height 1080 --fps 30 \
--sample-rate 44100 --channels 2 \
--title "My Recording" \
--language eng \
--output final.mp4
# JSON output for automation
muxide mux --json [args...] > stats.json
# Validate input files without muxing
muxide validate --video input.h264 --audio input.aac
# Get info about supported codecs
muxide info
```
**Supported Codecs:**
- **Video:** H.264 (AVC), H.265 (HEVC), AV1
- **Audio:** AAC (all profiles), Opus
**Features:**
- Progress reporting with `--verbose`
- JSON output for CI/CD integration
- Comprehensive error messages
- Fast-start MP4 layout by default
- Metadata support (title, language, creation time)
---
## What Muxide Is Not
Muxide is intentionally **focused**. It does **not**:
| Encoding/decoding | Use `openh264`, `x264`, `rav1e`, etc. |
| Transcoding | Not a codec library |
| Demuxing/reading MP4 | Write-only by design |
| Timestamp correction | Garbage in = error out |
| Non-MP4 containers | MKV, WebM, AVI not supported |
| DRM/encryption | Out of scope |
**Muxide is the last mile**: encoder output → playable file.
---
## Use Cases
Muxide is a great fit for:
- 🎥 **Screen recorders** — capture → encode → mux → ship
- 📹 **Camera apps** — webcam/IP camera recording pipelines
- 🎬 **Video editors** — export timeline to MP4
- 📡 **Streaming** — generate fMP4 segments for DASH/HLS
- 🏭 **Embedded systems** — single binary, no external deps
- 🔬 **Scientific apps** — deterministic, reproducible output
Probably **not** a fit if you need encoding, demuxing, or legacy codecs (MPEG-2, etc.).
---
## Example: Fast-Start Proof
The `faststart_proof` example demonstrates a structural MP4 invariant:
- Two MP4 files are generated from the same encoded inputs
- One with fast-start enabled, one without
- No external tools are used at any stage
```text
$ cargo run --example faststart_proof --release
output: recording_faststart.mp4
layout invariant: moov before mdat = YES
output: recording_normal.mp4
layout invariant: moov before mdat = NO
```
When served over HTTP, the fast-start file can begin playback without waiting for the full download (player behavior varies, but the layout property is deterministic).
This example is intentionally minimal:
- Timestamps are generated in-code
- No B-frames/DTS paths are exercised
- The goal is container layout correctness, not encoding quality
---
## Performance
Muxide is designed for **minimal overhead**. Muxing should never be your bottleneck.
| 1000 H.264 frames | 264 µs | **3.7M frames/sec** |
| 1000 H.264 + fast-start | 362 µs | 2.8M frames/sec |
| 1000 video + 1500 audio | 457 µs | 2.2M frames/sec |
| 100 4K frames (~6.5 MB) | 14 ms | **464 MB/sec** |
<details>
<summary><strong>Run benchmarks yourself</strong></summary>
```bash
cargo bench
```
Benchmarks run on standard development hardware. In practice, **encoding is always the bottleneck** — muxing overhead is negligible.
</details>
---
## Input Format Requirements
<details>
<summary><strong>📋 Codec-specific requirements (click to expand)</strong></summary>
### H.264/AVC
- **Format:** Annex B (start codes: `00 00 00 01` or `00 00 01`)
- **First keyframe must contain:** SPS and PPS NAL units
- **NAL unit types:** IDR (keyframe), non-IDR, SPS, PPS
### H.265/HEVC
- **Format:** Annex B (start codes)
- **First keyframe must contain:** VPS, SPS, and PPS NAL units
- **NAL unit types:** IDR_W_RADL, IDR_N_LP, CRA, VPS, SPS, PPS
### AV1
- **Format:** OBU (Open Bitstream Unit) stream
- **First keyframe must contain:** Sequence Header OBU
- **OBU types:** Sequence Header, Frame, Frame Header, Tile Group
### AAC
- **Format:** ADTS (Audio Data Transport Stream)
- **Header:** 7-byte ADTS header per frame
- **Profiles:** LC-AAC recommended
### Opus
- **Format:** Raw Opus packets (no container)
- **Sample rate:** Always 48000 Hz (Opus specification)
- **Channels:** 1 (mono) or 2 (stereo)
</details>
---
## Documentation
| [📚 API Reference](https://docs.rs/muxide) | Complete API documentation |
| [📜 Design Charter](docs/charter.md) | Architecture decisions and rationale |
| [📋 API Contract](docs/contract.md) | Input/output guarantees |
---
## FAQ
<details>
<summary><strong>Why not just use FFmpeg?</strong></summary>
FFmpeg is excellent, but:
- External binary dependency (distribution complexity)
- GPL licensing concerns for some builds
- Process orchestration overhead
- "What flags was this built with?" debugging
Muxide is a single `cargo add` with zero external dependencies.
</details>
<details>
<summary><strong>Can Muxide encode video?</strong></summary>
No. Muxide is **muxing only**. For encoding, use:
- `openh264` — H.264 encoding (BSD)
- `rav1e` — AV1 encoding (BSD)
- `x264`/`x265` — H.264/HEVC (GPL, via FFI)
</details>
<details>
<summary><strong>What if my timestamps are wrong?</strong></summary>
Muxide will reject non-monotonic timestamps with a clear error. It does not attempt to "fix" broken input — this is by design to ensure predictable output.
</details>
<details>
<summary><strong>Is Muxide production-ready?</strong></summary>
Yes. Muxide has an extensive test suite (unit, integration, property-based tests) and is designed for predictable, deterministic behavior.
</details>
---
## License
MIT — no GPL, no copyleft, no surprises.
---
<p align="center">
<em>Muxide is designed to be <strong>boring</strong> in the best way:<br>predictable, strict, fast, and invisible once integrated.</em>
</p>