RTMP Virtual Camera for macOS

Receive RTMP video streams (e.g., from OBS, MeldStudio, or ffmpeg) and expose them as a native macOS virtual camera. Any app that uses a webcam — FaceTime, Zoom, Google Meet, QuickTime — can select "RTMP Virtual Camera" as a camera source.

Installation

1. Download the latest .dmg from Releases
2. Open the DMG and drag RTMPVirtualCamera to the Applications folder
3. Launch RTMPVirtualCamera from /Applications

First launch: macOS may show a security prompt. If so, go to System Settings → Privacy & Security and click Open Anyway.

Setup (one-time)

1. In the app, click Install Extension
2. macOS will ask you to approve the system extension — go to System Settings → Privacy & Security and allow it
3. The camera extension is now installed and will persist across reboots

Usage

1. Click Start Server (default port 1935)
2. (Optional) Click Generate Key to require a stream key for authentication
3. Point your RTMP source at the URL shown in the app:

From OBS / MeldStudio:

• Server: rtmp://localhost/live
• Stream Key: the key shown in the app (or anything if no key is set)

From ffmpeg:

# Test pattern
ffmpeg -f lavfi -i testsrc=duration=3600:size=1920x1080:rate=30 \
  -pix_fmt yuv420p -c:v libx264 -b:v 2M -f flv rtmp://localhost/live/YOUR_STREAM_KEY

# Stream a file
ffmpeg -re -i video.mp4 -c:v libx264 -pix_fmt yuv420p \
  -f flv rtmp://localhost/live/YOUR_STREAM_KEY

4. Open FaceTime, Zoom, Google Meet, or any video app and select RTMP Virtual Camera as your camera

Uninstalling

1. Launch the app and click Uninstall Extension
2. Approve the removal in System Settings if prompted
3. Delete RTMPVirtualCamera.app from /Applications

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How It Works

RTMP Source ──► Rust Server ──► H.264 Decode ──► Shared Memory ──► Camera Extension ──► macOS Apps
 (ffmpeg,       (port 1935)    (VideoToolbox)   (mmap NV12)       (CoreMediaIO)       (FaceTime,
  OBS, etc.)                                                                            Zoom, etc.)

Three-layer architecture:

1. rtmp-server (Rust) — RTMP protocol handling, TCP server, FLV demux
2. video-pipeline (Rust) — VideoToolbox H.264 hardware decoding, raw NV12 pixel output
3. Camera Extension (Swift) — CoreMediaIO system extension that reads frames from shared memory and exposes them as a virtual camera

IPC uses a double-buffered memory-mapped file at /Library/Application Support/RTMPVirtualCamera/rtmp_vcam_ring (~6.2MB: 64-byte header + 2× 1920×1080 NV12 frames).

Requirements (building from source)

• macOS 12.3+
• Xcode 15+
• Rust toolchain (rustup)
• An Apple Developer account (code signing required for system extensions)

Build from Source

# Build everything (Rust + Swift)
make build-all

# Install to /Applications
make install

# Run tests
make test

The Rust RTMP server binary is embedded inside the app bundle and managed from the UI — no need to run it separately.

CLI Usage

The server can also be run standalone (without the host app):

rtmp-vcam-app [OPTIONS]

Options:
  -p, --port <PORT>          RTMP listen port (default: 1935)
  -k, --stream-key <KEY>     Require stream key for publishing
  -v, --verbose              Enable debug logging
  -h, --help                 Show this help

Troubleshooting

Camera doesn't appear in apps

• Make sure the extension is installed: check System Settings → Privacy & Security → Camera
• Try restarting the app that should see the camera
• Check extension logs: log stream --predicate 'subsystem == "com.rtmpvcam.host.camera-extension"'

"Address already in use" error

• Another process is using port 1935. Find it with lsof -i :1935 and kill it, or use a different port.

Video is garbled or not showing

• Ensure your source uses H.264 with YUV 4:2:0: add -pix_fmt yuv420p to your ffmpeg command
• High 4:4:4 Predictive profile is not supported by VideoToolbox

Stream key rejected

• Check that your RTMP URL matches the key shown in the app: rtmp://localhost:<port>/live/<key>
• In OBS/MeldStudio, the stream key goes in the "Stream Key" field, not the server URL

Server won't stop / orphaned process

• The server auto-exits if the host app dies. If a process is stuck: lsof -i :1935 to find it, then kill <PID>

Project Structure

rtmp-vcam/
├── Cargo.toml                    # Rust workspace
├── Makefile                      # Build orchestration
├── scripts/
│   ├── make-dmg.sh               # DMG packaging
│   └── release.sh                # Build + tag + GitHub release
├── crates/
│   ├── rtmp-server/              # RTMP protocol + TCP server
│   ├── video-pipeline/           # VideoToolbox H.264 decode (raw C FFI)
│   └── rtmp-vcam-app/            # Main binary (wires RTMP → decode → IPC)
└── swift/
    └── CameraExtension/          # Xcode project
        ├── HostApp/              # App UI (extension + server management)
        └── Extension/            # CoreMediaIO camera extension

Notes

• FaceTime mirrors the camera preview (like a real webcam). The remote viewer sees it correctly.
• The camera extension runs in a sandboxed process — IPC uses file-backed mmap under /Library/Application Support/ since POSIX shared memory and IOSurface are blocked by the sandbox.
• The server process auto-exits if the host app is killed, preventing orphaned processes.

License

MIT — free to use, modify, and distribute with attribution.