openscreen/electron/native

Native capture helpers

Windows native recording is resolved from one of these locations:

1. OPENSCREEN_WGC_CAPTURE_EXE, for local development and diagnostics.
2. electron/native/wgc-capture/build/wgc-capture.exe, for a locally built Ninja helper.
3. electron/native/wgc-capture/build/Release/wgc-capture.exe, for a locally built multi-config helper.
4. electron/native/bin/win32-x64/wgc-capture.exe or electron/native/bin/win32-arm64/wgc-capture.exe, for packaged prebuilt helpers.

Build the Windows helper with:

npm run build:native:win

The build writes the CMake output to electron/native/wgc-capture/build/wgc-capture.exe and copies the redistributable binary to electron/native/bin/win32-x64/wgc-capture.exe.

The helper contract is process-based: the app starts the process with one JSON argument and sends commands on stdin. stop\n finalizes the recording. During migration the helper prints both newline-delimited JSON events and the legacy text messages Recording started / Recording stopped. Output path: <path>.

Current V2 JSON shape:

{
  "schemaVersion": 2,
  "recordingId": 123,
  "sourceType": "display",
  "sourceId": "screen:0:0",
  "displayId": 1,
  "windowHandle": null,
  "outputPath": "C:\\path\\recording-123.mp4",
  "videoWidth": 1920,
  "videoHeight": 1080,
  "fps": 60,
  "captureSystemAudio": false,
  "captureMic": false,
  "microphoneDeviceId": "default",
  "microphoneGain": 1.4,
  "webcamEnabled": true,
  "webcamDeviceId": "default",
  "webcamDeviceName": "Camera (NVIDIA Broadcast)",
  "webcamWidth": 1280,
  "webcamHeight": 720,
  "webcamFps": 30,
  "outputs": {
    "screenPath": "C:\\path\\recording-123.mp4"
  }
}

The current helper implementation supports display/window video capture, system audio loopback, default-microphone capture, and Media Foundation webcam capture. Webcam frames are currently composed into the primary MP4 as a bottom-right picture-in-picture overlay. Browser deviceId values do not always map to Media Foundation symbolic links, so the renderer passes both webcamDeviceId and webcamDeviceName. The helper treats the Media Foundation friendly name as the preferred stable selector, then tries the browser id, and only falls back to the default webcam with an explicit warning when no requested device matches.

Smoke-test the helper with:

npm run test:wgc-helper:win
npm run test:wgc-window:win
npm run test:wgc-audio:win
npm run test:wgc-mic:win
npm run test:wgc-mixed-audio:win
npm run test:wgc-webcam:win

To validate a specific native webcam manually:

$env:OPENSCREEN_WGC_TEST_WEBCAM_DEVICE_NAME = "NVIDIA Broadcast"
npm run test:wgc-webcam:win
Remove-Item Env:OPENSCREEN_WGC_TEST_WEBCAM_DEVICE_NAME