CamStream

An ad-free, open-source Android app that streams your phone's camera to your computer as a webcam: a from-scratch replacement for the closed-source, ad-supported DroidCam app that plugs straight into the existing open-source droidcam-linux-client / v4l2loopback-dc PC pipeline, unmodified.

No DroidCam code is reused anywhere in this project. The wire protocol was independently recovered by reading droidcam-linux-client's own GPL-2.0 source (published specifically so people can build interoperable clients) and reimplemented from scratch here. See PROTOCOL.md for the full wire-format writeup and provenance notes.

Features

• CameraX-based capture, JPEG-encoded, streamed over the DroidCam-compatible TCP protocol on port 4747
• Foreground service that keeps streaming while the screen is off or the app is backgrounded
• Front/back camera switching mid-stream, without dropping the PC connection
• Minimal, modern UI: connection status, the address to enter on the PC side (tap to copy), and start/stop/switch controls. Deliberately no camera preview in the UI itself, since rendering one would cost battery for no benefit
• Works with any client that speaks the protocol: droidcam-cli, the droidcam GUI, or a browser video call (e.g. Google Meet) via the resulting v4l2loopback device

Requirements

On the phone:

• Android 8.0 (API 26) or newer
• Developer Options → USB debugging enabled, to sideload the debug build

On the computer:

• droidcam-linux-client and its v4l2loopback-dc kernel module installed and working (e.g. on Arch/CachyOS, paru -S droidcam v4l2loopback-dc-dkms). This project doesn't touch or replace that pipeline; it's purely a new client for the phone side.
• Both devices on the same LAN/WiFi (this protocol has no NAT traversal or relay).

To build:

• JDK 17
• Android SDK (platform-tools, platforms;android-34, build-tools;34.0.0, or whatever the Gradle build reports it needs), installable via sdkmanager or Android Studio

Build

git clone <this-repo>
cd camstream
./gradlew assembleDebug

local.properties (gitignored) must contain sdk.dir=<path-to-your-android-sdk>, or set ANDROID_HOME/ANDROID_SDK_ROOT in your environment; Android Studio does this automatically on first sync.

Output: app/build/outputs/apk/debug/app-debug.apk.

Run

1. Install the APK: grab the latest one from Releases, or use your own build with adb install -r app/build/outputs/apk/debug/app-debug.apk.
2. Launch the app, grant the camera (and, on Android 13+, notification) permission, tap Start. The screen shows the phone's LAN IP and port 4747.
3. On the computer:

   droidcam-cli <phone-ip> 4747
   

   or launch the droidcam GUI and enter the same address. Confirm a live feed appears on the resulting /dev/videoX in cheese, OBS, or a browser webcam test page.
4. To use it in a video call: the v4l2loopback device identifies itself as "Droidcam" in any camera picker. In Google Meet's pre-join screen, for example, pick it there to preview before joining.

Tap Front/back camera any time to switch; it rebinds without dropping the connection or changing the resolution the PC side already negotiated.

Project layout

• app/src/main/java/dev/camstream/app/CameraCapture.kt: CameraX ImageAnalysis → YUV_420_888 → JPEG, with front/back switching.
• app/src/main/java/dev/camstream/app/LatestFrameHolder.kt: single-slot latest-frame handoff (drop-frame-if-busy), so a slow network never backs up frames.
• app/src/main/java/dev/camstream/app/StreamingService.kt: foreground service (camera type), ServerSocket(4747), and the wire protocol itself.
• app/src/main/java/dev/camstream/app/MainActivity.kt: the entire UI.
• PROTOCOL.md: the wire format this app implements.

Troubleshooting

• EADDRINUSE / "Server socket failed" in logcat, app stuck showing "Streaming" with no PC connection working: something else on the phone already has port 4747, most likely the official DroidCam app, if it's also installed and left running. Force-stop it (adb shell am force-stop com.dev47apps.obsdroidcam, or from Android settings), then retry. CamStream resets its own state automatically when the bind fails, so a fresh Start is enough.
• PC client prints Connection reset! Is the app running?: check logcat for the actual StreamingService error to see whether the port bind failed for a different reason (another instance already running, an adb reverse conflict, etc.).

Not implemented

• avc/H.264 codec path (currently jpg only)
• Audio (CMD /v2/audio)
• USB/adb reverse transport (WiFi only for now)
• Zoom/AF/flash control channel (CMD /v1/ctl?...)

Contributions welcome: PRs and issues both.

License

MIT. See LICENSE.

This project only talks to droidcam-linux-client over the network protocol described in PROTOCOL.md; no GPL-licensed source is included, linked, or bundled here, so its GPL-2.0 license doesn't extend to this codebase. The two projects are independent and separately licensed; this one just happens to be wire-compatible with the other.

Credits

• dev47apps/droidcam-linux-client (GPL-2.0): the PC-side pipeline this app is compatible with, and the source read to recover the wire protocol.
• google/material-design-icons (Apache-2.0): icon glyphs used in the UI.