Tiny Container Camera

Use your Android phone/tablet camera as a webcam on any website (Microsoft Teams, Google Meet, Zoom web, ...) in Firefox running inside Tiny Computer / tiny_container or any other proot environment.

Google Meet running in Firefox inside Tiny Computer on a Galaxy Tab S8, with video from the tablet's camera.

Tested on

Device	Samsung Galaxy Tab S8 5G (SM-X706B)
Chipset	Qualcomm Snapdragon 8 Gen 1 (SM8450)
RAM	8 GB
OS	Android 16, One UI 8.0 (not rooted)
Container	Tiny Computer (com.fct.tc4), Debian in proot
Browser	Firefox ESR 153.5
Camera app	IP Webcam (com.pas.webcam), 1280x720 MJPEG
Sites	Google Meet (call), webcamtoy.com

It has two parts:

1. Firefox extension: exposes the Android camera as a virtual webcam.
2. WebRTC fix (webrtc-fix/): makes video calls actually connect from Firefox inside proot on Android 11+.

Why?

Inside proot, Android's /dev/video* devices are not accessible without root, and v4l2loopback cannot be installed because kernel modules cannot be loaded. So the camera cannot be passed through as a regular V4L2 device (this includes scrcpy --v4l2-sink).

The extension takes a different route: the IP Webcam app on Android serves an MJPEG stream at http://127.0.0.1:8080/video, and the extension exposes that stream to web pages as a virtual camera through getUserMedia(). The microphone still uses the real audio input (PulseAudio).

IP Webcam (Android) ──MJPEG──▶ background.js ──port──▶ isolated.js ──postMessage──▶ main.js
                               (fetch, no CORS/CSP)                                 canvas.captureStream()
                                                                                    → getUserMedia() on the page

Video calls need one more fix. Android 11+ forbids apps from using netlink sockets, which Firefox uses to list local network addresses for WebRTC. With no addresses, Firefox gathers no ICE candidates and every call fails ("Sorry, we encountered a problem joining this video call."). webrtc-fix/ is a small LD_PRELOAD library that answers those netlink requests using ioctls that Android still allows.

Usage

1. IP Webcam on Android

Install IP Webcam (com.pas.webcam) from the Play Store, or via ADB:

adb shell am start -a android.intent.action.VIEW -d "market://details?id=com.pas.webcam"

Open IP Webcam, set Video preferences → Video resolution to 640x480 (recommended), then tap Start server.

2. Extension

Download the signed .xpi from the Releases page, then in Firefox (128+) open about:addons → gear icon → Install Add-on From File…

The options page opens after installing: click Save and grant access to let the extension read the stream from 127.0.0.1.

3. WebRTC fix

Needed for video calls (Teams, Meet, ...); not needed for camera-only sites. Requires gcc (sudo apt install gcc).

sh webrtc-fix/install.sh

This builds the library into ~/.local/lib/tiny-container-camera/ and makes Firefox ESR start with it (app menu, links opened from other apps, and the firefox-esr command). Close every Firefox window and start it again. To undo: sh webrtc-fix/install.sh --uninstall.

To try it once without installing:

gcc -O2 -shared -fPIC -o /tmp/libnetlink_shim.so webrtc-fix/netlink_shim.c -ldl -lpthread
LD_PRELOAD=/tmp/libnetlink_shim.so firefox-esr

4. Join a meeting

Pick the Android Camera (Tiny Container) camera in the meeting settings.

Troubleshooting

Samsung: IP Webcam stops in the background

One UI freezes background apps ("Freecess"), so the IP Webcam server stops as soon as you switch back to Tiny Computer. Exclude it from battery optimization (Settings → Battery → Background usage limits → Never sleeping apps), or via ADB:

adb shell dumpsys deviceidle whitelist +com.pas.webcam
adb shell cmd appops set com.pas.webcam RUN_ANY_IN_BACKGROUND allow

The camera shows "No access to 127.0.0.1:8080"

Open the extension options in about:addons and click Save and grant access, then reload the page.

Changing the stream URL

Open the extension options in about:addons (for example, to use IP Webcam on another phone: http://192.168.1.10:8080/video). For hosts other than 127.0.0.1/localhost, Firefox will ask for access permission.

Checking the WebRTC fix

LD_PRELOAD=~/.local/lib/tiny-container-camera/libnetlink_shim.so ip -4 addr

should list your interfaces (without the library it fails with Cannot bind netlink socket: Permission denied). Set NETLINK_SHIM_DEBUG=1 to log the netlink requests the library answers.

Development

To try code changes without signing: about:debugging → This Firefox → Load Temporary Add-on… → select extension/manifest.json. Temporary add-ons are removed when Firefox closes.

sh build.sh builds dist/tiny-container-camera.xpi (unsigned). To sign it, use web-ext sign.

sh build.sh --debug also writes dist/debug-extension/, which sends every getUserMedia/enumerateDevices call made by pages to python3 tools/log_server.py (written to tcc.log).

Testing without a phone

python3 tools/mock_mjpeg.py --port 8080 image1.jpg image2.jpg

Then open http://127.0.0.1:8080/tcc-test.html and click Start camera.

Limitations

• Firefox 128+ only (uses world: "MAIN" content scripts).
• Frames are decoded from JPEG inside proot, so lower resolutions run smoother.
• The WebRTC fix reports IPv4 addresses only.
• Sites still ask for microphone permission as usual. No camera permission prompt appears because the camera is virtual.

License

MIT, see LICENSE.