Alberto Trigo

Using an Android device as a webcam

Configure your system to use your Android phone as a webcam using scrcpy with a virtual video device /dev/video10 that persists across reboots.

Prerequisites

1. Install Required Software

Ensure the following packages are installed:

  • scrcpy: For Android screen mirroring and video streaming.
  • v4l2loopback-dkms: To create a virtual video device.
  • ffmpeg: For processing video streams.

2. Enable USB Debugging on Android

  • Go to Settings → About Phone → Tap “Build Number” seven times to enable Developer Options.
  • In Developer Options, enable USB Debugging.

3. Connect Your Android Phone

Use a USB cable to connect your Android device to your computer.

Step 1: Configure v4l2loopback

1.1. Create a Configuration File

Create a file to define v4l2loopback options:

sudoedit /etc/modprobe.d/v4l2loopback.conf

Add the following:

options v4l2loopback devices=1 video_nr=10 card_label="Android Webcam" exclusive_caps=1

1.2. Create a Systemd Service

Ensure the kernel module is loaded at boot:

sudoedit /etc/systemd/system/v4l2loopback.service

Add the following:

[Unit]
Description=Load v4l2loopback kernel module
After=systemd-modules-load.service
Before=graphical.target

[Service]
Type=oneshot
ExecStart=/usr/bin/modprobe v4l2loopback
ExecStartPost=/usr/bin/udevadm settle
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Enable the service:

sudo systemctl enable v4l2loopback.service

Step 2: Integrate with Dracut

2.1. Add v4l2loopback to Dracut Configuration

Create a configuration file for dracut:

sudoedit /etc/dracut.conf.d/v4l2loopback.conf

Add the following:

add_drivers+="v4l2loopback"

2.2. Regenerate the Initramfs

Rebuild the initramfs:

sudo dracut --force

Step 3: Test the Configuration

Reboot your system:

sudo reboot

After rebooting, confirm /dev/video10 exists:

ls /dev/video10

If it exists, the configuration is successful. If not, check:

  • The systemd service status: sudo systemctl status v4l2loopback.service
  • Kernel logs: sudo dmesg | grep v4l2loopback

Step 4: Run scrcpy to Use Android as a Webcam

Use the following command to start streaming your Android device’s camera to /dev/video10:

scrcpy --video-source=camera --camera-ar=1:1 --no-audio --video-codec=h264 --capture-orientation=0 --v4l2-sink=/dev/video10

Command Breakdown:

  • --video-source=camera: Uses the phone’s camera as the video source.
  • --camera-ar=1:1: Sets the aspect ratio to 1:1.
  • --no-audio: Disables audio streaming.
  • --video-codec=h264: Uses the H.264 codec for video encoding.
  • --capture-orientation=0: Disables orientation-based adjustments.
  • --v4l2-sink=/dev/video10: Streams the video output to /dev/video10.

Troubleshooting

  1. Device Not Created:

    • Verify the kernel module is loaded: sudo lsmod | grep v4l2loopback
    • Check logs: sudo dmesg | grep v4l2loopback

  2. Access Denied: Ensure your user has permission to access video devices:

    sudo usermod -aG video $USER

  3. Poor Performance: Adjust scrcpy options, such as --bit-rate or resolution, to optimize performance.