Using Android device as a high resolution webcam on Linux

Problem

When working remotely, a good quality audio/video setup can be very handy in effective communication. Unfortunately, most of the non-Apple laptops come with underwhelming webcams even in 2024. I considered buying a better quality webcam but shelling out about $100 for a decent 1080p webcam didn’t make much sense. While looking for alternate solutions, I realized that I had a couple of older Android smartphones laying around with decent cameras.

Enter: this post.

Essential components:

• An Android smartphone with ‘Developer Options’ enabled
• A Linux workstation/laptop with v4l2loopback, adb, and scrcpy utilities.

Solution

v4l2loopback builds upon the Video4Linux platform. The Video4Linux toolset allows you to capture realtime video from a myriad of sources. The v4l2loopback kernel module allows us to create loopback video capture devices. Another important part of the solution is the scrcpy utility that can be configured to mirror an Android smartphone’s display, and sink the incoming video from the Android smartphone to the loopback video device created using v4l2loopback. This explanation probably seems far more complex than the actual setup, so let’s move on to the required commands:

Setting up prereqs:

1. Enabling ‘Developer Options’ on your Android device: The exact procedure may vary from vendor to vendor. On my device, it involved finding the ‘Build Number’ details in the phone Settings, and then tapping the ‘Build Number’ seven times.
2. Installing required tools on Linux workstation: You need to install v4l2loopback kernel module and scrcpy and adb utilities. Different distros package these utilities differently. On Arch Linux, I had to do pacman -S v4l2loopback-dkms android-tools scrcpy.

Setting up a v4l2loopback device

sudo /usr/bin/modprobe v4l2loopback devices=1 video_nr=2 exclusive_caps=1 card_label="AndroidWebCam"

Here is a brief explanation of the tricky parts:

• The video_nr=2 parameter tells v4l2loopback that I want the loopback device to be accessible at /dev/video2
• exclusive_caps=1 resolves issues with Chrome/Chromium browsers
• The card_label sets the name of the webcam as it will be shown in Google Meets and other video conferencing tools

Mirroring Android display

Now that the video loopback device has been created, we can use scrcpy to mirror the Android screen and dump the incoming traffic to /dev/video2:

/usr/bin/scrcpy --v4l2-sink=/dev/video2 --no-audio-playback

The --no-audio-playback switch tells scrcpy not to mirror audio from the Android device as I have a separate headset setup as my audio out and mic.

Note: The scrcpy utility simply mirrors your Android display. You can use Open Camera, and set the ‘Immersive Mode’ to ‘Hide everything’ so your Android display shows your camera. Another troubleshooting hint is that scrcpy mirrors your entire Android display by default. You can change this behavior by passing the --crop argument.

Script for automatic launch

To avoid entering all those commands manually, I have setup this script that I can execute whenever I want to start the AndroidWebcam.

#!/bin/bash

sudo /usr/bin/modprobe -r v4l2loopback
sudo /usr/bin/modprobe v4l2loopback devices=1 video_nr=2 exclusive_caps=1 card_label="AndroidWebCam"

sudo -u $USER /usr/bin/scrcpy --v4l2-sink=/dev/video2  --no-audio-playback

Results

I haven’t had an issue with this setup for the last couple of months. My video quality, including the color accuracy, refresh rate, skin texture, has improved considerably compared to my old 720p Logitech webcam. Perhaps thanks to the higher resolution and better color quality, the background blur effects also work much better now.