A small application for piping output from libfreenect2 to a v4l2loopback device so the Kinect 2 can be used as a webcam in Linux.
The original Kinect for Xbox driver for Linux essentially exposes the raw RGB video stream from the Kinect. This worked well for the original Kinect because the video formats were widely supported by V4L2 clients. The Kinect 2 on the other hand emits JPEG frames. There is a Kinect 2 kernel module that works well but most clients don't support the MJPEG format which makes the module of limited use with mainstream applications.
It seemed like a bad idea to do JPEG parsing and colorspace conversions in a kernel module and the v4l2loopback is a stable kernel module that allows clients to do their work in userspace while still providing a standard V4L2 interface.
This application uses the libfreenect2 library to connect to the Kinect 2 and get RGB color frames and then uses libswscale to perform a colorspace conversion to YUV420 which is a much more generally supported format by v42l clients. Since JPEG decoding is a CPU intensive operation the application will only start the stream when client applications open a file handle to the v4l2loopback device and will close the video stream when all handles are closed.
You will need to have installed the libswscale5 and libfreenect2 packages in order to compile. Then to compile:
mkdir build
cd build
cmake .. && make
If you're using Ubuntu you can grab the packages from my PPA. If you want to install from source (from the build directory in the compiling step):
sudo cp kinect2pipe /usr/bin/kinect2pipe
cp ../contrib/systemd/kinect2pipe.service ~/.config/systemd/user/
First you'll need a v4l2loopback device which you can create by installing the v4l2loopback-dkms package. Then you can
create the loopback device by doing the following:
sudo modprobe v4l2loopback devices=1 video_nr=0 card_label=Kinect2 exclusive_caps=1
To add the device permanently add the following to /etc/modules:
v4l2loopback
Then add the following to /etc/modprobe.d/v4l2loopback.conf:
options v4l2loopback devices=1 video_nr=0 card_label=Kinect2 exclusive_caps=1
In the example above this should create a v4l2loopback device at /dev/video0. If you change the device number above
make sure to modify ~/.config/systemd/user/kinect2pipe.service to reflect the change. Then you can install and start
the service:
systemctl --user enable kinect2pipe
systemctl --user start kinect2pipe
You can then test everything is working using VLC (or any other V4L2 client):
vlc v4l2:///dev/video0
You should get video output:
