Linux Video Conferencing and Streaming using OBS, Gstreamer, and FFmpeg

There's currently a market shortage in standard USB webcams due to current events causing many people to be working from home. I didn't manage to buy one before they all sold out, but I own a DSLR and I have a few IP security apartments in my apartment. I figured I'd try to use them for video conferencing as a proof-of-concept.

I'm running Ubuntu 18.04. Instructions may differ for other distributions.

OBS Studio isn't strictly required, but it can be useful for easy color correction and other video broadcasting tools. If you want to use multiple webcams as sources, then it is required. That said, for those who don't want to use OBS you can use the V4L2 device that you're piping the IP camera video to as the video source.

Browser support

Here's my success with using the techniques described below with various web browsers on Linux.

Using OBS Studio as a webcam video source

• Firefox: It works
• Google Chrome: It works

Using Gstreamer as a video source without OBS

• Firefox: I haven't gotten it to work
• Google Chrome: It works

Using FFmpeg as a video source without OBS

• Firefox: It works
• Google Chrome: It works

Camera Setup

The DSLR shouldn't require any special setup. I'm using mine with the USB cable that came with it. The most it takes for setup is lens selection and camera placement. Beyond that, if it is supported by gphoto2 (most Nikon and Canon cameras are), then it should be good to go.

In order for this to work, you need to have an IP camera capable of producing RTSP streams. I am using the Wyze cam since I have one lying around, but any camera capable of being an RTSP video source should work. RTSP setup for cameras varies from manufacturer to manufacturer, so I can't cover them all.

• Wyze Cam RTSP Setup

Fundamentally, what you'll need is the RTSP URI. On Wyze cams with RTSP enabled, it looks like:

rtsp://username:password@WYZE_CAM_IP/live

This will be different for other camera manufacturers.

Linux Setup

Prerequisite packages

The following Ubuntu packages are necessary for this tutorial, which can be installed via apt.

• v4l2loopback-utils
• gstreamer1.0-tools
• obs-studio
• gphoto2

I forget which gstreamer plugin set that I needed to get to get stuff working, but I have the good, bad, and ugly plugin packages installed from the Ubuntu repositories, as well as the gstreamer1.0-libav plugin package.

Setting up Video4Linux

In order to treat an IP camera as a webcam, Linux needs to pipe the video feed into a virtual camera device. This can be done by loading the v4l2loopback kernel module to create virtual video devices that OBS can read from and write to. Let's say that you want to create a video device for OBS to output to and have two camera sources that you want to use as video sources. The following command will set that up for you.

$ sudo modprobe v4l2loopback video_nr=10,11,12 card_label="OBS Video","Camera 1",Camera 2" exclusive_caps=1,1,1

The stock v4l2loopback Ubuntu packages let you create a maximum of eight devices using v4l2loopback and modprobe.

If you ls /dev/video*, you should see the devices /dev/video10, /dev/video11, and /dev/video12. You're all set up.

Automatically loading v4l2loopback on boot

The above command for setting up v4l2 devices via modprobe will not persist after reboot. However, it is possible to configure Linux to automatically configure the virtual cameras at boot time with a couple of configuration files. It will be assumed that the video setup in this configuration is the same as what was created from the modprobe command listed above. Feel free to adjust as necessary for the video setup that you need.

Place the following contents in /etc/modprobe.d/v4l2loopback.conf:

options v4l2loopback video_nr=10,11,12 card_label="OBS Video","Camera 1","Camera 2" exclusive_caps=1,1,1

Place the following contents in /etc/modules-load.d/v4l2loopback.conf:

v4l2loopback

If you reboot your computer, you should see the devices /dev/video10, /dev/video11, and /dev/video12 automatically configured for you.

Capturing Video

Capturing from the DSLR

Capturing with the DSLR is fairly straightforward. That said, before running gphoto2, Ubuntu may have the gvfs daemon auto-detecting and auto-claiming the camera's USB interface. This is can be mitigated by killing the relevant gvfs processes:

$ killall -9 gvfs-gphoto2-volume-monitor
$ killall -9 gvfsd-gphoto2

Once those processes have been killed, the following command will pipe the DLSR camera feed to video device:

$ gphoto2 --stdout --capture-movie | gst-launch-1.0 fdsrc fd=0 ! decodebin name=dec ! queue ! videoconvert ! tee ! v4l2sink device=/dev/video11

For convenience, I've added the script v4l2-gphoto2 to run these three commands.

Capturing the IP Camera

Now that your video devices are set up, it's time to start piping the RTSP stream into them. The following command takes one RTSP stream encoded as h264 video (many IP cameras encode with h264 or h265 by default), decodes it, and puts it into a video device:

$ gst-launch-1.0 rtspsrc drop-on-latency=true location=<rtsp uri> ! decodebin ! videoconvert ! v4l2sink device=/dev/video12

See the rtspsrc and v4l2sink gstreamer documentation for more options for configuring the gstreamer pipeline for the IP camera device.

Once you have gstreamer launched for all of the cameras you're using, you can configure them for usage with OBS Studio as V4L2 Video Capture Devices.

FFmpeg equivalent command

If you prefer FFmpeg to Gstreamer, the following command pipes video from an IP camera to V4L2 device. Note that you need to manually set up the frame rate and resolution (I'm using 1920x1080 in the example).

$ ffmpeg -i <rtsp uri> -r 30 -s 1920x1080 -vcodec rawvideo -pix_fmt yuv420p -f v4l2 -vf scale=1920x1080 /dev/video12

I generally prefer Gstreamer to FFmpeg since there's less that I need to know about the video source a-priori, but if you don't want to use OBS and are a Firefox user, then I recommend using FFmpeg instead of Gstreamer for piping video to a V4L2 device.

Configuring OBS Studio to output to a V4L2 device.

By default OBS doesn't have the capability of outputting video to a V4L2 device. However, there is a plugin that can be used for that. This is required to use the output of OBS for video conferencing. Instructions for installing the OBS V4L2 output plugin can be found at the obs-v4l2sink GitHub page.

Once you have that installed, you can use /dev/video10 (or whatever you've configured as the OBS output device via v4l2loopback on your system) with the V4L2 output plugin under the OBS tools menu.

Audio

My instructions above do not mention audio. While some IP cameras have audio, I prefer to use an actual dedicated microphone for video conferencing. The Linux application I use for configuring my audio setup is called pavucontrol. Nothing special needs to be done to set up Linux audio on Ubuntu if the stock microphone sound options are suitable for you. However it should be worth pointing out that if you're using an IP camera, there will be some video latency between when you do something on the camera and when it shows up on screen in OBS. It may be necessary to add a manual audio latency to match the video latency. This can be done in pavucontrol from the Input Devices tab in the advanced settings for your microphone device. That said, I'm currently using my DSLR as my primary camera for video conferencing, so latency mismatches aren't a huge issue for me.