Screen Recording With Webcam Overlay Using Ffmpeg

The point of this post is to capture the screen on an x11 with webcam overlay in the bottom right corner (as people usually do with obs).

Capture screen with x11grab

On x11 systems, we can capture the screen using -f x11grab with ffmpeg.

Typically the command looks like

ffmpeg -video_size 1366x768 -framerate 25 -f x11grab -i :0.0 screen-cap.mp4

Where we specify the resolution, frame rate and the offset for recording (here is 0,0 which is the top left corner).

Capture audio along with the screen grab

If we want to include audio as well (in this case we will use pulse).

ffmpeg -video_size 1366x768 -framerate 25 -f x11grab -i :0.0 -f pulse -ac 2 -i default screen-cap.mp4

Using x264 for output

Using libx264

ffmpeg -video_size 1366x768 -framerate 25 -f x11grab -i :0.0 \
    -f pulse -ac 2 -i default  -vcodec libx264 -preset fast \
    -crf 18 -pix_fmt yuv444p screen-cap.mp4

Capturing the webcam input

For webcam; the process is simple.

ffmpeg -f v4l2 -framerate 25 -video_size 640x480 -i /dev/video0 webcam-cap.mp4

Putting everything together

Let’s mix these two together, the aim is to play the screen capture in the background and setup an overlay of video capture on the bottom right corner. -filter_complex is the argument for doing that where we have to pass overlay=withth:height and the pixel format.

for example


Also instead of hardcoding width and height we can use variables main_w-overlay_w for the width and main_h-overlay_h for the height. So when everything is put together the command looks like:

ffmpeg -f x11grab -video_size 1366x768 -framerate 30 -i :0.0 \
       -f v4l2 -video_size 320x180 -framerate 30 -i /dev/video0 \
       -filter_complex 'overlay=main_w-overlay_w:main_h-overlay_h:format=yuv444' \
       -vcodec libx264 -preset ultrafast -qp 0 -pix_fmt yuv444p video.mp4