There are good working tools already out there, a very easy one to use is Kazam.
However, I was looking for a tool which can downscale the video, while still recording the speakers audio and my microphone.
So, Kazam is easy to use but you can’t configure much. It has no option to downscale the video.
SimpleScreenRecorder offers way more options, especially for encoding, but it is not easy to record speakers and microphone.
I ended up using ffmpeg, a user-unfriendly command line tool. It worked, but audio was very low volume. Please see below for the audio fix.
Fixing the colors
While SimpleScreenRecorder recorded the colors of the screen as they were, I had slightly shifted colors in ffmpeg and Kazam. I was able to fix it for ffmpeg by using libx264rgb instead of libx264. See the screenshot below, top is wrong colors, bottom is correct colors:
Fixing the audio
I figured out the volume of my PulseAudio device was set to 20% for whatever reason.
So first, list all your PulseAudio devices:
On my PC, the output looks like this:
The following command set the volume level to 100%, you can validate it by calling “pacmd list-sources” again.