There are many posts on the internet about the main OBS application having a black screen. I too had this problem and nothing I tried fixed it. I am running Ubuntu 18 LTS and the problem persisted. Here is what I did to fix it:
- Using Ubuntus package manager (the orange suitcase icon) I removed OBS (If you installed it differently then with this package manger you will need to use a different process to remove it.)
- For Ubuntu 15.04 and following versions, FFmpeg is officially included:
sudo apt-get install ffmpeg
- sudo add-apt-repository ppa:obsproject/obs-studio
- sudo apt-get update
- sudo apt-get install obs-studio
Now when I started OBS and defined a “Media Source” in the “sources” box I had a preview of it in the main screen which had been black until I downloaded the new “obs-studio” in step 5 above.
Hope this helps.