I have a video which contains camera footage and some title elements. When exporting, I only get the titles and black in between. I presume that I am doing something wrong.

This is the project:



And that is the exported video:



Is it apparent what I have to change in order to have a video which is the same the one in the preview pane?

You are on Linux or Windows? I see you render it out as “webm”. Try to export as MPG4.
If you are on Windows download version 18.04, there is the MPG4 render included.
And see here: viewtopic.php?f=265&t=151516&p=396245&hilit=windows+mp4#p396245

This is on Fedora 28.

I have the impression that the problem arose from my use of a video file with spaces (and colons) in its name. After restarting the program and loading the project, I did not see the video as well. So then it was consistent with the rendered output. I renamed the file and edited the XML project file, after that it has worked well.

With the next project I can try to isolate the problem and then file a bug report.