Why is there black bars around my video when using a static background?

When using a static background in combination with a video step, you need to ensure that the specified width and height of the video embedded into the step is at the same aspect ratio as your video. Most videos these days are 16:9 or 4:3, and the ratio can be calculated using a tool such as these...

16:9: https://www.size43.com/16by9-aspect-ratio-calculator/

4:3: https://www.size43.com/4by3-aspect-ratio-calculator/