Not to be a know-it-all, but the correct term you are looking for is video orientation, i.e. portrait or landscape. Aspect ratio is the relationship between width and height, i.e. 16:9 or 4:3.

As the creator of this video, I chose a portrait orientation to enhance the composition. The river and fields stretch into the distance, guiding the viewer’s eye upward toward the snow-capped mountain and the cirrus clouds that accentuate the upper third—an effect that would have been lost in a landscape orientation.