Define the dimension of the video in a view item
You can choose to maintain the original dimensions of the video or stretch it to fill the view item.
Select the view and the camera view item containing the video stream you want to adjust.
On the Properties pane, use the Maintain image aspect ratio option:
Select to keep the dimensions of the original video. This option can result in black space around the video.
Clear to stretch the video to fill the view item. This option fills the view item uniformly but may distort the video.