Letterbox versus pillarbox bars
Letterboxing describes bars above and below the picture. Pillarboxing describes bars at its left and right. Their direction helps you see how the active picture differs from the surrounding canvas.
Baked-in borders and player-added bars
Baked-in bars are pixels inside the video file. Removing them requires a crop or a dedicated selection process. Player-added bars are outside the active video; changing the player or delivery aspect ratio may solve that problem without altering the recording.
Fill unused space without stretching the subject
After cropping only the outer borders, fit the active picture into the target shape. The checkerboard marks the area intended for new scenery. The examples contain encoded black borders so you can try detection and framing.
Preview a portrait video in a landscape canvas