Pixel Aspect Ratio

Pixel aspect ratio (PAR) is the ratio of the width to height of a single pixel in a video frame, as opposed to the entire frame. A 1:1 PAR indicates square pixels, common on PC displays.

The pixel aspect ratio of a video stream can be computed from the display aspect ratio (usually 4:3 or 16:9) and the frame width and height. For example, a DVD 4:3 video stream encoded at 720x480 would have a PAR of (4*480):(3*720), or 8:9; the same stream encoded at 704x480 would have a PAR of 10:11.