pixel aspect ratio (PAR)
In most screen displays, the pixels are square with a height-to-width ratio of 1:1.
For digital video, the pixel geometry may change from square to rectangular. For example, for digital video according to BT.601, the pixel aspect ratio(PAR) is 0.89 for NTSC and 1.0667 for the PAL television standard, which is related to the specifications of pixels per line, number of lines, and aspect ratio.
At BT.601, the PAL television standard specifies 720 pixels per line, there are 576 pixels horizontally, and the aspect ratio is 4:3, which means that the pixel format of PAL images is rectangular, and slightly wider than higher. If the same image is viewed in anamorphic widescreen (16:9), then the PAR value changes to 1.422, meaning that the pixel is 42% wider than higher.
When displaying digital TV on PC monitors, the pixel geometry of one image format must be adapted to the other. Here, the adjustment factor is 1.06 and 0.94, respectively.