Comment by nayuki

Never mind anamorphic DVDs, all of them use non-square pixels. The resolution of DVD is 720×480 pixels (or squared pixels, referring back to the article); this is a 3:2 ratio of pixel quantities on the horizontal vs. vertical axes. But the overall aspect ratio of the image is displayed as either 4:3 (SDTV) or 16:9 (HDTV), neither of which matches 3:2. Hence the pixel aspect ratio is definitely not 1:1.