Aspect Ratio: Typically 4:3 and 16:9 for most screen monitors
VIDEO IMAGE SPECIFICATIONS
SIGNAL SYSTEM: 525 lines, 60 fields NTSC color signal
EFFECTIVE PIXELS: 340 K (4:3), 300 K (16:9)
PICTURE SIZE: 704 x 480 pixels
COMPRESSION: MPEG2 (a standard for video and audio compression).
For NTSC DVD, its frame aspect ratio is 720 x 480 pixels at 29.97 fps
PIXEL ASPECT RATIO: the ratio of width to height of one pixel in an image.
FRAME ASPECT RATIO: the ratio of width to height in the frame dimensions of an image.
DV NTSC has a pixel aspect ratio of 0.9 and also a frame aspect ratio of 4:3
NTSC video capture cards produce in some cases a 4:3 frame aspect ratio, with 1.0 square pixel ratio.
WIDESCREEN video formats have a frame aspect ratio of 16:9
NTSC and PAL share a pixel aspect ratio (referred to as D1 Aspect Ratio, which is essentially rectangular), but this ratio differs from that used by computer monitors (which is square). If you display 0.9 rectangular pixels on a 1.0 square pixel monitor, images an motion appear distorted, however when displayed on a broadcast monitor, the images will be correct.