DV and DVD video, for all


DV and DVD video, for all practical purposes, are 720X480. The pixel aspect ratio determines if its 4X3, 16X9, or something else. DV video uses a 0.9 pixel aspect ratio so the image is a bit narrower than the square 1.0 pixel. Letterbox is 1.3 (I think).

Anyways, a television does crop off a small portion of the video edges. This is called "Overscanning". The reason is due to older analog video, especially with VHS tapes. The video sync signal tells when to start the picture scan and when to jump to the next line. Analog signals fluctuate ever so slightly so in order for the next line to start at the correct time, a tiny portion of the line being drawn does NOT get completed. This typically happens on each line. The result is a black "noisy" stripe along the right edge of the video picture. Overscanning hid this. Digital video corrected the problem rather than hide it.

When you play your DV video, its displaying every pixel. No cropping. If your video was captured from an analog source, you’ll see the black stripe. Most software media players read the pixel aspect ratio code in the file and displays it accordingly. From time to time you may encounter a video file that the ratio is all out of whack. Its not a display problem, its the pixel ratio code embedded in the file. Who ever made the file your viewing set the pixel aspect ratio incorrectly. (Unless the file is partly corrupt and the player couldn’t read the pixel aspect ratio information).

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