Apple Final Cut Pro 5 - Manual (Page 1707)

356 Part V Appendixes
Common video frame sizes are shown in the table below.
Width Height
Pixel
aspect ratio Screen
aspect ratio Description
320 240 1:1 4:3 Used for web distribution or offline video
editing
640 480 1:1 4:3 An early standard for analog-to-digital
video editing, and an ATSC video
specification
720 1 480 Height
greater than
width 4:3 NTSC DV and DVD image dimensions
720 1 486 Height
greater than
width 4:3 NTSC standard definition video dimensions
used for professional digital formats such as
Digital Betacam, D-1, D-5, as well as DVD
and DV.
720 1 576 Width
greater than
height 4:3 PAL standard definition video dimensions
used for all digital formats such as Digital
Betacam, D-1, D-5, as well as DVD and DV.
1280 720 1:1 16:9 A high definition video format, capable of
higher frame rates in exchange for smaller
image dimensions
1920 1280 1:1 16:9 A high definition video format with very
high resolution, comparable to the
resolution of a film projection print
1 In most video devices, only 704 or 708 pixels are actually used for picture information.
720 x 486 Versus 720 x 480
Another issue that comes up is the subtle difference between NTSC SD formats that
use 486 lines per frame (Digital Betacam, D-1, D-5) and formats that use 480 lines per
frame (DV, DVCPRO, DVD). Why is there this subtle difference? The reason is
simple: 480 is divisible by 16, and 486 isn’t. Divisibility by 16 is important for any
MPEG-like compression codec, because each frame is broken into 16 x 16 pixel blocks
(known as macroblocks) during compression. All of the video formats that use 480
lines per frame are DV or MPEG-based compressions, all of which use similar
approaches to compression.
The only time this should be a concern is if you are converting between a 486-line
format like Digital Betacam and a 480-line format like DVD. However, the absence of 6
lines is hardly noticeable on an analog television, especially at the top and bottom,
which is usually masked anyway.