User Guide

Digital Video Components 301
Color Space
A color space is a mathematical representation of a set of colors. There are three main color
models:
• RGB (used in color computer graphics and color television)
• YIQ, YUV, and YCbCr (used in broadcast and television systems)
• CMYK (used in color printing)
When working with computer graphics, you are only concerned with RGB and YCbCr.
Computer monitors display RGB (red-green-blue) color; every color displayed on screen is a
mixture of red, green, and blue. YCbCr is the standard for DVD video and is somewhat more
complicated.
YCbCr is the color space defined by Recommendation ITU-R BT.601 (formerly know as
CCIR-601), where Y is the luminance component and Cb and Cr are the chrominance (color
difference) components. When encoding with MPEG-2, the 4:2:2 digital video signal is sub-
sampled down to 4:2:0.
4:2:2 YCbCr means that Y has been sampled at 13.5 MHz, while Cb and Cr were each
sampled at 6.75 MHz. Thus, for every two samples of Y, there is one sample each of Cb and
Cr. 4:2:0 YCbCr means that Y has been sampled at 13.5 MHz, while Cb and Cr were each
sampled at 6.75 MHz. Thus, for every two sample of Y, there is one sample each of Cb and
Cr.