Digital Signal Processing Reference
In-Depth Information
shown the effect of interlaced video
for now just remember that
the resolution is halved when the video is interlaced. The table is
meant to make you aware of the amount of bits that are processed
when working with digital video. Digital video processing is
a demanding computational task
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especially at HD resolutions.
And the primary reason is the sheer number of pixels (and hence
bits) involved.
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2.3 Digital Video: Color Spaces
A color space is a method by which we can specify, create and
visualize color. Each pixel has a certain color, which in simple
terms can be described as a certain combination of red, blue and
green. Let's represent each value of the color by eight bits. If the
pixel is completely red, the R component of the pixel would be
1111 1111 and the other two components (blue and green) would
be 0000 0000.
When these values are added together all we see is red. If the
other two color values are not zero then the resultant color is
a combination of red and some blue and some green. This color
space is additive
the resultant pixel color is the sum of the
intensities of each of the colors. See
Figure 2.2
.
The RGB color model is used to display colors on older CRT
TVs as well as today's LCD TVs. Each value drives the excitations
of red, green and blue phosphors on the CRT faceplate. And for
digital TVs the resultant pixel value stored in hardware is con-
verted to voltage that fires that pixel on the screen. There is more
to this, including accounting for gamma correction, but we will
look at that later.
Printers describe a color stimulus in terms of the reflectance
and absorbance of cyan, magenta, yellow and black inks on the
paper. So they work in a different color space.
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R
G
PIXEL VALUE
B
Figure 2.2.
