Digital Signal Processing Reference
In-Depth Information
1080p
1920 × 1080
2,073,600 pixels
~2 × more pixels
720p
1280 × 720
921,600 pixels
~3 × more pixels
480p
720 × 480
345,600 pixels
~6 × more pixels
Figure 2.1. Increasing number of
pixels in each frame of video
It might be interesting to note that the old cathode ray tube
(CRT) TVs had only half of the pixels of even SD resolution shown
here
so going from a CRT TV to a new 1080p TV just gave your
eyes a feast of 12 times more pixels for each video frame.
The number of pixels makes a huge difference.
Take another example
e
when Apple created the new 'retina'
display on the iPhone 4 it proved extremely popular with
consumers. The new iPhone 4 had a resolution of 940
e
640 pixels
compared to the old iPhone 3, which had a resolution of
320
480. So Apple found a way to increase the number of pixels
on the same size screen by a factor of four.
The number of pixels also determines the complexity of the
hardware used to manipulate these pixels. Since all manipulation
is in terms of bits, let's see how pixels translate to bits.
2.2 Digital Video: Pixels and Bits
Each pixel has a unique color which is a combination of the
primary colors: red, blue and green. How much of red, how much
of blue and how much of green is the key. And this “howmuch” is
described precisely by the value of the pixel. The value of the pixel
is represented by bits and the more bits are available, the more
accurate the representation. Bear in mind however, that bits are
expensive to store, to manipulate and to transmit from one device
to the other. So a happy balance must be realized.
