51
Resolutions
Resolution in an analog or digital world is similar, but there are some important
differences in how it is defined. In analog video, an image consists of lines or
TV-lines since analog video technology is derived from the television industry. In a digital
system, an image is made up of square pixels.
The sections below describe the different resolutions that network video can provide.
They include NTSC, PAL, VGA, megapixel and HDTV.
6.1
NTSC and PAL resolutions
NTSC (National Television System Committee) and PAL (Phase Alternating Line) resolutions are
analog video standards. They are relevant to network video since video encoders provide such
resolutions when they digitize signals from analog cameras. Current PTZ network cameras and
PTZ dome network cameras also provide NTSC and PAL resolutions since such cameras today use
a camera block (which incorporates the camera, zoom, auto-focus and auto-iris functions) made
for analog video cameras, in conjunction with a built-in video encoder board.
In North America and Japan, the NTSC standard is the predominant analog video standard, while
in Europe and many Asian and African countries, the PAL standard is used. Both standards origi-
nate from the television industry. NTSC has a resolution of 480 lines and uses a refresh rate of 60
interlaced fields per second (or 30 full frames per second). A new naming convention, which
defines the number of lines, type of scan and refresh rate, for this standard is 480i60
(“i” stands for interlaced scanning). PAL has a resolution with 576 lines and uses a refresh rate of
50 interlaced fields per second (or 25 full frames per second). The new naming convention for this
standard is 576i50. The total amount of information per second is the same in both standards.
When analog video is digitized, the maximum amount of pixels that can be created is based on
the number of TV lines available to be digitized. The maximum size of a digitized image is typi-
cally D1 and the most commonly used resolution is 4CIF.
RESOLUTIONS - CHAPTER 6
