Television & Video
Technology
Television Systems
A television system involves equipment located at the source of production, equipment
located in the home of the viewer, and equipment used to convey the television signal
from the producer to the viewer. television system involves equipment located at the
source of production, equipment located in the home of the viewer, and equipment used to
convey the television signal from the producer to the viewer.
A television system must be designed, therefore, to embrace the essential capabilities of
these senses, particularly the sense of vision.
•
Aspect of visual is the ability of the human eye to distinguish the brightness,
colors, details, sizes, shapes, and positions of objects in a scene before it.
•
Aspects of hearing include the ability of the ear to distinguish the pitch, loudness,
and distribution of sounds.
Video
A video signal is a sequence of still pictures. In order to feel the movement there
should be a certain number of still pictures per unit of time. Human visual
system can process 10 to 12 images per second. So in order to perceive any
motion at all, we need the number of still images (frames) to exceed ten.
Broadcast Video Standards
Three analog broadcast video standards are commonly in use around the world: NTSC,
PAL, and SECAM.
In Kenya the PAL technology is being phased out, the United States, the NTSC standard
is being phased out, replaced by ATSC digital television standard. It is important to
know where your multimedia project will be used.
A video recorded in USA which uses NTSC will not play on a television set in Kenya or
any European country (using PAL or SECAM),
Each system is based on a different standard that defines the way information is
encoded to produce the electronics signal that ultimately creates a television picture.
Dubbing between standards requires high-end specialized equipment.
National Television Standard Committee
(NTSC)
N. America and parts of S. America use a system for broadcasting and displaying video
that is based upon specifications set forth by the 1952 National Television Standards
Committee.
They define a method for encoding information into the electronic signal that
ultimately creates a television picture. A single frame of video is made up of 525
horizontal scan lines drawn onto the inside face of a phosphor-coated picture tube
every 30th of a second by a fast-moving electron beam.
The drawing occurs so fast that your eye perceives the image as stable. The electron
beam actually makes two passes as it draws a single video frame, first laying down all
the odd-numbered lines, then all the even-numbered lines. Each of these passes
(which happen at a rate of 60 per second, or 60 Hz) paints a field, and the two fields
are combined to create a single frame at a rate of 30 frames per second (fps).
This process of building a single frame from two fields is called interlacing, a
technique that helps to prevent flicker on television screens. Modern TV sets and
computer monitors use progressive-scan technology, and draw the lines of an entire
frame in a single pass, without interlacing them and without flicker.
Phase Alternate Line (PAL)
The Phase Alternate Line (PAL) system is used in Kenya, United Kingdom, Western
Europe, Australia, South Africa, China, and parts of South America. In short most
countries that were colonized by the British use PAL.
PAL increases the screen resolution to 625 horizontal lines, but slows the scan
rate to 25 frames per second. Frame rate of 1/50th of a second to draw (50 Hz).
Sequential Color and Memory (SECAM)
The Sequential Color and Memory is used in France, Eastern Europe, the former
USSR, and a few other African countries colonized by France. Although SECAM is a
625-line, 50 Hz system, it differs greatly from both the NTSC and the PAL color
systems in its basic technology and broadcast method. TV sets sold in Europe and
Africa utilize dual components and can handle both PAL and SECAM systems.
NB: With the migration from Analogue Broadcasting to Digital Broadcasting these
systems are not in use and can only apply to video production but again the
modern TV sets come with choices between the three systems
Distribution of Television System
Resolution
Resolution defines the number of pixels (dots) that make up the picture on your
television. For any given screen size, the more dots in the picture, the higher the
resolution and the higher the overall quality of the picture.
TV resolution is often stated as the number of pixels or dots contained vertically in
the picture. Each of these resolutions also has a name associated with it.
Standard Definition(SD)
SD (Standard Definition) video specifies the video and audio codecs and file format
that allows users to watch video on several electronic devices built to SD standards.
SD video supports different formats H.264, MPEG-4 and MPEG-2. Standard definition
has always been a 4:3 aspect ratio with a resolution of 640 × 480 pixels (480i or 480p)
Resolution
High Definition (HD)
HD (High Definition) video is video of higher resolution and quality compared to SD
(Standard Definition).
There is no standardized definition for HD, usually any video image with substantially
more than 480 horizontal lines is considered high definition. Normally, HD video has a
resolution of 1280 x 720p whereas FHD (Full High Definition) video has 1920 x 1080p
(1080i or 1080p)resolution.
New technology has given birth to more HD like the UHD(4K). All use the modern
aspect ratio of 16:9.
Ultra High Definition (UHD)-4K & 8K
Ultra high definition is a display resolution standard of at least 3840 by 2160 pixels,
3840 by 2160 is only the floor value, and resolutions being put on various screens
range from this size up to 4096 by 3112 for 4K and up to 7680 by 4320 for 8K. The
Consumer Electronics Association (CEA) clarified in October of 2012 that UHD would
refer to any display with a 16:9 aspect ratio and a minimum of 3840-by-2160 pixel
resolution.
Aspect Ratio
Closely tied to resolution is Aspect Ratio. This is the ratio of width to height of the TV
screen. Certain aspect ratios are designed to handle certain resolutions without any
stretching or distortion of the picture and without any blank space around the
picture.
The most common aspect ratio is 16:9, however depending on the quality of your
video you can choose any.
9:16 (vertical video, as on our phones; Facebook, Instagram, and Snapchat stories)
4:3 (TV, film, and camcorder/video camera recordings back in ’80s and ’90s)
1:1 (a perfect square; the aspect ratio for Instagram or Facebook video)
21:9 or 2.4:1 (ultra-widescreen or anamorphic aspect ratio; mostly used in film to
create a cinematic feel)