A number of Television standards now coexist the worldwide. It also offers detail listings of standards prevalent in various countries.Television broadcast commenced approximately 50 years ago. The knowledge gained over the years has helped evolve better standards. As result of this, US which saw the birth of wide spread commercial television broadcasts, evolved the first system which predictably, is also the most primitive. Subsequent television systems have learnt from earlier mistakes.
Before we consider different television systems, we need to take a look at the basics of television transmissions. A television transmission consist of a series of rapidly changing pictures which convey to the viewer, an illusion of continuous motion. The pictures need to flash at a rate of more than 16 pictures per second, to fool the eye into seeing continuous motion. Each of these rapidly changing pictures is termed as a “frame”. Typically a television transmission consists of either 25 or 30 frames per second.
Each picture consists of several closely spaced lines. The lines are scanned (written) from left to right and from the top of the screen to the bottom of the screen. Typically a TV picture consists of 525 or 625 lines. In view of the large number of lines, if all lines were written one after the other on the screen, the picture would begin to fade at the top of the screen by the time the last few lines at the bottom of the screen are written. To avoid this, the first frame carries only the odd numbered lines e.g. line numbers 1, 3, 5 etc. The next frame carries only even numbered lines e.g. line numbers 2, 4, 6 etc. In this manner, successive frames carry the odd and even numbered lines.
Analogue Terrestrial Television (Existing)
•Analogue Television signals received via the aerial or communal aerialbroadcast distribution (CABD)system for viewing on Television set
•Currently four free-to-air Television programme channels in HK
Digital Terrestrial Television (Coming)
•Digital Television signal received via aerial or CABD system anddecodedfor viewing on Television set
•Supports more free-to-air Television programme channels plus high definition .
Introduction to Broadcast Television Channel :
In the last 50 years, the television industry has seen distribution expand from terrestrial
broadcasting to cable and satellite. Now, we are into the age of the Internet. As the base of broadband users reaches 450 million worldwide, having your Television channel online is essential to retain the loyalty of your existing viewers and to expand your reach to a broader audience. But streaming via Content Delivery Networks (CDNs) is expensive – with no effective way to recoup the costs or monetize your channel. In today’s financial environment where positive ROI is a critical success metric, traditional Internet
streaming is cost-prohibitive and not an option.
Q1:What are the Benefits of DTT
Ans: Benefits DTT:
Improved the reception andthe picture quality Support new services like high definition television (HDTV) and multimedia / interactive services Carry more contents in one channel Support mobile / portable reception Better use of frequency spectrum Release valuable frequency spectrum for other uses after full migration from analogue to digital broadcasting.
Q2: What is the name of INTERNATIONAL TELEVISION STANDARDS of Afghanistan?
Ans: of INTERNATIONAL TELEVISION STANDARDS of Afghanistan is PAL/SECAM H.
Q3: What is PAL?
This hue change problem is caused by shifts in the colour sub-carrier phase of the signal. A
modified version of the NTSC soon appeared which differed mainly in that sub-carrier phase was
reversed on each second line.
Q4: What are the advantages of NTSC/525 ?
Ans: NTSC/525 Advantages:
Higher Frame Rate – Use of 30 frames per second (really 29.97) reduces visible flicker. Atomic
Colour Edits – With NTSC it is possible to edit at any 4 field boundary point without disturbing the
colour signal. Less inherent picture noise – Almost all pieces of video equipment achieve better
signal to noise characteristics in the NTSC/525 form than in their PAL/625.
Q5: What are the advantages of SECAM/625 ?
Ans: SECAM/625 Advantages:
Stable Hues and Constant Saturation – SECAM shares with PAL the ability to render images with
the correct hue, and goes a step further in ensuring consistent saturation of the colour as well. Higher
the Number of Scan Lines – SECAM shares with the PAL/625, higher number of scan lines than