Faculty of Engineering
Department of Electrical and Computer Engineering
Title: Digital Television
Mohammed A. Al-Sahafi
Dr. Ali Al-Zahrani
Table of Contents
3. Standards of Broadcasting
6. Receiving Digital signal
7. Protection Parameters
8. Analog TV vs. Digital TV
Digital television is a modern innovation that uses digital data represented in binary digits (0, 1), which can deliver picture and sound information with high performance, even though with less amount of power. On the other hand, earlier technology of digital television is analog television that operates by sending and receiving analog signals, that was not enough to ensure reaching signals clearly without error or distortion. Since the color television in 1950s, digital television was the most important advance innovation.
The greater resolution of digital television in displaying compact pictures and sounds such in HDTV, displaying clarity screen more than analog television. Data sets of digital television is obtained by smaller radio spectrum space which makes it the economical use of the bandwidth and sending more channels data for the same bandwidth. Digital television provides more features than analog television.
3. Standards of Broadcasting
4. Formats and Bandwidth
One of several different HDTV formats that can be transmitted over DTV is: 1280 ? 720 pixels in progressive scan mode (abbreviated 720p) or 1920 ? 1080 pixels in interlaced video mode (1080i). Each of these uses a 16:9 aspect ratio. HDTV cannot be transmitted over analog television channels because of channel capacity issues.
SDTV, by comparison, may use one of several different formats taking the form of various aspect ratios depending on the technology used in the country of broadcast. In terms of rectangular pixels, NTSC countries can deliver a 640 ? 480 resolution in 4:3 and 854 ? 480 in 16:9, while PAL can give 768 ? 576 in 4:3 and 1024 ? 576 in 16:9. However, broadcasters may choose to reduce these resolutions to reduce bit rate (e.g., many DVB-T channels in the United Kingdom use a horizontal resolution of 544 or 704 pixels per line).
Each commercial broadcasting terrestrial television DTV channel in North America is permitted to be broadcast at a bit rate up to 19 megabits per second. However, the broadcaster does not need to use this entire bandwidth for just one broadcast channel. Instead the broadcast can use the channel to include PSIP and can also subdivide across several video subchannels (a.k.a. feeds) of varying quality and compression rates, including non-video datacasting services that allow one-way high-bit-rate streaming of data to computers like National Data cast.
A broadcaster may opt to use a standard-definition (SDTV) digital signal instead of an HDTV signal, because current convention allows the bandwidth of a DTV channel (or “multiplex”) to be subdivided into multiple digital subchannels, (like what most FM radio stations offer with HD Radio), providing multiple feeds of entirely different television programming on the same channel. This ability to provide either a single HDTV feed or multiple lower-resolution feeds is often referred to as distributing one’s “bit budget” or multicasting. This can sometimes be arranged automatically, using a statistical multiplexer (or “stat-mux”). With some implementations, image resolution may be less directly limited by bandwidth; for example in DVB-T, broadcasters can choose from several different modulation schemes, giving them the option to reduce the transmission bit rate and make reception easier for more distant or mobile viewers.
5. Receiving Digital signal
6. Protection Parameters
7. Analog TV vs. Digital TV
Digital television provides more features than analog television, digital channels take up less bandwidth, this means his means that digital broadcasters can provide more digital channels in the same space, provide high-definition television service, or provide other non-television services such as multimedia or interactivity. Analog television common problems with include ghosting of images, weak signals received with noise, and many other problems which decrease the quality of the image and sound, although the program material may still be watchable. With digital television, the audio and video must be synchronized digitally, so reception of the digital signal must be very nearly complete; otherwise, neither audio nor video will be usable.