Digitol Tv Essay Research Paper Digital Television

Digitol Tv Essay, Research Paper

Digital Television Television is a medium for recording and transferring images and sound from one point to another. The Image portion of the system is a light-To-light system, gathering variations in light at the source via pickup device such as a camera and recreating those variations in light as a visual image via a display device such as cathode ray tube (CRT). Television was initially intended for sports, news and entertainment applications and its now finding application in telecommunications as videoconferencing, for computing as desktop video, for medicine as telemedicine and in education as distance learning, because of this rapid application, digital television gives the development of accurate and detailed picture and sound. Digital Television does not imply digital transmission or reception of some new type of TV signal. The Television set tackle in this term paper receive conventional TV signals and produce corresponding pictures and sound which is superior in conventional Television. Digital Television came into being when ITT developed five Integrated circuit (ICs) that replace virtually all of the circuits between the tuner or what we called channel selector and the picture tube /audio amplifier section found in analog or conventional television set. The five digital ICs replace about 24 analog ICs in conventional television and this ICs are VLSI (Very Large Scale Integration) devices. The key factor to digital television is in analog to digital (A/D) and digital to analog (D/A) conversion. In the simplest terms, the analog signal which is the composite video and sound at the output of television tuner are converted to their digital equivalent by and analog to digital (A/D) process somewhat similar to that found in compact discs. The resultant digital signals are then processed to produce the corresponding video and audio in digital form. When the processing is complete, the digital signals are restored to analog form by digital to analog (D/A) converters and applied to the picture-tube and audio circuits. The analog to digital (A/D) conversion, digital processing, and Digital to analog (D/A) conversion are all take place in the five digital ICs. This term paper are primarily the discussion of digital television system (block diagram), the basic principles in how to the conversion take place, the comparison of both analog television and digital television tackles in research and analysis section and the advantages tackles in finding section. BACKGROUND OF STUDY To understand further the comparison of both digital and analog television and there advantage listed in finding section of this term paper. Let as first tackle the digital television system, this included parts of Analog to digital and digital to analog conversion and the THE DIGITAL TELEVISION SYSTEM basic digital conversion and storage concept. FIGURE 1 DIGITAL TELEVISION SYSTEM CRT Figure 1, show the digital television system which consist of image source or a image you want to capture, a means such as a camera of converting the image into analog electronic signal , a mean of transforming the analog signal into a digital signal ( analog to digital converter or A/D), some process(PD) which is applied to the digital signal, a means of re-transforming the resulting digital signal back to the analog domain (digital to analog converter or D/A) and means such as a display of reconverting the analog signal back into light for the benefit of the observer. The digital process varies according to the application. It can be a variable time delay used for frame synchronization and time base correction a video processor that correct for luminance and chrominance error, an image manipulator that permits digitally generated effects and graphics to be added to the image a data-compression scheme to reduce the amount of data or simply a transmission path. ANTIALISING SAMPLE & QUNTIZING ENCODER FILTER HOLD LEVEL SELECTION fs FIGURE 2 THE A/D CONVERTER INPUT DECODER SAMPLING RECONTRUCTION REGISTER fr FILTER FIGURE 3 D/A CONVERTER The A/D converter a show in the figure 2 consist of four basic component s, a band-limiting, antialiasing filter. a sample- and-hold circuit (S&H) that samples the analog signal, the quantizing unit (Q) that divide the range of each analog signal sample into Q distinct levels, and finally an encoder (ENC) that placea a specified code on the output data line (Do-Dn) for each of the Q level. The D/A converter (see the figure 3) consist of four basic component, a digital input register (REG) in which the bits of the world to be converted are stored for one time period, a decoder (DEC) that converts the data lines into Q distinct analog levels, a resampling (Rc)circuit that correct for distortions due to the digital sample and hold process, and a band-liming, restoration or reconstruction filter (FD). BASIC DIGITAL CONVERSION AND STORAGE CONCEPTS Special effect (as the advantage listed in finding section) like preview mode, freeze mode, editing mode and finally the picture in picture mode, are made possible by converting the conventional analog video signal at the tuner output to a digital format of data bits. These data bits are stored in the memory as is done with computers. Later, the date bits are read from memory and changed back to an analog signal that produces the desired special effect pictures. FIGURE 4 BASIC DIGTAL CONVERSION/STORAGE Figure 4A, illustrat