 Hello friends, myself Mr. Elia Archanane, assistant professor from Department of Electronics, Walshchand Institute of Technology, Solapur. Today we are going to see the topic digital television system from the subject audio-video systems. So basically, what are the learning outcomes from this topic at the end of this topic? Digital television systems are able to introduce regarding modifications in standard television systems. Also they can understand the working principle of digital TV broadcasting system. So why digital television? So initially there were analog television systems, but why we are choosing or why we are going towards digital television, hence what is digital television? So digital television is nothing but it refers to digital representation and processing of the signal as well as its digital transmission, digital presentation and processing that may be of image, video or sound. Digital television broadcast involves converting image and sound into digital code, the digitization of images and sound or data starts with compression in order to minimize the capacity required for transmission channel. That means here minimum capacity it is analogous to the required bandwidth which is used for transmitting of these data through a transmission channel. Television is performed to the industry standard which is known as MPEG-2 that is moving pictures evolution group version 2. Then modulation takes place whereby the code is formatted for propagation along terrestrial satellite or cable media. That means your propagation can take place for digital broadcasting, satellite broadcasting or cable broadcasting. The digital television transmission uses digital processing and compression to achieve simultaneous transmission and reception of different programs. That means here digital television generally uses different processes algorithms or compression algorithms which are used for transmission and reception of different programs. In any event the quality of the signal received is equivalent to the studio output that means here the quality which we are receiving from a particular transmitted area the quality remains same as that of the studio output that means adds that of real time output. So why we are going towards digitalization? Basically here as we move towards digitalization in television here the basic thing is that better quality that is higher resolution can be obtained even for weak signals that means here weak signals can be converted into high quality picture or sound parameters. Digital signal consists of binary pulse train that can be made immune to amplitude degradation by regeneration of pulses. Digital signals here generally the sound or pictures are converted into binary train of pulses these pulses these pulses amplitude are degraded due to the noise which occurs or which interferes during the channel or in the channel. This can be overcome by regeneration of the pulses. Audio and sound quality improves digital data is easy to store delay and transmit and easy to manipulate that is conversion into NTSC PAL NTSC or PAL standards. So what are the different digital standards which are used for televisions? First is ATSC that is advanced television system committee which is basically is used in North America ISDBT integrated service digital broadcast which is nowadays generally used in Japan and Brazil DVBT which includes digital video broadcasting which is used in Europe, Russia, Australia and India. In digital television systems the only difference is in between NTSC and PAL in which the scanning process is of scanning process is different for these two standards that is for NTSC and PAL the scanning process is different. So we are now going to see the block diagram of digital television. So this is the block diagram for digital television here the digital in digital television this block diagram is divided into two basic parts that is this part is of the transmission part from here to here and from the down converter to this part this is the receiving part for digital television. So basically the video audio and data these are encoded initially so video is encoded by video encoder audio is encoded by audio encoder and data is directly these all three are given as input to a MUX. The MUX gives the output to the transport formata where the video audio and data are converted into digital one and then these are given to FEAC encoder then the modulator up converter and then the channel. This channel is generally used for transmission and reception of the digital television signals at the same time. So the receiver generally includes channel, down converter, demodulator, FEC decoder, transport, deformator, demux and then it is given to video decoder, audio decoder and the data itself. So this is the part for the receiver and the upper part is for the transmitter which are used for digital television broadcasting. So here the explanation of digital television block diagram is the video audio and other services that is data are compressed and multiplexed to a particular streams. These streams are again multiplexed with the source data to form other format like MPEG2 that means the multiplex data is given to the source formata where the stream of data is again converted into a format which is known as MPEG2. The FEC encoder prevents error which are caused due to noise and other interface channel. FEC generally uses algorithm like read Solomon coding, outer interleaving and convolution coding for the error detection and error detection and correction purpose. The modulator then converts the FEC protected transport packets into digital symbols that means FEC protected transport that means here the data is converted into a particular coded information. Then these involves generally the modulator involves or the modulation types which are used for digital TV transmission are QAM, OFDM in DVBT that is orthogonal frequency division multiplexing, QAM quadrature amplitude multiplexing, ISDBT systems or PAM and VSB in ATSC. Here as you can see as the television standard changes so the modulation technique also changes for that particular standard. The final stage is the upper converter which converts the modulated digital signal into the appropriate RF channel. These the sequence of operation in the receiver side is a reverse order of the operation in the transmitter side as we have seen in the block diagram the receiver block diagram start from channel then it goes to the down converter and so on. So these are the references for the digital television system, satellite communication third edition by Dennis Roddy. Next composite satellite and cable television systems by R. R. Gulati and digital television broadcasting by Dr. Vijay Anand Patnaik it is a research paper from IIT Bhubnishwar. Thank you for watching the video.