SAMPLE & QUNTIZING ENCODERFILTER HOLD LEVEL SELECTION fs FIGURE 2 THE A/D CONVERTER INPUT DECODER SAMPLING RECONTRUCTION REGISTER fr FILTERFIGURE 3 D/A CONVERTERThe 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 places 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 CONCEPTSSpecial 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/STORAGEFigure 4A, illustrates an original analog video signal for one horizontal line. Figure 4B, show how the analog level of the signal is sampled many times at regular intervals. Figure 4C, shows the video signal reconstr...
