d on the color subcarrier frequency called fsc. For NTSC television the color subcarrier is at 3.58 MHz. In some cases the sampling rate is three times this frequency (3fsc), in other cases four times the color subcarrier fre- quency (4fsc). For PAL television, the color subcarrier is 4.43 MHz. Based on 8-bit PCM words, the bit rates are 3 X 3.58 X 106 X 8 = 85.92 Mbps and 4 X 3.58 X 106 X 8 = 114.56 Mbps. In the case of PAL transmission system using 4fsc, the uncompressed bit rate for the video is 4 X 4.43 X 106 X 8 = 141.76 Mbps. These values are for com- posite coding. In the case of component coding there are two separate digital channels. The luminance channel is 108 Mbps and the color-difference channel is 54 Mbps (for both NTSC and PAL systems). In any case, linear quantization is employed, and an S/D (signal-to-distortion ratio) of better than 48 dB can be achieved with 8-bit coding. The coding is pure binary or two's complement encoding. 16.9.3 Bit Rate Reduction - Compression Techniques In Section 16.9.2 raw video transmitted in a digital format required from 82 to 162 Mbps per video channel (no audio). Leaving aside studio-to-transmitter links (STL) and CATV supertrunks, it is incumbent on the transmission engineer to reduce these bit rates without sacrificing picture quality if there is any long-distance requirements involved. CCIR Rep. 646-4 (Ref. 14) covers three basic bit rate reduction methods: Removal of horizontal and vertical blanking intervals Reduction of sampling frequency Reduction of the number of bits per sample. We will only cover this last method. 16.9 DIGITAL TELEVISION 16.9.3.1 Reduction of the Number of Bits per Sample. There are three methods that may be employed for bit rate deduction of digital television by reducing the number of bits per sample. These may be used singly or in combination: Predictive coding, sometimes called differential PCM Entropy coding Transform coding Differential PCM, according to CCIR, has SO far emerged as the most popular method. The prediction process r