bandwidth required by a digital television example! (Two transmission channels totaling 12 MHz signal is approximately one-half the number of picture are allocated for terrestrial HDTV transmissions.) It is elements (pixels) displayed per second. The analog video clear from this example that terrestrial television monitor pixel size in the vertical dimension is the distance broadcast systems have to use digital transmission and between scanning lines, and the horizontal dimension is digital video compression to achieve the overall bit rate the distance the scanning spot moves during 1/2 cycle of reduction and image quality required for HDTV signals. the highest video signal transmission frequency. The video The example not only points out the significant system signal bandwidth is given by Eq. (7.4.3), bandwidth requirements for digital video information, but also indirectly brings up the issue of digital video Bw = (cycles/frame)(Fr) quality requirements. The tradeoff between bit rate and = (cycles/line)(N1)(FR) quality or distortion is a fundamental issue facing the (0.5)(aspect ratio)(FR)(N1)(RH) (7.4.3) design of video compression systems. To this end, it is important to fully characterize an application's video communications requirements before designing or = (0.8)(FR)(N1)(RH) selecting an appropriate video compression system. where Factors that should be considered in the design and selection of a video compression system include the Bw = video signal system bandwidth following items: FR = number of frames transmitted per second (fps) NL = number of scanning lines per frame Video characteristics - Video parameters such as the RH = horizontal resolution (lines), proportional to dynamic range, source statistics, pixel resolution, and pixel resolution noise content can affect the performance of the compression system. The NTSC picture aspect ratio is 4/3, the constant 0.5 Transmission requirements - Transmission bit rate is the ratio of the number of cycles to the number of requirements determine the power of