erability with ATM transport systems (see Chapter 18). RF/transmission deals with channel coding and modulation. The input to the channel coder is the multiplexed data stream from the service multiplex unit. The coder adds overhead to be used by the far-end receiver to reconstruct the data from the received signal. At the receiver we can expect that this signal has been corrupted by channel impairments. The resulting bit stream out of the coder modulates the transmitted signal. One of two modes can be used by the modulator: 8-VSB for the terrestrial broadcast mode and 16-VSB for the high data rate mode. 16.9.4.1 Video Compression. The ATSC standard is based on a specific subset of MPEG-2 algorithmic elements and supports its Main Profile. The Main Profile includes (a) three types of frames for prediction (I-frames, P-frames, and B-frames) and (b) organization of luminance and chrominance samples (designated 4 : 2:0) within the frame. The Main Profile is limited to compressed data of no more than 80 Mbps. Figure 16.8 is a simplified block diagram of signal flow for the ATSC system. Video elementary Transport VSB RF stream packets transmission Source Video Transport Transmission video encoder subsystem subsystem Video Channel subsystem Receiver Receiver Reconstructed Video decoder transport transmission video subsystem subsystem Video Transport VSB RF elementary packets reception stream Figure 16.8 Video coding in relation to the ATSC system. (From Ref. 18, Figure 5.1, reprinted with permission.) TELEVISION TRANSMISSION Table 16.4 ATSC Compression Formats Vertical Lines Pixels Aspect Ratio Picture Rate 60I, 30P, 24P 60P, 30P, 24P 16:9 and 4:3 60P, 60I, 30P, 24P 60P, 60I, 30P, 24P Source: Ref. 18, Table 5.1. (Reprinted with permission.) Video preprocessing converts the analog input signals to digital samples in such a form needed for later compression. The analog input signals are red (R), green (G), and blue (B). Table 16.4 lists the compression formats covered by the ATSC standard. The following explains some of t