subsystems: 1. Source coding and compression 2. Service multiplex and transport 3. RF/transmission subsystem Of course, source coding and compression refers to bit rate reduction methods (data compression), which are appropriate for the video, audio, and ancillary digital data bit Video subsystem Service multiplex and transport RF/transmission system Video Video source catalog and compression Channel Transport Audio subsystem coding Audio Audio Service source catalog and compression multiplex Modulation Ancillary data Control data Receiver characteristics Figure 16.7 Block diagram of the digital terrestrial television broadcasting model. (Based on the ITU-R Task Group 11.3 model. From Ref. 18, Figure 4.1. Reprinted with permission.) The reader will recall that the conventional 525-line NTSC television signal, when radiated, is assigned a 6-MHz channel. See Figure 16.6. 16.9 DIGITAL TELEVISION streams. The ancillary data include control data, conditional access control data, and data associated with the program audio and video services, such as closed captioning. Ancillary data can also refer to independent program services. The digital television system uses MPEG-2 video stream syntax for coding of the video and Digital Audio Compression Standard, called AC-3, for the coding of the audio. Service multiplex and transport refers to dividing the bit stream into packets of infor- mation, the unique identification of each packet or packet type, and appropriate methods of multiplexing video bit stream packets, audio bit stream packets, and ancillary data bit stream packets into a single data stream. A prime consideration in the system trans- port design was interoperability among the digital media, such as terrestrial broadcasting, cable distribution, satellite distribution, recording media, and computer interfaces. MPEG- 2 transport stream syntax was developed for applications where channel bandwidth is limited and the requirement for efficient channel transport was overriding. Another aspect of the design was interop