on Systems Committee has existed and continues to exist for the purpose of developing and maintaining digital television standards. APPENDIX PROGRAM CONTENT PAYLOAD SIZE FOR TDM ATM AND IP NETWORK TRANSPORT Defining content or other payload size is critical to efficient use of network transmission facilities. When program content gets trans- ported in non-real time (i.e. not live or pre-recorded, and not "streaming"), it gets moved by moving the physical media it is stored on, or via a network using file transfer protocol (FTP). When program content moves in real time, network bandwidth or connection speed is fixed and must be sufficient to accommodate the payload in terms of bits-per-second. When content moves on physical media or via FTP over a network, speed of movement or bandwidth available in the transport channel can be fixed or variable. This variation is intolerable for real-time content transport, but it is a trade-off against the amount of time it takes to deliver the content. Table 1 contains examples of payload bitrates in megabits per second across a range of selected arbitrary compression ratios. These examples are for real time streaming transport only. Payload may be only the content, or it may include overhead bits to improve end-to-end bits-to-errors ratio (BER) reliability, and/or robustness. The other side of the coin asks: How much bandwidth is available on a given transmission facility? Content transport on TDM facilities is the simplest and easiest to understand. It is also a reference model for ATM and IP transport media performance measurement and assessment. Figure 1 is a block diagram showing the functions making up multiplexing of audio, video, and data as might be encountered when mapping elementary program content streams into a transport stream and then on to a Practical IP and Telecom for Boardcast Engineering and Operations Copyright © 2004 by Fred Huffman. All rights of reproduction in any form reserved. APPENDIX TABLE 1 Payload Speed and Content Transfer Rates High Definition -