ntrolling VCR-style playback and random-access of bit streams encoded onto digital storage media (e.g., compact disc). Commands include fast forward, advance, still frame and go-to. Part 6 was approved in 1996. Part 7-NON-BACKWARDS COMPATIBLE AUDIO (13838-7). This part extends the two-channel audio of MPEG-1 (11172-3) by adding a new syntax to efficiently decorrelate discrete multi-channel surround sound audio. Part 7 of MPEG-2 was approved in 1997. Part 9- REAL-TIME INTERFACE (RTI) (13838-9). This part defines a syntax for video on demand control signals between set-top boxes and head-end servers. Part 9 was approved as an International Standard in July 1996. MPEG-2 Levels Each MPEG-2 defines "quality classifications" that are known as levels. Levels limit coding parameters (sample rates, frame dimensions, coded bit rates, etc.). The MPEG- 2 levels are as follows: Video Communications: The Whole Picture Level Resolution Frame Pixels Maximum Purpose Sampled bit rate Second 352 X 240 30 fps 3.05 M 4 Mbps Consumer Tape, 740 X 480 30 fps 10.40 M 15 Mbps CCIR-601 Studio 1440 X 30 fps 47.00 M 60 Mbps Commercial 1920 X 30 fps 62.70 M 80 Mbps Production SMPTE Figure Appendix B-3. MPEG-2 Levels The two most popular MPEG-2 levels are the Low (or SIF) Level and the Main (or CCIR-601) Level. MPEG-2 Profiles MPEG-2 consists of six different coding tools that are known as profiles. Profiles are a defined sub-set of the MPEG-2 specification's syntax (algorithms). Different profiles conform to different MPEG-2 levels and are aimed at different applications (high- or regular-definition television broadcasts over different types of networks). Profiles also provide backward compatibility with other specifications such as H.261 or MPEG-1. Simple Spatially 4:2:2 Profile Profile Scalable Scalable Profile Profile Profile Profile Level Level Level Figure Appendix B-4. MPEG-2 Profiles MPEG Family of Specifications The MPEG-2 Video Main Profile conforms to the CCIR-601 studio standard for digital TV, and is implemented widely in MPEG-2 d