rks (ISO/IEC, 1995). MPEG-2 serves a wide range of applications, such as HDTV, digital storage Chapter 3 Digital Video Transmission media, and television broadcasting. It is based on motion-compensated block-based trans- form-coding techniques, with target bitrates between 4 and 9 Mbit/s. It uses intraframe compression to remove redundancy within frames and interframe compression to reduce redundancy contained over sequences of many pictures. An MPEG-2 sequence contains three types of frames, I, P, and B, and supports variable picture sizes; in most cases, the pictures are interlaced. MPEG-2 supports scalability (Ghanbari, 2003) by permitting the division of a continuous video signal into two or more coded bitstreams representing the video at different resolutions, picture qualities, or picture rates. Additional frame buffering is required at the encoder for prediction of B frames. MPEG-3 was originally intended for HDTV, but it was realized that MPEG-2 could modified to accommodate this and SO it was abandoned. MPEG-4 was standardized in 1998 and represented a departure from standard thinking about video in that it attached importance to objects within the image. This allows objects to be mixed together-for example, cartoons and real objects-and support for the Virtual Reality Modeling Language (VRML) was also offered. MPEG-4 added to MPEG-1 and -2 integration of natural and synthetic support for 2D and 3D content and interactivity. Coding is at very low rates and supports management and protection of intellectual property. MPEG-4 is also compatible with major existing standards: MPEG-1, MPEG-2, ITU-T H.263, and VRML. The MPEG-4 standard is very extensive, and some regard the specifica- tion as a "wish list" because it is SO large. Profiles are declared, which define subsets of the standard for individual implementations. The chief difficulty associated with MPEG-4 is the requirement to segment objects from a scene, and consequently MPEG-4 only finds wide- spread use in the "block-based" profile. MPEG-7 was form