ecoder chips and in direct broadcast satellite. It will also be used for the delivery of video programming over cable television. It is targeted at a higher encoded bit rate of less than 15Mbps and specifies a resolution of 720x480 at 30 fps, allowing for much higher quality than is typical with MPEG-1. It supports the coding parameters as set forth in MPEG-2's high, high 1440, main and low levels. It uses the 4:2:0 chroma format. The Video Main Profile also supports I, P, and B frames. The U.S. ATSC Digital Television Standard (Document A/53-HDTV) specifies MPEG-2 Video Mail Profile compression. The Simple Profile is nothing more than the Main profile without B frames. As we said earlier, B frames require a set-top or other MPEG decoder to have a certain amount of integrated circuit (IC) memory; that becomes too costly for some applications. The SNR Scalable and Spatially Scalable Profiles are very complex and are useful primarily for academic research. Scalability allows a decoder to divide a continuous video signal into two or more coded bitstreams that represent the video at different resolutions (spatial scalability) or picture quality (SNR scalability). Video is also scalable across time (temporal scalability). Equipment manufacturers do not generally pursue scalable profiles. They require twice as many integrated circuits as non-scalable profiles, which approximately double their cost. The High Profile is aimed at high-resolution video. It supports chroma formats of 4:2:2 and 4:2:0, resolutions that range between 576 lines by 720 pixels and 1152 lines by 1920 pixels, and data transfer rates of between 20 and 100 Mbps. It also supports I, P, and B frames. The 4:2:2 Profile (that was added to MPEG-2 Video in January of 1996) possesses unique characteristics more desirable in the professional broadcast studio and post- production environment. The 4:2:2 Profile uses a chroma format of 4:2:2 (or 4:2:0), uses separate luminance and chrominance quantization tables, allows an unconstrained number of bits in a macr