THE GRAND ALLIANCE SYSTEM FOR US HDTV

The US HDTV process has fostered substantial research and development activity over the last several years. The Advisory Committee on Advanc ed Television Service (ACATS) was formed to advise the FCC on the tech nology and systems suitable for delivery of High Definition Service ov er terrestrial broadcast channels. Four digital HDTV systems where tes ted at the Advanced Television Testing Center. All the systems gave ex cellent performance, but the results were inconclusive and a plan for a second round of tests was prepared. As each of the four systems wher e being readied for retest, the proponents of the four individual digi tal HDTV proposals worked together to define a single HDTV system whic h incorporated the best technology from the individual systems. The co nsortium of companies, called the Grand Alliance (GA), announced a com bined system and submitted it to ACATS for consideration. After ACATS certification, the GA began construction of a prototype system to subm it for laboratory testing at the end of 1994. This paper describes the video compression subsystem and the hardware prototype. The preproces sing, motion estimation, quantization, and rate control subsystems are described. The system uses bidirectional motion compensation, discret e cosine transform, quantization and Huffman coding. The resulting bit stream is input into a Transport system which uses fixed length packet s. The multiplexed transport stream is input into the 8-VSB transmissi on system. Finally, the specifics of the hardware implementation are d escribed and some simulation results are presented.