News that the US Federal Communications Commission’s Advisory Committee on Advanced Television Service, is now to review a single digital high definition television standard proposed by a a Grand Alliance of all four contending consortia is raising hopes that by mid-decade, all the key technologies and infrastructures will be in place for a full-scale merging of television and computer technology. Important aspects of the Grand Alliance technical proposal include the replacement of the present interlaced scanning technique, where two scans of the screen make up each frame, to progressive scan transmission, where entire picture frames are transmitted sequentially, and the use of so-called square pixels, where the dots on a television screen are arranged in equally spaced rows and columns. Both these design aspects are important for the interoperability of television with computers, telecommunications and other media and applications. Interlaced scan transmission used today would be accommodated in the initial deployment of the system so as not to obsolete current sets too quickly. The proponents agree that all large-screen receivers – 34 and up – will incorporate a 60 frame per second 787.5 line or higher progressive scan display mode, while progressive display would initially be optional for smaller screen sets. It was agreed that all transmission of film material will be in a progressive scan format from launch of services. And all partners endorse the objective of migrating the standard to in excess of 1,000 lines progressive scan transmission, and will work together to eliminate interlaced scanning format from the transmission path in the future. To handle multiple transmission formats, the merged system will use source-adaptive processing – so that the set will handle the signal appropriately according to its type. The merged system also will feature a prioritised, packetised data transport structure. One dissenter is the Massachusetts Institute of Technology, which maintains that a standard using progressive scan transmission only from the start would be best.
