High definition TV broadcast formats

When HDTV systems started developing in the early 1980s, fully-digital coding and modulation systems were too sophisticated to implement as consumer technology, and furthermore such systems were in a relatively early state of development. Thus systems were developed, based largely on analogue signal transmission ideas, where the signal transmitted was basically an analogue representation of the video signal. Such systems are forced to allocate the available transmission bandwidth equally across the picture, maintaining a uniform sample density, since the samples are transmitted in an analogue form in a conventional raster. However, such systems do offer a significant degree of freedom in selecting how the image is filtered prior to sampling, and how the samples are arranged. Two such systems, MUSE and HD-MAC, were devised; at present these remain the only fully-developed HDTV broadcast formats. This paper describes these systems.