R&D Report 1992-12 : Experiments with the HIVITS HDTV contribution codec A.D.R. Cotton, N.D. Wells As more and more programmes are made in high definition television (HDTV) formats, so the need to provide complete production facilities will increase. An important part of television production is the ability to transmit very high quality television signals over long distances for programme contribution purposes. For example, this may be from an outside broadcast unit to a television studio centre or a transatlantic satellite link for a live television interview. The BBC Research Department, in collaboration with Thomson-CSF/LER and TRT, a French subsidiary of Philips, as part of the RACE HIVITS project, has participated in the construction of 140 Mbits/s contribution-quality bit-rate reduction codec for the transmission of digital HDTV. This report describes the codec architecture, some of the problems that have arisen out of the necessity to perform parallel processing, results from buffer regulation optimisation experiments and results from the field trials conducted over satellite links. The architecture of this equipment has been especially developed to allow the generation of an implementation- independent bit stream. The current equipment based on six conventional definition bit-rate reduction codecs working in parallel, will perform equally well with future generations of equipment based on fewer processing units operating in parallel. Indeed, the output bit stream is equivalent to a suitably scaled version of the current ETSI and CMTT standards for the coding of conventional definition television.