Digital Video Recording for Television Broadcasting

Abstract

Videotape recorders have existed since 1956 and over the years have been perfected to the point where they provide a virtually “transparent” storage medium; the average viewer cannot distinguish a taped production from a live one. Nevertheless, the supremacy of these conventional analog VTRs is about to be challenged by rapidly developing digital technology. Digital VTRs, which may be commercially available in the next 5 to 10 years, are expected to provide the advantages of automatic operation and potentially lower operating costs. Multiple generations of programs (copies of copies) may be possible with little or no degradation with digital VTRs. Two major problem areas in the development of digital VTRs are how to reduce the very high bit rate required (presently on the order of 100 megabits/second) and at the same time reduce the error rate to about 1 part in 10 7. Intense efforts are being made to meet these requirements with very efficient encoding and with error correction and detection circuits. It is thought that exotic storage techniques such as laser-beam holography on thermoplastic film will become practical too late to influence the near-term market for digital magnetic VTRs.