ITU-R REPORT BS.795-3 PDF

Introduction

High quality multi-channel sound has been .shown to be an asset to television programme transmissions for stereophonic sound reproduction and for separate sound channels. Studies conducted since 1959 have led to the development of several different methods of adding additional sound channels and data transmissions to television systems in use throughout the world. Some of these systems have been implemented with two being recommended, see Recommendation 707 and two being proposed in Appendices I and II to Annex I to this report.

A system for transmission of stereophonic or two separate sound signals using two sound carriers, "the two-sound carrier FM system", is in regular service as described in section 3. This service began in the Federal Republic of Germany in 1981 and has also been introduced in other countries, e.g. Australia, Italy, Netherlands and in the Republic of Korea.

The NICAM-728 digital system, where multi-channel sound and data are carried on a-digitally modulated carrier additional to the analogue sound carrier has been studied in the United Kingdom and a number of other countries, and by the EBU. This system was put into regular service in Denmark, Finland and Sweden in 1988 and in New Zealand and the United Kingdom in 1989. The system is described in section 4. Studies are proceeding in France on the adoption of the digital system to television system L [CCIR, 1986-90a].

In 1978, an FM-FM system of multiplexing two sound channels on the single sound carrier of television system M was put into service in Japan. Stereophonic sound or two separate sound channels may be provided by this system as described in section 5. Work is under way to implement data services, for example facsimile broadcasting to provide additional text services.

In North America, the United States and Canada have implemented the BTSC* FM-AM multiplex system of multi-channel sound with television broadcasting beginning in 1984. The BTSC system permits the simultaneous transmission of stereophonic sound, an additional monophonic sound programme (second audio programme or "SAP") service, and a narrowband or data channel for station operation purposes. At this time, the BTSC system as described in section 6 is preferred for use in the United States but improved systems are possible.

* Broadcast Television Systems Committee of the Electronic Industries Association, which adopted this system after five years of study.