Multiplexed Analogue Components

Abstract: The UNICODEC, developed under the INTELSAT R & D Program, is a TV codec which can transmit and receive any standard signal of NTSC, PAL, or SECAM, by using 15 Mb/s or 30 Mb/s transmission rates (switchable) with two high quality sound channels and one voice circuit. These rates include rate 239/255 BCH FEC for video information. The codec uses the 4:2:2 digital interface for component coding based on CCIR Recommendation 601. The UNICODEC can provide the flexibility to deal with the composite coding now needed in mixed analogue/digital networks, but can also handle either composite NTSC, PAL, SECAM or MAC (multiplexed analogue components), or digital component signals (Y, R-Y, B-Y) in the future. The key technique used here is called MAP (median adaptive prediction) coding, which is one of the adaptive DPCM methods for accurate and simple control in high quality TV transmission; one prediction out of three (interframe, intrafield or interfield) is transmitted without the need for many control bits. There is also a refresh mode for burst error or synchronization recovery. The UNICODEC is expected to provide double capacity with higher quality pictures compared to conventional analogue transmission (FM in 18 MHz). Alternatively, smaller size antennas may be used. This paper describes the objectives of the development of the UNICODEC, its main features and results of field tests.

Abstract: The United Kingdom is about to enter a new and exciting phase of its broadcasting history. On 27th August 1989 a satellite was launched for the world's first high-power direct broadcasting by satellite (DBS) service which is funded entirely privately. For the success of this service the broadcaster needs to establish a large customer-base quickly and yet needs to offer the potential of receiver improvements for the future. Against this background the D-MAC/packet system has been adopted as the signal format to be used. This system offers a reception option involving a relatively inexpensive set-top convertor and yet it also provides a number of important options for enhancing the service. The paper briefly describes the D-MAC transmission system and highlights in particular how it can provide an evolution to high-definition television (HDTV) in the future.

Abstract: During 1986, the South African Broadcasting Corporation (SABC) implemented a system for distributing its TVI program and various radio programs via a leased transponder on an Intelsat satellite to distant terrestrial transmitting stations for rebroadcasting purposes. The system and its performance are described. A brief description of the B-MAC (B version of the multiplexed analogue components system) coding format is included. Problems experienced during the first two years of operation and the solutions applied are discussed, as well as the overall successes of the system. Problems considered are: the potential existence of interference from terrestrial microwave links, rain attenuation, lightning damage to equipment, synchronization problems between B-MAC and asynchronous video signals, cross polarization effects, and satellite tracking/stationkeeping. >