Technology: BBC loses the race for stereo television

时间:2019-03-04 09:04:02166网络整理admin

BRITAIN’S Independent Broadcasting Authority is to start transmitting digital stereo sound in September, two years ahead of the BBC, using technology developed by the BBC’s own engineers. Televisions can pick up the new stereo system, called Nicam 728, and video recorders to tape it, are already in the shops. The ITV and Channel 4 programmes expect to win viewers from the BBC because the benefit of hearing music and sport in stereo can be dramatic. Although the BBC broadcasts some unannounced test signals in stereo at the moment, it will not provide a regular stereo service until the autumn of 1991. Japan, the US and West Germany already have stereo television, but their systems are analogue. The IBA’s system converts each sound channel into digital code, and then compresses these codes into 10-bit words. The compression technique is called Near-Instantaneously Companded Audio Multiplex. ‘Companded’ means that the signal is compressed before it is sent then expanded at the receiver. The digital code data runs at 728 kilobits per second, which gives the system its name. The IBA’s engineers face a difficult technical problem. Sound signals are currently squeezed into gaps in the television signal created by the pulses that synchronise the picture. The engineers now have to cram twice as many digital bits into the same spaces. Early tests on the IBA’s new system showed that the digital sound corrupted too easily. But it has ordered new coding equipment from Denmark,