PCM-TV SYSTEM USING A UNIQUE WORD FOR HORIZONTAL TIME SYNCHRONIZATION

摘要

In a communication system for transmitting and receiving television information by means of digital codes, the horizontal sync pulses are transformed into a code word, thus leaving time slots in the transmitted waveform which are unoccupied by the digital picture information or the code word representing horizontal synchronization. These time slits are used to transmit additional information such as multiple sound or data channels, or bandwidth compression information. In the case of multiple sound or data channels, the channels are multiplexed and coded and transmitted during the available time slots at a bit rate which is the same as the digital picture information bit rate. In the case of bandwidth compression, an address code word is annexed to the single horizontal synchronization code word to provide an address for each line of picture information in a television frame. With all lines identified by addresses, the system compares each line of picture information with a prior line of picture information having the same address and transmits to the receiver only those lines which represent changes of a certain degree from a prior frame. As a result, redundant picture information is not transmitted thereby reducing the total amount of information transmitted, allowing the transmitter to operate at a reduced bit rate. The receiver stores all lines of information and the storage is up-dated by the received non-redundant lines of picture information. During each frame period, the receiver extracts from storage the redundant lines necessary to complete a picture frame.