Teletext data change detection and noiseless data compression

The full channel teletext system is a high speed data broadcasting system. Pages of information are broadcast in a cyclic manner. The detection of data change in the information pages is necessary for data analysis, database update and retransmission. Lossless data compression is also necessary to enhance the data throughput in rebroadcasting and to reduce the storage requirement. Performing data change detection and data compression in real time using a software approach in a small machine is impossible for such high speed data. The authors describe the algorithms that are suitable for hardware implementation for both data change detection and noiseless data compression. They also illustrate the use of cyclic redundancy check (CRC) and dictionary based compression scheme using a hashing function to detect changes and compression respectively in the teletext pages