Decoder for the decoding of code words which are blockwise protected against the occurrence of a plurality of symbol errors within a block by means of a reed-solomon code, and reading device for optically readable record carriers

摘要

A decoding system for code words which are protected against the occurrence of a plurality of symbol errors within a code word by means of a Reed-Solomon code. After the formation of the syndrome symbols, the key equation is solved, assuming the least possible number of symbol errors. When a plausible number L is found using 2L syndrome symbols, an additional number of syndrome symbols is considered for determining the discrepancy quantity. The locator equation is directly solved when it is of a low order. For a higher order, a Chien search cycle is performed and any symbol error found is removed by division until the order becomes low enough for direct solution. The decoding system is suitable for implementation by means of a microcomputer and for use in a reading device for optically readable record carriers.