devel/rscode 1.0 NetBSD

The Reed-Solomon Code is an algebraic code belonging to the class of BCH (Bose-Chaudry-Hocquehen) multiple burst correcting cyclic codes. The Reed Solomon code operates on bytes of fixed length.

Given m parity bytes, a Reed-Solomon code can correct up to m byte errors in known positions (erasures), or detect and correct up to m/2 byte errors in unknown positions.

This is an implementation of a Reed-Solomon code with 8 bit bytes, and a configurable number of parity bytes. The maximum sequence length (codeword) that can be generated is 255 bytes, including parity bytes. In practice, shorter sequences are used.

The more general error-location algorithm is the Berlekamp-Massey algorithm, which will locate up to four errors, by iteratively solving for the error-locator polynomial. The Modified Berlekamp Massey algorithm takes as initial conditions any known suspicious bytes (erasure flags) which you may have (such as might be flagged by a laser demodulator, or deduced from a failure in a cross-interleaved block code row or column).

Once the location of errors is known, error correction is done using the error-evaluator polynomial.