Encoding and decoding of runlength limited codes (RLL) with low error propagation

摘要

Methods and apparatuses for encoding and decoding RLL MTR codes such as a rate 16/17 RLL(6) MTR(4) code and a rate 24/25 RLL(6) MTR(4) code. The encoding method comprises a step of converting a data word into a temporary codeword according to a conversion table for enforcing RLL and MTR constraints, a step of checking violations of the maximum-runlength constraint when concatenating a present and an earlier codeword, and when a violation is detected, a step of selecting one of the present or earlier temporary codeword which has at least four contiguous zeroes adjacent to their boundary, and a step of converting the four zeroes in order to meet the maximum-runlength constraint. Error propagation is reduced by converting one word only upon detection of RLL violation.