Combi-codes for DC-free runlength-limited coding
W. Coene · IEEE Transactions on Consumer Electronics · 2000
We present a new coding scheme for DC-free runlength-limited (RLL) codes. This scheme is based on the combination of two codes, a main code and a substitution code, both operating on symbols of a fixed length n. The substitution code has a special structure, i.e., for each n-bit symbol, there are two possible channel words, which have opposite parity and the same next-state in the underlying finite-state machine (FSM). The advantages of this systematic structure of the code are: guaranteed DC-control, ECC-symbol oriented coding, and low-complexity look-ahead DC-control encoding. A design for an efficient combi-code for both for EFM-like RLL constraints (d=2, k=10) and for (d=1, k=7) RLL constraints, is outlined.