In a channel encoder comprising a dk-encoder stage and a precoding stage, obeyance of a repeated minimum transition runlength constraint is achieved because, between the dk-encoder and the precoder, data are passed through an RMTR encoder which replaces occurrences of a forbidden pattern by a current replacement pattern having the same length as the forbidden pattern. By appropriately selecting current replacement patterns from a predefined set of two different replacement patterns, DC-control can be achieved for the encoder output. The corresponding decoder is described, which also employs pattern replacement.These results are provided by a method of channel encoding binary data, wherein the data is contained in a n input sequence of data tuples. An input sequence of constrained tuples is generated that obeys the relationships heretorfore set forth. A post encoding step is applied with NRZI modulation to be used in a channel as described.