  Bliss schemes of a run length limited (RLL) codec in combination with an LDPC
codec, generate LDPC parity bits over a systematic sequence of RLL channel bits
that are inherently redundant as they satisfy e.g. a $d=1$ minimum run length
constraint. That is the subsequences consisting of runs of length $d=1$, viz.
$...010...$ and $...101...$, cannot occur. We propose to use this redundancy
during LDPC decoding in a Bliss scheme by introducing additional $d$-constraint
nodes in the factor graph used by the LDPC decoder. The messages sent from
these new nodes to the variable or codeword bit nodes exert a ``force'' on the
resulting soft-bit vector coming out of the LDPC decoding that give it a
tendency to comply with the $d$-constraints. This way, we can significantly
reduce the probability of decoding error.
