Method of converting a stream of databits of a binary information signal into a stream of databits of a constrained binary channel signal, device for encoding, signal comprising a stream of databits of a constrained binary channel signal, record carrier, and device for decoding

A method comprising:

• receiving a sequence of n-bit information words;
• converting the sequence of n-bit information words into a sequence of corresponding channel words, some channel words having m1-bits and other channel words having m2-bits;
• and
• transmitting the sequence of channel words;
• wherein:
• information words are converted into corresponding m1-bit channel words in accordance with a channel code C1;
• information words are converted into corresponding m2-bit channel words in accordance with a channel code C2 that is different than the channel code C1;
• m1, m2 and n are integers for which m2>m1>n;
• the sequence of channel words complies with a runlength constraint and with a second constraint related to the parity of the m2-bit channel words;
• each channel word is selected from a predetermined plurality of channel words of the channel code for the corresponding information word;
• for channel words that immediately follow a previous channel word in the sequence of channel words, the selection depends on an end part of the immediately preceding channel word so that the sequence of channel words complies with the runlength constraint,
• for the conversion into m2-bit channel words, the predetermined plurality of m2-bit channel words includes channel words having opposite polarity, and the selection of the channel word also depends on the second constraint.

An encoder comprising:

• an input that receives a sequence of n-bit information words;
• means for converting the sequence of n-bit information words into a sequence of corresponding channel words, some channel words having m1-bits and other channel words having m2-bits;
• and
• an output that transmits the sequence of channel words;
• wherein:
• information words are converted into the corresponding m1-bit channel words in accordance with a channel code C1;
• information words are converted into corresponding m2-bit channel words in accordance with a channel code C2 that is different than the channel code C1;
• m1, m2 and n are integers for which m2>m1>n;
• m2-bit channel words are chosen from among at least two alternative m2-bit channel words for the same n-bit information word, at least two of the alternative m-bit channel words have opposite parities;
• the sequence of channel words complies with a runlength constraint and with a second constraint related to the parity of the m2-bit channel words;
• each channel word is selected from a predetermined plurality of channel words of the channel code for the corresponding information word;
• for channel words that immediately follow a previous channel word in the sequence of channel words, the selection depends on an end part of the immediately preceding channel word so that the sequence of channel words complies with the runlength constraint;
• for the conversion into m2-bit channel words, the predetermined plurality of m2-bit cbannel words includes channel words having opposite polarity, and the selection of the channel word also depends on the second constraint.

A decoder comprising:

• an input that receives a sequence of channel words, some channel words having m1-bits and other channel words having m2-bits, the sequence of channel words meeting a runlength constraint and another constraint related to the parity of the channel words;
• means for converting the sequence of channel words into a sequence of corresponding n-bit information words;
• and
• an output that transmits the sequence of information words;
• wherein:
• m1-bit channel words are converted into the corresponding information words in accordance with a channel code C1;
• m2-bit channel words are converted into corresponding information words in accordance with a channel code C2 that is different than the channel code C1;
• m1, m2 and n are integers for which m2>m1>n;
• the sequence of channel words complies with a runlength constraint and with a second constraint related to the parity of the m2-bit channel words;
• a plurality of different rnl-bit channel words are converted into a same n-bit information word;
• and
• a plurality of different m2-channel words are converted into the same n-bit information word, the plurality of m2-bit channel words include channel words having opposite polarity.