Method and apparatus for encoding and decoding a binary digital information signal

A method of decoding an encoded binary digital signal comprised of a plurality of n-bit words formed by converting each of a plurality of first n-bit words having a digital sum variation into a respective second n-bit word having a digital sum variation such that, with respect to predetermined groups of correlative first n-bit words in which successive first n-bit words have values close to each other, said second n-bit words corresponding to said first n-bit words in each respectively group have the same digital sum variation, and inverting every m.sup.th one of said second n-bit words, where m=2, 3 . . ., comprising the steps of:

• inverting every m.sup.th one of said n-bit words of said encoded binary digital signal to form a non-inverted encoded binary digital signal comprised of said second n-bit words;
• and
• converting each of said second n-bit words back to the respective one of said first n-bit words to form an original binary digital signal.

Apparatus for encoding a binary digital signal provided at a source bit rate and formed of a plurality of first n-bit words having a digital sum variation to produce an encoded binary digital signal having a reduced digital sum variation at said source bit rate, comprising:

• means for converting each first n-bit word into a second n-bit word having a digital sum variation such that, with respect to predetermined groups of correlative first n-bit words in which successive words have values close to each other, said means for converting including means for arranging said second n-bit words in groups having the same digital sum variation;
• and
• means for inverting every m.sup.th one of said n-bit words, where m=2, 3 . . .

Apparatus for decoding an encoded binary digital signal comprised of a plurality of n-bit words formed by converting each of plurality of first n-bit words having a digital sum variation into a respective second n-bit word having a digital sum variation such that, with respect to predetermined groups of correlative first n-bit words in which successive first n-bit words have values close to each other, said second n-bit words corresponding to said first n-bit words in each respective group have the same digital sum variation, and inverting every m.sup.th one of said second n-bit words, where m=2, 3 . . . , comprising:

• means for inverting every m.sup.th one of said n-bit words of said encoded binary digital signal to form a non-inverted encoded binary digital signal comprised of said second n-bit words;
• and
• means for converting each of said second n-bit words back to the respective one of said first n-bit words to form an original binary digital signal.