# US 4,531,153 A · Method and apparatus for encoding and decoding a binary digital information signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,531,153 A - Document ID: US4531153A - Status: Granted - Kind: A - Application number: 06/437,700 - Filed: 1982-10-29 - Granted: 1985-07-23 - Earliest claimed: 1982-10-29 - Assignees: Sony Corporation - Inventors: Kenji Watanabe - Web page: https://patentgrep.com/patent/US4531153A ## CPC - H04L 25/4906: {using binary codes} - G11B 20/1426: {conversion to or from block codes or representations thereof} - H04N 5/926: by pulse code modulation (H04N5/919 takes precedence) - G11B 2020/1434: {8 to 9 modulation} - G11B 2020/1438: {8 to 10 modulation} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A system of encoding an original binary digital video signal comprised of a plurality of first 8-bit words having an absolute value and a digital sum variation, to produce an encoded binary digital video signal, converts each first 8-bit word into a second 8-bit word also having an absolute value and a digital sum variation such that, with respect to predetermined groups of correlative first 8-bit words, that is, first 8-bit words having absolute values which are close to each other, second 8-bit words corresponding to the first 8-bit words in each respective group have the same digital sum variation; and then inverts every alternate m second 8-bit words, where m=1, 2, 3 . . . , to form the encoded binary digital video signal with substantially reduced DC content while maintaining the same recording bit rate. ## Claims ### Claim 1 A method for use with a binary digital signal provided at a source bit rate and formed of a plurality of first n-bit words that correlate in value such that successive words have values close to each other and which have a digital sum variation to produce an encoded binary digital signal having a reduced digital sum variation without increasing the source bit rate, comprising the steps of: arranging second n-bit words into groups classified by the digital sum variation values thereof, so that the second n-bit words in each group have substantially the same digital sum variation values; substituting said groups of second n-bit words for groups of corresponding first n-bit words having the same number of words and being arranged in sequential order; and inverting every m.sup.th one of said second n-bit words, where m=2, 3, . . . ### Claim 2 (depends on 1) A method according to claim 1; in which n=8. ### Claim 3 (depends on 1) A method according to claim 1; in which each of said predetermined groups includes a plurality of first n-bit words having successively increasing integer values. ### Claim 4 (depends on 1) A method according to claim 1; in which at least one first n-bit word not included in any of said predetermined groups is converted into at least one corresponding second n-bit word which is identical to the respective at least one first n-bit word. ### Claim 5 (depends on 1) A method according to claim 1, further comprising the step of arranging said first n-bit words in said groups in succesively decreasing numerical order. ### Claim 6 (depends on 1) A method according to claim 1; in which said binary digital signal is a digitized video signal comprised of a plurality of horizontal lines, each horizontal line being formed of g first n-bit words. ### Claim 7 (depends on 6) A method according to claim 6, including the further step of inverting ever r.sup.th one of said plurality of horizontal lines, where r=2, 3, . . . . ### Claim 8 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. ### Claim 9 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 . . . ### Claim 10 (depends on 9) Apparatus according to claim 9; in which said binary digital signal is a digitized video signal comprised of a plurality of horizontal lines, each horizontal line being formed of q first n-bit words. ### Claim 11 (depends on 9) Apparatus according to claim 9; in which n=8. ### Claim 12 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.