Two stage coding method

Claim 1

A two stage coding system for encoding digital information arranged in a matrix of k 1 ×q digits in a first direction, and k 2 digits in a second direction orthogonal to the first direction, wherein K 1 , q, and k 2 are integers, K 1 <k 2 ; q=the number of digits per data word, and K 1 , K 2 =the number of data words in said first and second directions respectively, comprising: C 2 encoder means for encoding said digital information with a C 2 code on a Galois Field GF (2 q ), including means for numbering data words in said matrix diagonally from an arbitrary data word a 1 and establishing a 2 to a n2 , wherein n 2 is the length of code C 2 , such that ##EQU8## wherein h 1 to h n .sbsb.2.spsb.-1 satisfy the following h.sub.2i-1 =[K.sub.2 /n.sub.2 ] h.sub.2i =[k.sub.2 /n.sub.2 ]+1 1≦i≦(n.sub.2 -1)/2 means for C 2 encoding said numbered data words, and means for adding the obtained C 2 code to an end of said matrix in said first direction; and C 1 encoder means for encoding said C 2 encoded matrix with a C 1 code having a length of n 1 on a GF (2 q ) for each row of data words in said first direction, and adding the obtained C 1 code to an end of said matrix in said first direction.