Method and apparatus are provided for encoding and decoding rate-(s(K+1))/(s(K+1)+1) TCMTR(j,k,t,a) codes, where s is the ECC symbol size in bits and K is the number of unencoded symbols that are interleaved with an (s+1)-bit encoded block at the output of a rate-s/(s+1) encoder that encodes the r-th 5-bit symbol. K=m/s-1 where m=s(K+1) is the total number of bits to be encoded. Error propagation is reduced, thus allowing the ECC code to correct errors efficiently. Header error-rate is also reduced by eliminating occurrence of likely error events at the detector output. Although initially an RLL code may be designed for an ECC symbol size of s bits, the RLL encoding of the present invention may be used in conjunction with ECC schemes that utilize symbol sizes other than s bits.