The encoder chip of the present invention uses LDPC codes to encode input message data at a transmitting end, thereby generating a series of codewords. The encoder chip implements two low-density parity-check (LDPC) codes. The first LDPC code is a (4088,3360) code (4K) which is shortened from a (4095,3367) cyclic code. The second LDPC code is a quasi-cyclic (8158,7136) code (8K). The message data and the generated codewords are transmitted to a receiving end where the received codewords are decoded and checked for errors. To generate the codewords, the encoder applies a generator matrix G to the input message data. The G matrix is generated by first defining an H matrix. An H matrix is initially defined as 16.times.2 array of right-circulant sub-matrices. The G matrix is formed by manipulating the H matrix according to a 4-step algorithm. A randomizer and a synchronization marker are also included within the encoder.