Fixed-point zero coefficient-aware fast IQ-IDCT algorithm

In this paper, we propose a fixed-point zero coefficient-aware fast IQ-IDCT algorithm to reduce the computational complexity of discrete cosine transform and cope with mismatch of decoded data in between encoder and decoder. The major theme of this paper is based on zero coefficient-aware design, which reduces the computational complexity of inverse DCT algorithms by avoiding unnecessary computations caused by zero DCT coefficients. We extended the zero coefficient-aware design to the inverse quantization stage to farther reduce the computational complexity of inverse quantization and inverse DCT by avoiding computations with zero quantized DCT coefficients. In order to maximize the computational complexity reduction as well as to preserve precision accuracy of the ideal IQ-IDCT process, the proposed method employs the fixed-point approximation scheme on all computational procedures of the IQ-IDCT based on table-lookup operations with accurate dyadic terms. As a result, we have achieved a speedup by factor of 3.1 on average compared to the fixed-point 8×8 inverse discrete cosine transform standard.