Zero coefficient-aware IDCT algorithm for fast video decoding

Ever since many well-known image and video coding standards such as JPEG, MPEG, and H.26x started using DCT as a core process in data compression, the design of the fast inverse discrete cosine transform (IDCT) has been an intensive research topic. Most research has focused on a reduction of the number of operations using the butterfly structure. However, the majority of DCT coefficients is zero after quantization and is therefore redundant for IDCT computation. Therefore, we exploited this DCT coefficients redundancy to propose a zero coefficient-aware IDCT algorithm for fast decoding. The proposed method significantly reduces the number of IDCT operations by adaptively including non-zero coefficients in the calculation and employing a table look-up to eliminate multiplication operations in the IDCT process. The proposed zero coefficient-ware algorithm outperformed other existing fast IDCT algorithms in terms of operational complexity. Moreover, the running time was faster than butterfly based IDCT algorithms implemented in MPEG-4 simple profile decoder by a speedup factor of 1.32 times for the SIF/CIF sequences and up to 2.18 times for the HD sequences.