Low-Complexity Order-64 Integer Cosine Transform Design and its Application in HEVC

• Published in: IEEE transactions on circuits and systems for video technology Vol. 28; no. 9; pp. 2407 - 2412
• Main Authors: Chen, Zhe, Han, Qinglong, Cham, Wai-Kuen
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-09-2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Coding; Complexity; Complexity theory; DCT; Discrete cosine transforms; Encoding; HEVC; ICT; Kernel; Model testing; Transform coding; Video coding; Video compression
• ISSN: 1051-8215; 1558-2205
• DOI: 10.1109/TCSVT.2018.2822319

In high efficiency video coding (HEVC) standard, residuals are partitioned into variable-size transform units, and integer cosine transforms (ICTs) of order-4, 8, 16, and 32 are adopted to optimize the coding performance. Order-64 ICT is not used due to its high complexity and limited gain in general coding applications. This paper proposes a set of low-complexity ICTs (LCICTs), from order-8 to order-64, which have fully factorizable structures. LCICTs achieve similar coding performance as the state-of-art methods on HEVC Test Model 13 while requiring lower complexity, e.g., 71% fewer multiplications than the partially factorizable ICTs in the order-64 case. Moreover, we find that order-64 ICTs achieve around 1% average bitrate reduction at high quantization parameters.