Image and Video Processing Lab, The Chinese University of Hong Kong


1. Project Description


The mode-dependent directional transform (MDDT) employed Karhunen–Loève Transform (KLT) for compressing directional residue signal of intra prediction along its direction. The transform bases were derived from the singular value decomposition (SVD) of residue signals coming from all kinds of video sequences, which were expected to be efficient for most of video sequences. However, the advantage of KLT comes from the concept of a "signal content dependent transform". MDDT and its variants failed to exploit such a concept, so they did not fully exploit the efficiency of KLT. In our work, we employ a set of KLT bases to cater for each category of video sequences. All video sequences of the same category are assumed to have an identical feature of video content. The classification of video content could utilize any criteria capable of identifying the difference in video content. We use the histogram of the intra prediction residues to classify the video sequences on the training set into several classes. Thus, there are multiple sets of KLT bases provided for the encoder in the proposed algorithm. During the encoding process, one set of KLT bases is selected for a frame according to the feature matching process.

2. Flowchart



3. Experimental Results





4. Group members


-   PhD student: Miaohui Wang (

-   PostDoc: Long Xu (

-   Supervisor: King Ngi Ngan (


5. References


[1] Y. Ye and M. Karczewicz, "Improved H.264 intra coding based on bidirectional intra prediction, directional transform, and adaptive coefficient scanning," in Proc. IEEE Int. Conf. Image Process., Oct. 2008, pp. 2116C2119.

[2] Y. Ye and M. Karczewicz, "Improved Intra Coding," ITU-T Q.6/SG16, 33rd Meeting: Shenzhen, China, 20 October, 2007. 

[3] X. Zhao, L. Zhang, S. W. Ma, and W. Gao, "Video Coding with Rate-Distortion Optimized Transform," IEEE Trans. Circuit & Syst. On Video Technol., 2011. 

[4] J. Dong and King N. Ngan, "Two-Layer Directional Transform for High Performance Video Coding," IEEE Trans. Circuit & Syst. On Video Technol.619-625, 2012 

[5] B. Zeng and J. Fu, "Directional discrete cosine transforms: A new framework for image coding," IEEE Trans. Circuits Syst. Video Technol., vol. 18, no. 3, pp. 305C313, Mar. 2008. 

[6] Fatih Kamisli and Jae S. Lim, "Directional discrete cosine transforms: A new framework for image coding," IEEE Trans. on Image Processing, VOL. 20, NO. 4,pp 1036-1046, APRIL 2011

[7] Chuohao Yeo, Yih Han Tan, Zhengguo Li and Susanto Rahardja, "Mode-dependent transforms for coding directional intra prediction residuals," IEEE Trans. Circuits Syst. Video Technol,VOL. 22, NO. 4, pp 621 - 624 APRIL 2012. 

[8] C.-L. Chang, M. Makar, S. Tsai, and B. Girod, "Direction-adaptive partitioned block transform for color image coding," IEEE Trans. Image Process., vol. 19, no. 7, pp. 1740C1755, Jul. 2010.