Exploiting Non-Local Correlation via Signal-Dependent Transform (SDT)

Over the past few decades, many studies on image and video compression have found various approaches to the exploitation of spatial and temporal local correlations. However, we believe it is imperative to find more efficient methods to progress the development of image and video compression. In this paper, we first study spatial non-local correlation, deducing that there exist strong correlations in non-local regions. However, it is rather difficult to make use of these non-local correlations while simultaneously minimizing overhead. To solve this problem, we propose the signal-dependent transform (SDT), which is derived from decoded non-local blocks that are selected by matching neighboring pixels. Since the encoder and decoder can use the same methods to derive the proposed transform, we can successfully eliminate overhead. Finally, we have implemented the proposed transform into the Key Technology Area (KTA) software to exploit both spatial and temporal non-local correlations. The experimental results show that the coding gain over KTA can be as high as 1.4 dB in intra-frame coding, and up to 1.0 dB in inter-frame coding. We believe we have effectively created an alternate method to improve image and video compression.