Frequency Domain Intra Pattern Copy for JPEG XS Screen Content Coding

JPEG XS is a wavelet-based lightweight image coding standard that features low-complexity and low-latency. As currently there are no efficient intra-compensation prediction techniques conforming to these features, we propose a frequency domain intra-copy prediction framework named Intra Pattern Copy (IPC), to improve its coding efficiency on screen content. In IPC, prediction methods that leverage the diverse decomposed patterns of two-dimensional wavelets, including the directional and frequency characteristics, are proposed to achieve efficient predictions under low-complexity and low-latency constraints. Specifically, we perform in-band compensation predictions in a multi-band synchronized approach, with coefficients of similar pattern distributions predicted simultaneously. A coefficient grouping scheme is derived from the band characteristics to facilitate this compensation process. Based on the grouping scheme, a multi-band synchronized side information coding method is also proposed to code the pattern offset vector of coefficients. Moreover, pattern search schemes incorporating strict limitations on the search range and prediction block size are further developed. Simulation results on JPEG XS demonstrate that an average improvement of 0.75 dB and 1.99 dB in BD-PSNR can be achieved on screen content for two different wavelet decomposition configurations, respectively, with a moderate increase in complexity.