Subband Decomposition for High-Resolution Color in HEVC and AVC 4:2:0 Video Coding Systems

Summary form only given. High-resolution color video (in 4:4:4 format) is becoming increasingly important for screen content and graphics. We have developed a frame packing arrangement (FPA) scheme that enables transmission of 4:4:4 luma-chroma (YUV or YCoCg) content through conventional subsampled chroma (4:2:0) codecs as an approach for low-cost support of 4:4:4 content. We focus on the "band separation" method initially discussed in [1] and evaluate new scenarios with the 4:4:4 and 4:2:0 versions at similar compression levels. We use the HEVC HM12.0 reference software for evaluating the FPA scheme. We vary the luma QP for the main 4:2:0 representation from 10 to 34, keeping the QP for the main frame's chroma and auxiliary frame's luma and chroma (containing three-fourths of the 4:4:4 chroma data) at the same value as the luma QP. We then compare the final 4:4:4 chroma rate-distortion performance of band separation, direct frame packing, and native HM 4:4:4 encoding. We also show preliminary results for lifting-based band separation (with clipping), which eliminates the inherent rounding errors of other band separation filters and provides better rate-distortion performance. Fig. 1 provides an example for a typical case of the new results showing that both the "band separation" and "lifting-based band separation" approaches have much better performance than previously reported, and are significantly better than the earlier-developed "direct" frame packing approach. Although the rate-distortion performance is inferior to that of native HM 4:4:4 coding, the FPA scheme enables the use of existing 4:2:0 decoding hardware, thus allowing for considerable battery power savings in mobile devices. A more complete discussion and evaluation is available in [2].