Cross-Component Prediction in HEVC

Video coding in the YCbCr color space has been widely used, since it is efficient for compression, but it can result in color distortion due to conversion error. Meanwhile, coding in RGB color space maintains high color fidelity, having the drawback of a substantial bit-rate increase with respect to YCbCr coding. Cross-component prediction (CCP) efficiently compresses video content by decorrelating color components while keeping high color fidelity. In this scheme, the chroma residual signal is predicted from the luma residual signal inside the coding loop. This paper gives a description of the CCP scheme from several point-of-view, from theoretical background to practical implementation. The proposed CCP scheme has been evaluated in standardization communities and adopted into H.265/HEVC Range Extensions. Experimental results show significant coding performance improvements both for natural and screen content video, while the quality of all color components is maintained. The average coding gains for natural video are 17% and 5% bit-rate reduction in case of intra coding, and 11% and 4% in case of inter coding for RGB and YCbCr coding, respectively, while the average increment of encoding and decoding times in the HEVC reference software implementation are 10% and 4%, respectively.