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 the RGB color space maintains high color fidelity, having the drawback of a substantial bitrate 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 points of view, from theoretical background to practical implementation. The proposed CCP scheme has been evaluated in standardization communities and adopted into H.265/High Efficiency Video Coding (HEVC) Range Extensions. The experimental results show significant coding performance improvements for both 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% bitrate reduction in the case of intra coding and 11% and 4% in the 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.

Palette mode is a new coding tool included in the HEVC screen content coding extension (SCC) to improve the coding efficiency for screen contents such as computer generated video with substantial amount of text and graphics. It is observed that a local area in screen content typically has a few colors separated by sharp edges. To exploit such characteristics, palette mode represents samples in a block with indexes pointing to the color entries in a palette table. This paper provides a detailed overview of the palette mode in HEVC SCC in terms of palette generation, coding of the palette, and coding of the palette indexes for the samples in the palette block. Several improvements to palette mode coding, which have been proposed but not included in HEVC SCC, are also described. Simulation results are presented to quantify the bitrate savings provided by the palette mode for equal distortions.

Based on the dynamic reactive power supporting ability of DFIG,the scheme proposed in this paper can be used to coordinate the reactive power outputs of the grid side converter (GSC)and the generator to maintain the safe operation of the DC capacitor. The safety value of the interface voltage of the DFIG is defined according to the high voltage ride-through requirements of the DC capacitor. Based on the safety voltage, the judgment basis is given to judge whether the DFIG can ride through the high voltage fault during the grid voltage swell,and the strategies of the reactive outputs of the grid side converter (GSC)during the high voltage ride-through are also given. The simulation results verify correctness of the proposed scheme.