在服務端對輸入的RGB全彩影像I^{RGB}進行編碼前，對轉換後的彩度影像執行彩度抽樣是必要的步驟。在客戶端收到解壓縮後的抽樣彩度影像及亮度影像，進行彩度重建也是重建RGB全彩影像的必要步驟。在本篇論文中，考慮了七種常用的彩度抽樣方法，用Cs表示，四種彩度重建方法，用Cu表示，我們首先分析了CsxCu組合中發生的座標位移問題。接著我們解釋為什麼座標位移問題會降低重建影像的品質。為了補救這個座標位移問題，我們提出了一種基於CD vector(CDV)的品質增強方法來提高重建影像的品質。據我們所知，這是該研究方向的第一項工作。基於IMAX、柯達、螢幕內容影像和影片的資料集，綜合實驗的全面結果顯示出在新發布的通用影片壓縮平台VTM-12.0上，我們的基於CDV的品質增強方法於擴充的壓縮系統平台上可以在CsxCu中實現17種組合實質上的品質改良。

Prior to encoding an input RGB full-color image I^{RGB}, at the server side, performing chroma subsampling on the converted chroma image is a necessary step. After receiving the decompressed subsampled chroma image and luma image, at the client side, performing chroma upsampling is also a necessary step for reconstructing the RGB full-color image. In this paper, considering seven commonly used chroma subsampling methods, denoted by Cs, and four chroma upsampling methods, denoted by Cu, we first analyze the coordinate displacement (CD) problem happened to the combinations in CsxCu. Next, we explain why the CD problem degrades the quality of the reconstructed images. To remedy this CD problem, a CD vector (CDV) based quality enhancement method is proposed to improve the quality of the reconstructed images. To the best of our knowledge, this is the first work in this research direction. Based on the IMAX, Kodak, SCI (screen content images), and Video datasets, the comprehensive experimental results demonstrated that on the newly released versatile video coding (VVC) platform VTM-12.0, the proposed CDV based quality enhancement method in our augmented coding system can achieve substantial quality improvement for 17 combinations in CsxCu.

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