為了減少成本，絕大多數的監視器與網路攝影機皆採用單一感光元件並搭載RGB色彩濾波陣列來捕捉影像。由於在捕捉的影像中，任一像素點上只會儲存RGB其中一種顏色的資訊，因此這類的影像通常被稱之為馬賽克影像。傳統上這些設備必須先經過解馬賽克與RGB至YUV色彩空間轉換後，再進行UV彩度抽樣與影像壓縮，來降低影像所需之儲存空間或傳輸頻寬。然而在傳統壓縮流程中，UV彩度抽樣總是在固定的影像位置進行彩度抽樣，完全沒有考慮到抽樣的結果對於重建馬賽克影像中RGB像素的影響性。在本篇論文中，我們提出了一種在HEVC壓縮標準下適用於任意色彩濾波陣列馬賽克視訊之調整式4:2:2彩度抽樣策略。透過觀察傳統彩度抽樣策略的缺陷與YUV至RGB色彩空間轉換的特性，在所提出的調整式4:2:2彩度抽樣策略中，我們納入UV彩度對於重建馬賽克影像中RGB像素的不同影響權重， 藉此有效動態地調整彩度抽樣位置。實驗結果顯示，相較於傳統的彩度抽樣策略，我們所提出之彩度抽樣策略確實能在不同bitrate區段上有效增進重建後馬賽克與解碼賽克視訊品質。

To reduce the cost, most of surveillance cameras
and web cameras are equipped with a single sensor covered by
a red-green-blue (RGB) color filter array (CFA) for capturing
only one RGB color component per pixel and hence produce
so-called mosaic images. Conventionally, such cameras perform
demosaicking, the transform from RGB domain to YUV domain,
the chroma subsampling with 4:2:2 format, and the video coding
to compress the captured mosaic images for storage saving and
transmission over the Internet. However, in the conventional compression
scheme, the commonly used 4:2:2 chroma subsampling
strategies always sample U and V components from the fixed
positions without considering the significance of the sampled U
and V components for reconstructing R, G and B pixels, which
results in the quality degradation of the reconstructed videos. In
this thesis, to remedy this weakness, we propose an adjusted 4:2:2
chroma subsampling strategy for compressing mosaic videos
with arbitrary RGB-CFA structures in HEVC. The novelty of
our work lies on that the positions of the sampled U and V
components are dynamically adjusted according to the ordered
significance of the U component for reconstructing B and G pixels
as well as the V component for reconstructing R and G pixels.
Experimental results demonstrate that the proposed adjusted
4:2:2 chroma subsampling strategy outperforms, in terms of the
quality of the reconstructed mosaic videos and the reconstructed
full-color videos, the commonly used ones in the cases of middle
and high bitrate and is competitive with the commonly used ones
in the case of low bitrate.

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