Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/6179
標題: 一種適用於低位元速率視訊壓縮之預估性區塊匹配移動估算快速演算法
A Fast Predictive Block-Matching Motion Estimation Algorithm for Low Bit-Rate Coding
作者: 沈志賢
關鍵字: motion vector;移動向量;predictive motion estimation;block-matching algorithm;H.263 three-block median predictor;預估性移動估算;區塊匹配演算法;H.263 三區塊中位數預估器
出版社: 電機工程學系
摘要: 
對於低位元速率視訊編碼,預估性區塊匹配移動估算演算法常被用來取代對數步階搜尋演算法,這是因為移動向量之間的關係可用來大幅地縮短尋找移動向量的時間。然而,若移動向量一開始的預估不夠準確,這些演算法仍然需要龐大的計算量。因此,搜尋移動向量的時間會隨著不同畫面而有劇烈的變化。本篇論文中,我們詳細地探討移動向量之間的關係。從實驗結果發現,移動向量的x分量和其垂直相鄰的移動向量關係較大,而y分量和其水平相鄰的移動向量比較相關。根據這個觀察結果,我們設計一個改良的三區塊中位數預估器來增加預估移動向量的準確度。藉由這個預估器,我們提出一個預估性區塊匹配移動估算的快速演算法,稱為向量找尋演算法。這個演算法只朝著最可能的方向搜尋,而不是每個方向都找。模擬結果顯示,我們的演算法不僅比其他的快速演算法都要快很多,而且其效能﹝均方誤差﹞更好或是差不多。

For low bit-rate video coding, predictive block-matching motion estimation algorithms have been used to replace the logarithmic step search algorithms because the motion vector searching time can be greatly reduced by utilizing the correlation existing in motion vectors. However, these algorithms still suffer from their large computations if the initial prediction is not accurate enough. As a result, the motion vector searching time can vary acutely from frame to frame. In this article, we investigate the correlation among motion vectors (MV). Our study shows that the x component of MV is more related to its vertical neighbor MVs while the y component of MV is more depedent on its horizontal neighbor MVs. Based on the observation, we design a modified three-block median predictor to improve the motion vector predicting accuracy. By employing the predictor, a fast predictive block-matching motion estimation algorithm, the vector search algorithm (VSA), is proposed. Instead of checking all locations in the search area, the VSA only searches locations in the most probable direction. Simulation results indicate that our algorithm is much faster than other fast search algorithms as well as maintaining similar or better performance in terms of mean-square error measurement.
URI: http://hdl.handle.net/11455/6179
Appears in Collections:電機工程學系所

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