Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/7456
標題: 一種以區塊為基礎的預測性運動向量估測演算法
A Modified Predictive Algorithm for Block-based Motion Estimation
作者: 許進裕
Sheu, Jinn-Yuh
關鍵字: New cross search algorithm;新十字搜尋演算法;motion estimation;predictive search algorithm;halfway-stop mechanism;multiple starting points;運動估測;預測性搜尋演算法;中途停止機制;多重搜尋起點
出版社: 電機工程學系
摘要: 
我們提出了一個運用於連續影像壓縮中新的預測性運動向量搜尋演算法,並且將之取名為新十字搜尋演算法,此種演算法可以在維持影像品質的前提下有效的提升運動向量的尋找速度。為了降低搜尋過程中陷入區域極小值內的機率,我們採取了多重搜尋起點的策略並且搭配對區塊匹配中像素的次取樣機制來維持搜尋的速度。而在計算區塊誤差時,我們允許在誤差值已高於最小誤差時,中途停止此候選運動向量的區塊誤差計算,以避免計算資源的浪費。此外,當目前所計算出的最小區塊誤差低於所設定之門檻值時,我們也會提早結束此運動向量的尋找,並且以此最小誤差區塊的位移作為該區愧的運動向量。模擬結果顯示使用本演算法相對於預測性找尋演算法最多可減少百分之八十八的計算量,而平均也可減少百分之七十八的計算量,若與向量找尋演算法相比,則本演算法有效的減少了許多不必要的運算並且提升了影像品質。透過以上的模擬結果,我們知道新十字搜尋演算法的確能在維持影像品質的前提下,有效的加快運動向量的搜尋速度,因此,本演算法可以提供作為即時影像壓縮編碼器中運動向量搜尋演算法的新選擇。

A new cross search (NCS) algorithm, which can efficiently reduce the computational load, is proposed. To reduce the probability of being trapped into local minimum in motion vector search, the NCS algorithm initiates its search with multiple starting points meanwhile utilize the pixel sub-sampling method to maintain a low computational load. In order to early reject non-possible candidate motion vector, the NCS algorithm adopts a halfway-stop mechanism into the computation process of block distortion measurement. Furthermore, we introduce a threshold value to early stop if the current minimum block error is less than the threshold value. Simulation results show that by using the NCS algorithm we can reduce up to 88% computational load and 78% on average compared to the PSA meanwhile maintaining similar PSNR and MSE performance. When compares with VSA, the NCS can reduce redundant computation and improve the performance. The proposed NCS algorithm is suitable for real-time video encoding as it can speed up the encoder without sacrificing PSNR performance.
URI: http://hdl.handle.net/11455/7456
Appears in Collections:電機工程學系所

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