藉由主角移動軌跡之分析來測定隱晦不明顯之影片分鏡時間點

Obscure Video-Shot Boundary Determination via Protagonist Trajectory Analysis

陳彥呈(Albert Y. C. Chen)

指導教授 ： 李忠謀

國立臺灣師範大學/教育學院/資訊教育學系/碩士(2006年)

摘要

過去對於影片檢索方面的研究，多半專注於「有明顯分鏡」的影片，像是電影與新聞錄影。此類影片在「分鏡」時，整個畫面的像素通常會有顯著的改變，而系統便可藉此判斷出分鏡的時間，進而對影片進行切割或是編輯索引。
本研究著重於「無顯著分鏡」影片的研究。此類影片雖為一鏡到底，但影片中的內容與主角，通常會隨著時間而有所變動。傳統的演算法，無法偵測出此「不明顯」的分鏡時機，進而必須藉由更高階的資訊來判斷何時分鏡。
本研究所提出的演算法，可概分為「移動物體的擷取」與「主角變換的偵測」兩大模組。移動物體的擷取，可依照相機本身的位移與否，分為兩大類型。本研究的相機為固定式，採取「改良式單一高氏分佈」來建立畫面背景，再藉由背景消去法來獲取屬於前景的移動中物體。取得移動物體後，藉由追蹤「最大前景物體」軸心於橫軸方向的位移量，與主角平均高度，來判斷主角何時換人。當偵測到主角換人時，影片內容應該已有劇烈的改變，因而我們將此時間點稱為「隱諱不明」的分鏡時間點。我們所提的這個演算法，能夠讓此類「無顯著分鏡」影片的切割與索引編輯過程自動化，進而使數位影片的典藏與存取更加的容易。

關鍵字

影片檢索 ； 影片分割 ； 分鏡 ； 移動物體擷取 ； 背景消去

並列摘要

Previous research related to Video Indexing had primarily centered on videos with obvious video-shot boundaries, such as movies and recordings of news broadcast. When we encounter a video-shot boundary in the types of film mentioned above, the pixels within the whole scene would alter at a noticeable level, thus allowing the computer to automatically segment and index the video according to the video-shot boundaries.
Our research focuses on detecting possible cut points for videos without obvious video-shot boundaries. Although these videos were often recorded continuously without film cuts, the content and people within the film could change rapidly during the recording period. Traditional video-shot boundary detection algorithms cannot successfully detect this kind of content change, which we call as obscure video-shot boundaries, thus we would have to depend on higher level understandings of the film to determine appropriate time points to serve as film cuts.
Our proposed algorithm can be roughly classified into two major modules: the moving object segmentation module, and the protagonist-change detection module. Moving object segmentation algorithms can be classified into two categories based on whether the camera moves or not. Our method is applicable only to videos recorded by a static camera, which uses an improved univariate Gaussian background module to perform background subtraction and to extract the foreground moving objects. The largest moving object would be detected and tracked, while its average height and horizontal moving distance would be exploited to determine protagonist change. Whenever a protagonist change occurs, we can conclude that the video content had changed rapidly and meaningfully, thus the time point can be used to serve as a candidate segmentation point. Our proposed algorithm can automate the segmentation and indexing process of those videos without obvious video-shot boundaries, thus greatly reduce the time and effort needed in digital archiving.

並列關鍵字

Video Indexing ； Video Segmentation ； Video-Shot Boundary ； Moving Object Segmentation ； Background Subtraction

參考文獻

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