在H.264/先進視訊編碼壓縮領域中做鏡頭變化的偵測

Abstract

鏡頭變換偵測演算法在自動化的視訊內容分析、索引、以及擷取方面為一基礎的步驟。鏡頭變換的偵測可以應用在很多種視訊技術領域，例如: 視訊編碼解碼的品質與效能以及轉換編碼的的準備等。這篇論文根據intra macroblock預測模式之中的邊的方向性相似度以及intra和inter macroblock個數的比例提出了一個新的H.264/AVC壓縮頻域上鏡頭變換偵測的方法。這篇提出的鏡頭變換偵測演算法包含平緩的鏡頭偵測及切割鏡頭變換的偵測。在平緩鏡頭偵測部份，我們提出了一個褪去鏡頭變換偵測演算法，利用intra macroblock個數的比例以及P_SKIP模式的macroblock個數比例去決定出起始點和終止點。接著，邊的方向性相似度則是利用來判斷目前所偵測到這張宏塊是否包含在褪去鏡頭之中。在切割鏡頭變換的偵測中，我們使用P-MB和B-MB個數的比例去偵測出切割鏡頭變換宏塊的候選者，接者利用我們所提出的邊的方向性相似度去判斷這個候選者是否為一個切割鏡頭變換的宏塊。

Shot change detection algorithm is a fundamental step in automatic video content analysis, indexing, and retrieval. Shot change detection can apply to many kinds of video technology fields, for example, video codec compression quality and performance and transcode preparation…etc. This thesis proposed a new shot change detection method using edge direction similarity based on intra macroblcok prediction mode and the ratio of intra to inter macroblocks in H.264/AVC compression domain. The proposed shot change detection algorithm includes gradual shot change and cut shot change detection. In gradual shot change detection, we proposed a fade shot change detection algorithm, using intra macroblock ratio and P_SKIP macroblock ratio to decide start point and end point. Then edge direction similarity is used to judge if current detected frame is included in the gradual shot or not. In cut shot change detection, we use P-MB and B-MB ratio to detect candidate cut change frame, and then use proposed edge direction similarity to judge the candidate frame is a cut change or not.

The experimental result shows that our proposed algorithm has a high accuracy in terms of recall and precision for a variety of video streams even they are variable bit rates. Our proposed edge direction similarity approach also can enhance shot change detection algorithms and achieve satisfactory performance.