在監視系統被大量建置的趨勢下，表示有愈來愈多的影像需要被儲存，該如何節省儲存的空間便成為很重要的議題。然而，所有的解決方案卻都著墨在影像壓縮技術上！此外，瀏覽儲存好的影像也不輕鬆，必須浪費許多時間從每天二十四小時不斷錄製的影像中，搜尋出特定的人事物。目前雖有影像摘要技術來節省瀏覽時間，但卻得另外花費空間來儲存這些濃縮的影像。總之沒有同使可以解決以上兩大問題的方式。 所以，本論文基於Video Synopsis的概念，提出了一套影像處理流程；首先使用對稱性遮罩小波轉換（Symmetric Mask-based Discrete Wavelet Transform）來進行影像解析度的降階（Dyadic Down Sampling），並利用其低通濾波器的特性，濾除外界環境的雜訊與偽動作（Fake Motion）；再去除時間軸的冗餘資訊，把未有事件發生的畫面刪除；之後利用自行設計的演算法，擷取出前景物件，最後計算畫面上的空間資訊，將連續事件整合於一張畫面上。如此一來，因為整合了連續的事件，便達成了精簡畫面張數的效果，且其中並未對原始像素值做任何變更，藉此完成了影像大量無損（Lossless）壓縮的目的，同時也縮減了影像的播放時間。 分析實驗結果，本論文提出的儲存解決方案，可適應室內與室外環境的自然變化，且只需花費原始未壓縮影像約15%以下的儲存空間；在VGA的解析度下亦可達到23 FPS的即時（Real-time）處理效能，故播放時間也就只需要15%左右，可快速瀏覽完畢一段影像。 此法不同於以往的影像壓縮，產生的簡短影像還可以再使用任何壓縮法來更加地減少儲存空間，是相當有效的低影像儲存容量技術。 Since there are more than one million surveillance cameras in public space of a city, we have faced the age of surveillance system. The most painful task is retrieving those volumes of video and trying to find some available capacity to store them in. The conventional way to shrink the video is compression, however this method causes some disadvantages, such as saving miserable space with lossless compression, and poor evidence with lossy compression. The conventional way to retrieve video is abstraction and index, but it is incompatible with video archiving because it needs more capacity. This thesis presented a solution that can have it in both ways. The approach based on Video Synopsis uses the LL sub-band which is obtained from Symmetric Mask-based Discrete Wavelet Transform to down-sample the resolution of frames, so that the computing coast of the following step in this proposed flow could be reduced easily, and the high frequency noise could be decreased in the meanwhile. Then some algorithms are proposed to extract foreground objects. The key part is that the thesis proposed an algorithm to calculate the spatial information for showing objects simultaneously which originally occurred at different times, just like the stroboscopic effect. According to the experimental result, this solution has some merits: good efficiency to handle real-time video archiving with 23 FPS in VGA resolution, lossless recording, only need low storage capacity with about below 15% space of original video, the duration of the generated video is about 15% run-time of original one, and suitable for outdoor environment.
