隨著科技的發展，影像/視訊內容的分享越來越普及，許多人喜歡將生活周遭發生的事物透過行動裝置，例如：手機、PDA、…等，立即分享給親朋好友。但是受限於行動裝置螢幕大小的限制，我們必須對於這些影像/視訊進行畫面濃縮處理才能在這些行動裝置上進行播放。但無可避免的這個過程會造成資訊上的損失。近年來已經有不少研究課題討論如何實現基於內容為主的影像/視訊畫面濃縮，目的是希望畫面經過濃縮之後能盡量維持畫面中人眼感興趣的區域，並且縮小或裁切掉人眼較不感興趣的區域，使得濃縮後的影像/視訊能呈現原始影像/視訊所要分享的訊息。然而，對於濃縮後的視訊如何確保畫面之間在空間軸上以及時軸上的一致性將會是影響視訊品質的關鍵。目前現存的方法對於同時包含有背景鏡頭移動與物體移動的影片很難在畫面濃縮後保持在時軸上的一致性。因此這裡我們提出了一個新的視訊濃縮方法，利用全景接圖導引的方式去決定每一個相對應區域的縮放比例，以確保畫面之間在時軸上的一致性。我們提出的方法先將影片中屬於同一個場景的每一張畫面接合產生一張全景圖，並根據全景圖產生一張全域縮放圖，接著每一張畫面參考全域縮放圖上的資訊與提出的空間軸上限制做最佳化處理，最後得到每一張畫面個別的局部縮放圖和濃縮後的畫面。實驗的結果顯示我們提出的視訊濃縮方法可以有效維持濃縮後的視訊畫面在時軸上的一致性，甚至對於包含有背景鏡頭移動與物體移動的影片也能有不錯的效果。

Video retargeting from a full-resolution video to a lower-resolution display will inevitably cause information loss. Content-aware video retargeting techniques have been studied to avoid critical visual information loss while retargeting a video. Maintaining the spatio-temporal coherence of a retargeted video is very critical on visual quality. Camera motions and object motions, however, usually make it difficult to maintain temporal coherence with existing video retargeting schemes. In this thesis, we propose the use of a panoramic mosaic to guide the scaling of corresponding regions of video frames in a video shot to ensure good temporal coherence. In the proposed method, after aligning video frames in a shot to a panoramic mosaic constructed for the shot, a global scaling map for these frames is derived from the panoramic mosaic. Subsequently, the local scaling maps of individual frames are derived from the global map and is further refined according to spatial coherence constraints. Our experimental results show that the proposed method can effectively maintain temporal coherence so as to achieve good visual quality even a video contains camera motions and object motions.

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