整合式解交錯演算法之設計

Abstract

在最近幾年，數位電視已經開始播放和循序掃描的輸出顯示裝置已普及一般家庭，因此將交錯掃描轉換成循序掃描的解交錯(De-interlacing)演算法就變得相當重要，雖然移動可適性解交錯(Motion Adaptive De-interlacing)的演算法已經廣泛應用在現今許多的商品上，但在某些移動區域的畫質仍有需要再提昇。 本篇論文提出的整合式解交錯(Integrated De-interlacing)的演算法，可以有效提昇移動區域的畫面，但是當移動估計不正確時，反而會使移動補償後的畫面變得很差，為了改善這種情況，因此結合移動可適性解交錯的優點，並將空間圖場內插(Spatial Interpolation)的方式改成ELA(Edge Line Average)來設計，經過電腦模擬的結果發現，不僅在視覺上提高畫面的解析度，在某些影像峰值訊號雜訊比(Peak Signal Noise Ratio , PSNR)也比線平均解交 錯(Line Average De-interlacing)多出好幾分貝的畫質增益。 此外，在整合式解交錯演算法中也增加影片偵測(Film Detection)和影像加強(Image Enhancement)的演算法設計，在這樣演算法的架構下，透過影片偵測的演算法，我們可真實地還原3:2 Pull Down的影片格式，而不會有鋸齒狀(Saw-Toothed)的畫面出現，而影像加強的演算法，則可以在解交錯後，經過影像的調整，使輸出畫面呈現不同的效果，達到消費者的需求。

In recent years, progressive scanning output devices have becoming very popular. However, many video sources are still using the conventional interlaced TV format. Therefore, the de-interlacing technique which converts interlaced picture to progressive picture is essential. It has been used widely in various kinds of commercial products. But the conventional simple de-interlacing method does not provide good picture quality particularly in the moving areas. The main theme of this thesis is an integrated de-interlacing system, which incorporates several known and improved techniques in a nice manner to produce good de-interlaced image quality. We first develop an accurate motion detector that classifies image regions into stationary, low-motion, and high-motion categories. The simple field merging method is applied to the stationary regions. The edge line average interpolation method is applied to the slow-motion regions. Finally, the motion-compensated interpolation is applied to the high-motion regions. In addition, hierarchical motion estimation and motion vector smoothing techniques are employed to enhance the quality of estimated motion vectors. Our computer simulation shows that the subjective image quality is improved by using the proposed scheme. Also, its PSNR measures are better than the conventional spatial or temporal interpolation schemes. In addition, in real applications, interlaced TV pictures are often derived from the films at different frame rate. To achieve a good picture quality, a film detector and an associated image enhancement scheme are added to our de-interlacing system. In this proposed system architecture, we can recover the 3:2 pull down format. With image enhancement algorithm after de-interlacing, the subjective image quality is generally improved.