用於消化道影像壓縮之簡化版H.264畫面內編碼器實現

Abstract

這篇論文的目標是發展一個專為膠囊內視鏡設計，極低功率消耗的影像壓縮處理器。在膠囊內視鏡的應用上，考慮內視鏡中電池功率消耗和影像品質的權衡是件非常重要的事。使用最先進的動態影像壓縮技巧能藉著它們的高壓縮率，明顯的減少位元數。但是它們都需要大量的計算和從電池中消耗大量的功率。用其他快速壓縮演算法來減少計算量，會造成與原來影像的失真。因此，這篇論文提出一個簡化版的H.264畫面內編碼器。利用腸胃道影像的特徵與膠囊內視鏡的規格，來做功率消耗與影像品質的取捨，選擇出最適合腸胃道影像之演算法。最後使用低功率架構來硬體實現。我們以TSMC 0.18-um製程實現的結果，發展的動態影像壓縮需要60K邏輯閘，在每秒兩張512x512大小的畫面下消耗功率為0.9161mW，同時壓縮比例能在4:1以下。

The objective of this thesis is to develop an ultra-low-power image compression processor for capsule endoscope or swallowable imaging capsules. In applications of capsule endoscope, it is imperative to consider battery life and performance trade-offs. Applying state-of-the-art video compression techniques may significantly reduce the image bit rate by their high compression ratio, but they all require intensive computation and consume much power from battery. There are many fast compression algorithms for reducing computation load; however, they may result in distortion of original image. Thus this thesis proposes a modified H.264 Intra-frame encoder for gastrointestinal image. The algorithm exploits the characteristic of gastrointestinal image to reduce compute complexity and save power. As the result of implementation, the developed video compressor costs 60k gates at 2 frames/sec, consumes 0.9161mW, while the compression ratio can be as low as 4:1.