使用色彩量化的影像電話編碼

Abstract

本篇論文提出一個簡單且快速的影像電話編碼方法，此方法主要由以下三 個部份所構成: 色彩量化、單張畫面的編碼以及運動量的估測。我們提出 兩種快速的色彩量化方法，用以降低位元率及運動量估測的時間，這兩種 方法以平均量化方法為藍本，並以局部統計來改進原先所設定的調色板。 本篇論文也提出兩種新的單張畫面編碼方法，由於此二種方法為區塊壓縮 的改良方法，它們也具有其良好的線路錯誤抵禦能力，因此適用於影像電 話編碼。在此我們也探究色彩量化如何用於運動量估測，以增快其速度。 如果兩個像素點的色彩指標相同則此二點被視為相合，而最相合的兩個區 塊為相合點最多的區塊。實驗結果顯示此方法用於影像電話編碼的可行性 。 Here we propose a simple and fast videophone coding which consists of three parts: color quantization, intraframe coding, and motion estimation. Two on-line algorithms for color image quantization are proposed to reduce the bit-rate and the computation time for motion estimation. These two algorithms are based on uniform quantization, and use the local statistics to refine the color palette. Two new intraframe coding algorithms are also proposed to remove the spatial redundancy in the still frame. Since the proposed algorithms are modifications of block truncation coding, they inherit the superior channel error resisting capability of block truncation coding, and are therefore suitable for videophone applications. The bit-rate of the image coded by the algorithms can be further reduced by using the color indices to preserve the color information. We also explore the motion estimation utilizing color quantization. Two pixels are regarded to be matching pixels if they have the same color index. The best- match block is therefore the block with most matching pixels. Good experimental results prove the feasibility of the proposed approaches to videophone applications .