最近這些年多媒體影音服務的應用發展越來越快速。被JVT所訂定的H.264/AVC是目前最新的國際視訊編碼標準。同時針對使用H.264/AVC的即時多媒體應用，編碼位元率控制也是一項極為重要的技術。為了克服這個課題，JVT採用了JVT-G012方案作為這項控制機制的主體並把它實作在H.264的模擬平台JM12.4。然而JVT-G012仍然存在了一些問題，其中包括了
(1)針對關鍵的 R-D Model，方案中使用的 MAD預測方式並不夠精確。
(2)針對高壓縮率的影音標準，方案中所使用的檔頭預測並不夠精確。
(3)錯誤延續的緩衝區控管技術導致實際緩衝區溢出的情況大幅上升。
因此為了解決上述問題本論文針對即時或是低延遲環境的視訊服務提出一個改良的編碼位元率控制機制。在此機制裡本論文將利用場景轉換偵測區分出不同的畫面特性，再利用INTER 16X16的移動向量來預測最適合的檔頭位元數以及MAD資訊，最後站在實際緩衝區的角度上對編碼位元率控制的分配機制進行限制。

In recent years, the application for multimedia services is increasing rapidly. H.264/AVC is the latest international video coding standard developed by the Joint Video Team (JVT) and rate control is an important technique in real time multimedia applications using H.264/AVC. In order to solve the issue, one rate control scheme JVT-G012 was adopted by JVT in the H.264 reference model JM12.4. However, there are some problems in the scheme, including
(1) For the important Rate – Distortion Model (R-D Model), the scheme use inaccurate mean absolute difference (MAD) prediction
(2) For high compression video standard, the scheme use inaccurate overhead bit estimation
(3) Inaccurate buffer control technique will cause the actual buffer overflow
In order to solve these above-mentioned problems, we present an adaptive rate control scheme for real time or low delay video communication. In the scheme, we present a scene change detection technique to demarcate the different scene characteristic. Then we use INTER 16X16 Motion Vector (MV) to predict the accurate overhead bits and the MAD. Finally we use improved buffer control technique to limit the frame-layer target bits.

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