為穩定Motion JPEG2000視訊品質的兩階段串流緩衝控制

TWO-STAGE BUFFER CONTROL FOR CONSTANT QUALITY TRANSMISSION OF MOTION JPEG2000 VIDEO STREAM

陳科維(Ke-Wei Chen)

指導教授 ： 周俊賢

大同大學/電機資訊學院/通訊工程研究所/碩士(2007年)

摘要

近年來Motion JPEG2000(MJP2)逐漸受到矚目，是因為Motion JPEG2000在intra-frame編碼上具有很高的效率，且在具有封包遺失的網路和時變通道上傳輸串流壓縮資料上有極高的效果。MJP2 是 JPEG2000影像編碼標準的延伸。MJP2實際上是將baseline JPEG2000所壓縮的資料編織成一串流格式。如同影像編碼器，雖然編碼串流的格式已被明確定義，但是實現MJP2的編碼器上還有一些須要解決的問題。在這些問題之中，如何在變動的視訊內容和通道頻寬不變動下減少視訊品質的變動是較重要的。與位元率控制有關的運算複雜度，以及在實現上必須合乎成本效益的記憶體使用量和與編碼運算有關的低時間延遲都是要被克服的難題。
在本篇論文中，是提出一個二階段的MJP2編碼上新穎的暫存器控制演算法，此方法可以有效的去減少視訊品質的變動性和記憶體需求。在第一階段，先從已經傳送出的畫面，以及還存放在緩衝器中畫面和正在傳送中的畫面，計算出一個平均的失真值，經由平均失真值，初步的分配資料量給每一個畫面。在第二階段中，計算經由第一階段後全部畫面所分配的位元數，是否超過可變的傳送緩衝器。在這個演算法中，只需用很少的畫面緩衝器就可以在，有限的位元下維持視訊品質。
我們的目標是希望，在有限的頻寬下分配給所有的畫面而使得每一個畫面可以得到一個近似相同的畫面品質。模擬結果顯示出，我們所提出演算法跟原始Motion JPEG2000的方法，比較下在穩定視訊品質上可以得到較好的效率。

關鍵字

位元率控制，緩衝器控制，動態JPEG 2000，編碼截斷點，位元率對失真曲線。

並列摘要

Motion JPEG2000 (MJ2) has recently received increasing attention for its high efficiency in intra-frame coding and salient features in streaming compressed data over lossy networks and time-varying channels. As an extension of the JPEG2000 image coding standard, MJP2 is virtually a stream format for organizing compressed frames generated by the baseline JPEG2000 coding engine. As in the case of image coder, MJP2 has also some unsolved problems in the implementation of coder even though the generation of code streams is clearly specified. Among these problems, the buffer control for reducing quality fluctuation across frames under changing content and varying channel bandwidth is most significant.
In this thesis, a novel buffer control algorithm for MJP2 coding, which consists of two stages, is proposed to efficiently reduce quality fluctuation and memory usage. In the first stage, an average of distortion is computed from the frames that have already transmitted, the frame in transmission and the frames in transmission buffer which video frames to get consistent distortion. In the second stage, the overall bit number allocated in the first stage should not exceed the available space in the transmission buffer. In the algorithm, the lowest number of video frame buffers required for maintaining video quality at a given bit rate can be achieved.
The goal is to allocate the capacity of channel between sequences to achieve constant quality across all sequence. Experimental results show that the proposed buffer control algorithm has higher performance in constant quality transmission than Motion JPEG2000 without buffer control.

並列關鍵字

truncation point ； Motion JPEG2000 ； buffer control ； rate control ； rate-distortion curve

參考文獻

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