- 學位論文
對可伸展式視訊編碼之最佳碼率分配
Optimal Rate Allocation for Scalable Video Coding
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摘要
我們在可伸縮視頻編碼中考慮了每個使用者對於不同解析度的偏好。並且根 據這些用戶的偏好，我們制定並解決基於小波變換的可伸縮視頻編碼和 H.264/SVC 的位元分配問題。首先我們考慮基於小波變換的視頻編碼器的位元分 配方法。我們提出了三種方法來解決位元分配的問題。首先是使用拉格朗日的高 效率方法來解決優化問題上限，其二是效率較低的動態規劃法，但其可以得到問 題的最佳解。這兩種方法都需要先了解用戶的喜好。對於未知用戶喜好的情況下， 我們用最小化最大失真法來解決問題。我們發現，最糟糕的表現往往發生在所有 的用戶都訂閱相同的解析度的時候。因此，最小化最大失真法與小波編解碼器傳 統的位元分配方法相同。根據我們進行多次的實驗，這些實驗分別考量了各種用 戶的偏好，結果表明，了解用戶的喜好顯著提高的可伸縮視頻編解碼器的編碼性 能。H.264/SVC 的位元分配問題要複雜得多，我們必須了解並分析H.264/SVC 多層編碼結構造成的失真。在這篇論文中，我們具體地分析了用於實現時間 (temporal)，空間(spatial)和質量(quality)的可伸縮視頻編碼（SVC）的編碼結構，並且根據分析的結果，提出了兩個對於失真-碼率線（R-D Curve）的優化算法：其一是已知用戶偏好的最優化演算法，另一個是最小化最大失真法。與目前最先進的位元分配法相較，當用戶的偏好都是已知的時候，我們的演算法在壓縮效率上有著顯著的改進。這篇論文中，我們對可伸縮視頻編碼提出了用戶偏好的概念，並在兩個最常見的可伸縮性視頻編碼方法中解決相應的位元分配問題。它們分別是，MCTF-EZBC 基於小波編碼器和H.264/SVC。在比較已知使用者偏好方法與未知使用者偏好方法的效能之後，我們亦驗證了可伸縮視頻編碼中用戶偏好的重 要性。
並列摘要
The scalable video coding problem is investigated, and based on the preferred resolution, the bit allocation problems of wavelet-based scalable video coding and H.264/SVC are formulated and solved. For the wavelet-based video encoder, three methods are proposed. The first is an efficient Lagrangian-based method that solves the upper bound of the problem optimally, and the second is a less efficient dynamic programming method that solves the problem optimally. Both methods require knowledge of the user preference on resolution. For the case where the user preference is unknown, we solve the problem by a min-max approach. Our objective is to find the bit allocation solution that maximizes the worst possible performance. We show that the worst performance occurs when all users subscribe to the same spatial, temporal, and quality resolutions. Thus, the min-max solution is exactly the same as the traditional bit allocation method for a non-scalable wavelet codec. We conduct several experiments on the 2D+t MCTF-EZBC wavelet codec with respect to various subscriber preferences. The results demonstrate that knowing the user preferences improves the coding performance of the scalable video codec significantly. For the rate allocation problem of H.264/SVC, we present a theoretical analysis of the distortion in multiple layer coding structures. Specifically, we analyze the prediction structure used to achieve temporal, spatial, and quality scalabilities in a scalable video coding (SVC), and show that the average peak-signal-to-noise (PSNR) of SVC is a weighted combination of the bit rates assigned to all the streams. We propose two rate-distortion (R-D) optimization algorithms: one employs the known user preference, and the other is based on the min-max approach which assumes the least favorable prior of the user preference. We compare the performance of our algorithms with that of a state-of-the-art scalable bit allocation algorithm and demonstrate that they outperform the compared approach when the user preference is known to both coders. In this Dissertation, we propose the concept of the user preference in the scalable video coding, and solve the corresponding rate allocation problems for the two most prevalent scalable video coding methods, which are the MCTF-EZBC wavelet based encoder and H.264/SVC. After comparing the coding gains of the methods with complete preference information over those with incomplete preference information, we verify the importance of the user preference in the scalable video coding.
參考文獻
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