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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/64537

    Title: 基於內容適應式模型之H.264/AVC快速演算法與位元率控制;Model-Based Fast Algorithm and Rate Control for H.264/AVC
    Authors: 吳靖宇;Wu,Ching-Yu
    Contributors: 資訊工程學系
    Keywords: H.264/AVC;畫面內預測;位元率控制;品質控制;失真-量化;位元率-量化;感興趣區域;H.264/AVC;Intra Prediction;Rate Control;Quality Control;Distortion-Quantization;Rate-Quantization;Region of Interest
    Date: 2014-05-05
    Issue Date: 2014-08-11 18:37:12 (UTC+8)
    Publisher: 國立中央大學
    Abstract: H.264/AVC影片編碼已經成為目前最常被使用的編碼標準,許多研究也因此致力於追求更高效率的影片編碼,以及維持良好的位元率-失真表現。在本篇論文中,我們研發了許多內容適應性的模型來加快H.264/AVC的編碼速度,以及達到更好的位元率和品質控制。



    最後,我們藉由估測失真與量化參數間的關係,進一步探討位元率控制以及品質控管問題。我們提出了一個內容適應性的失真-量化模型,來預測畫面或區塊的失真程度。和之前的位元-量化模型類似,該模型只有一個可使用巨區塊內容調整的參數,並且能在每張畫面被編碼之前,就先行預測該畫面的失真程度。在由訊噪比所定義的畫面品質被設定之後,該模型能夠幫助計算出適合的量化參數。藉由此模型,我們進一步探討兩個恆定畫質的影片編碼應用,希望能幫助相關專業應用,例如影片的儲存以及編輯,達到更好的品質與效果。;H.264/AVC has become the most frequently used video codec nowadays. A lot of efforts have been made to pursue highly efficient video coding and to maintain good rate-distortion performances of video compression. In this dissertation, several content-adaptive models are developed to increase the speed of video encoding and to achieve better rate/quality control in H.264/AVC. The dissertation consists of three major parts. First, an efficient intra-prediction mode decision mechanism is presented. A projection-based approach, which utilizes the reconstructed surrounding pixels and block content to compute the predicted block residuals (PBR), can effectively eliminate the less probable modes from the computation of Rate Distortion Optimization. According to the PBR and coding information acquired during the encoding process, some prediction modes and macroblock types can be further skipped to accelerate the intra coding. Then, after considering the efficiency of intra coding, we research the issue of Rate-Quantization (R-Q) in the intra coding of H.264/AVC. Assigning an appropriate Quantization Parameter (QP) to the intra-coded frames is very important to the video coding. A content-adaptive R-Q model is thus presented to predict the bit usage of intra-coded frames. The relationship between the QP of a macroblock and the block complexity is derived so that a suitable QP can be determined under a target bit-rate. Since the proposed model is built on macroblocks, Region of Interest (ROI) coding can also be achieved. By adjusting the QP value at the macroblock level, more bits can be assigned to the ROI to better preserve its perceptual quality. Finally, we tackle the problem of rate/quality control for regular video encoding by estimating the resultant quality or distortion associated with QP. A Distortion-Quantization (D-Q) model is proposed to predict the distortion level, which is defined as the difference between the original video frame and the decoded one in the sum of squared errors. As in the R-Q model, the proposed D-Q model also has only one adjustable parameter related to the macroblock content and provides a mapping between QP and the corresponding distortion before the exact encoding process. Given a targeted frame quality measured in peak signal to noise ratio (PSNR), this model helps to assign a suitable QP value to each frame. Two applications are then considered, i.e., the single-pass constant frame PSNR coding and the two-pass coding with the additional bitrate or storage constraint, both of which can facilitate such applications of video archiving and editing.
    Appears in Collections:[資訊工程研究所] 博碩士論文

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