标题: | 基于拉格朗日最佳化针对 H.264 画面内编码的位元率控制演算法 Lagrangian-Optimization based Intra Frame Rate Control for H.264/AVC |
作者: | 周鼎力 Chou, Ting-Li 蔡文锦 Tsai, Wen-Jiin 资讯科学与工程研究所 |
关键字: | 位元率控制;画面内编码;拉格朗日最佳化;预测模型;H.264;Rate control;intra frames;Lagrangian optimization;Prediction model;H.264 |
公开日期: | 2008 |
摘要: | 为了让视讯编码后的位元率能维持在频宽的限制之内,并且达到良好与稳定的画面品质,位元率控制是相当重要的。然而目前大多数的研究都集中在画面间编码(inter frames)而不是容易造成缓冲区溢位的画面内编码(intra frames)。此外Intra-only 这种编码方式也已经纳入H.264 新的profile 当中,它较传统GOP 编码更适合应用在特别要求画面品质的产品上。 在此论文中,我们提出一个于 Intra-only 编码与GOP 编码皆适用的位元率控制演算法。首先我们提出基于 Lagrangian 最佳化的 QP 决定方式,藉由位元率与 PSNR 预测模型,我们利用 Lagrangian 最佳化来找出可以平衡画面品质与编码效能的QP最佳解。另外,为了解决场景变换对位元率控制所产生的影响,在找出场景变换的画面后,针对其使用以梯度复杂度为基础的位元率模型来决定适合的QP,避免缓冲区溢位。实验结果显示,提出的方法可以达到更好更稳定的画面品质,且缓冲内含量也都维持在较低的水平。 Rate control serves as an important technique to constrain the bit rate of video transmission over a limited bandwidth and to control the bit allocations within a video sequence to maximize its overall visual quality. However, most of rate control researches focus on inter coding frames instead of intra coding frames which are more possible to cause buffer overflow problem. Besides, H.264 Intra-only compression scheme has been standardized as H.264 profiles which are more proper for professional applications than traditional GOP compression scheme. In this thesis, we propose an improved rate control scheme which is appropriate not only for GOP compression but also for Intra-only compression. First, we present a Lagrangian-optimization based QP determination scheme for I-frames. By the estimation models for rate and PSNR of I-frames, the est quantization parameters can be determined by Lagrangian optimization method. In order to deal with the specific intra frames caused by scene transitions, a gradient complexity based QP determination method is proposed. After detecting scene change frames, the proposed gradient complexity based rate-QS model is adopted to determine appropriate QPs for avoiding buffer overflow and saving bit budget. Simulation results show, that compared to other reference algorithms, our approach achieves better and stable quality with low buffer fullness. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079655537 http://hdl.handle.net/11536/43341 |
显示于类别: | Thesis |
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