共查询到19条相似文献,搜索用时 93 毫秒
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码率控制是视频编码中非常重要的技术之一,任何标准离开码率控制其应用都会受到限制.H.264/AVC是目前最新的视频编码标准,本文根据H.264/AVC编码标准的特性及其HRD部分对码率控制的要求,提出了一种新的适合H.264/AVC的码率控制算法,该算法实现了率失真优化与码率控制的结合,使得在达到码率控制的同时也能保证较高的编码效率,同时在码率控制的过程中根据HRD缓冲区状态进行位分配调整,保证了编解码缓冲区既不上溢又不下溢.该算法作为技术提案已被H.264/AVC接受,并集成到H.264/AVC的校验模型软件中. 相似文献
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码率控制是视频编码中的重要技术之一。本文在简要介绍传统的码率控制技术的基础上,着重分析和比较了H.264中的码率控制技术以及近年来提出的多种改进方法,并对H.264的码率控制方法提出了一些改进方向和建议。 相似文献
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本文详细讨论了H.264编码标准的码率控制结构,与MPEG-2的TM5模型进行了比较:并对JVT-G012提出的流量往返控制模型进行了探讨;最后对H264码率控制提出了一些改进意见。 相似文献
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本文基于ρ域线性率失真模型提出一种适用于H.264的帧级码率控制算法.先验证线性率失真函数对H.264编码算法的适用性,再通过使用混合自适应估计方法精确地估计出该模型惟一的参数θ,实现线性率失真函数在H.264码率控制中的应用.仿真结果表明,与JVT-H017算法相比,新算法不仅获得更精确的码率控制,而且获得更平稳的输出码率和PSNR,同时实现简单,适用于实时视频通信. 相似文献
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一种改进的H.264码率控制算法 总被引:2,自引:1,他引:1
码率控制是H.264视频编码中一项重要技术,对平稳码率和保证良好的图像质量起着重要作用.通过分析H.264 JVT-012中目标码率计算与分配算法的缺陷,提出了基于图像直方图和滑动窗技术的自适应改进方法.根据图像复杂度和场景切换,通过图像直方图和滑动窗引入比率因子λ,对预测的MAD进行自适应调整,使之更加接近真实的MAD值,从而有效地提高了码率控制的性能.实验结果表明,与JVT-G012算法相比,目标码率匹配更精确,图像解码质量提高且PSNR变化较小,并能较好地处理场景切换等问题. 相似文献
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H.264/AVC编码中的码率控制是通过有效控制输出码流的码率来提高其压缩视频质量的重要技术。本文基于H.264/AVC中的JVT-H017码率控制方案提出了一种改进算法。新算法根据H.264中DCT系数的分布特征,将柯西分布引入到码率控制模块,用更精确的柯西率失真模型取代了原先的二次率失真模型。在此基础上,进一步引入了一种联合PSNR比率和MAD比率进行图像复杂度预测的方法,并依此来调整帧级比特的分配和量化参数,克服了在出现复杂运动或场景切换时,因视频序列相邻帧之间相关性降低而导致的MAD预测失准的情况。实验结果表明,与JVT-H017方案及文献[5]中的算法比较,新的算法不仅具有更精确的码率控制,而且明显改善了输出码率的平稳性及重建图像的PSNR。 相似文献
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为了提高码率控制在视频编码中的性能,本文提出了一种新的帧层R-Q码率控制算法模型。该模型直接通过H.264码率进行量化控制,但没有考虑复杂度测量估计,从一定程度上提高了码率控制的准确性。通过大量的理论推导与实验验证,提出的模型明显提高了峰值信噪比(P S N R),提高了图像的质量。 相似文献
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This article presents an efficient rate control scheme for H.264/AVC video coding in low bit rate environment. In the proposed scheme, an improved rate-distortion (RD) model by both analytical and empirical approaches is developed. It involves an enhanced mean absolute difference estimating method and a more rate-robust distortion model. Based on this RD model, an efficient macroblock-layer rate control scheme for H.264/AVC video coding is proposed. Experimental results show that this model encodes video sequences with higher peak signal-to-noise ratio gains and generates bit stream closer to the target rate. 相似文献
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Liquan Shen Zhi Liu Zhaoyang Zhang Xuli Shi 《Journal of Visual Communication and Image Representation》2009,20(1):28-34
Since the current rate control schemes in H.264 do not have the capability of efficient frame-level bit allocation, the video quality varies significantly from frame to frame especially for sequences with sudden scene changes or high motion activities. To overcome the limitation of frame-level bit allocation, we improve H.264 rate control scheme using two tools, the incremental proportional–integral–differential (PID) algorithm and the frame complexity estimation. The incremental PID algorithm is first introduced to control the buffer and reduce the influence of the buffer abrupt fluctuation in the process of frame-level bit allocation. To reduce more video quality variations, the frame target bit allocation is also adjusted by frame complexity that is estimated by residual energy. Simulation results show that the proposed rate control scheme, without introducing expensive computational complexity, decreases the average standard deviation of video quality by 32.29%. 相似文献
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Hongtao Yu Zhiping Lin Feng Pan 《IEEE transactions on circuits and systems. I, Regular papers》2005,52(12):2707-2716
This paper aims at applying H.264 in medical video compression applications and improving the H.264 rate control algorithm with better perceptual quality. First, H.264 is briefly reviewed and introduced to the area of medical video compression. Second, a new motion complexity (MC) measure is defined to express the complexity of motion contents in a video frame, and a new H.264 rate control scheme with the MC measure and perceptual bit allocation is proposed for medical video compression. Third, two sets of experiments are conducted: the comparison between MPEG-4 and H.264, and the comparison between JVT-H014 , which is the H.264 adopted rate control algorithm, and our proposed rate control scheme. The first set of experiments shows that compared with MPEG-4, H.264 can achieve a significant average peak signal-to-noise ratio (PSNR) gain of up to 4.35 dB for the test medical video sequences, and thus is much more effective when applied in medical video compression. The second set of experiments shows that compared with H014, the proposed rate control scheme can achieve better perceptual video quality, with an average PSNR gain of up to 0.19 dB for the test medical video sequences. 相似文献
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Hierarchical B-frames can bring high coding performance when introduced into H.264/AVC.However,the traditional rate control schemes can not work efficiently in such new coding framework.This article presents a rate control algorithm for hierarchical B-frames in H.264/AVC.Taking the feature of the dyadic hierarchical coding structure into consideration,the proposed algorithm includes group of pictures(GOP)layer,temporal layer and frame layer bits allocation.After frame layer bits allocation is complete,frame layer quantization parameters(QP)determination strategy is responsible for calculating the final QP.Experimental results show that compared with other rate control algorithms,the proposed one can improve the coding performance and reduce the mismatch of target bit rate and real bit rate. 相似文献
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为在确保视频压缩码流平稳且带宽受限的情况下提升重建视频质量,本文针对使用Weibull密度分布对压缩视频序列率失真性能分析的方法,对其模型进行数学简化,并以帧层编码速率控制的缓冲器充盈度和重建视频质量为目标,提出了一种新的H.264压缩视频速率控制方法——帧比特分配算法。该算法以H.264的JM16.1为视频压缩编码平台,将简化率失真模型嵌入速率控制算法中,以一个GOP为控制单元对其内部各图像帧进行比特分配与调整,同时以帧为周期进行算法模型参数更新。实验结果表明,本文提出的算法要比JVT-H017的算法在重建视频客观质量(PSNR)方面平均有0.30dB的改善,并能够得到更加平稳质量的视频输出。在实际输出码率方面,本文算法比JVT-H017的算法更低,并且编码缓冲器充盈度较JVT-H017平稳且没有上下溢的情况出现。 相似文献
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《Signal Processing: Image Communication》2009,24(3):177-199
Hierarchical B-frames contribute to improvement of coding performance when introduced into H.264/AVC. However, the existing rate control schemes for H.264/AVC, which are mainly applied to IPPP and IBBP coding structures, cannot work efficiently for the coding structures with hierarchical B-frames. In this paper, a frame layer rate control scheme for hierarchical B-frames is proposed. Firstly, an adaptive starting quantization parameter (QP) determination method is implemented to derive the QP for the first coding frame based on the available channel bit rate and the content of the current video sequence. Then, the target bit budget for a group of pictures (GOP) is calculated based on the target bit rate and the buffer status. Afterwards, a temporal level (TL) layer rate control phase is introduced, and the GOP layer target bit budget is allocated to each TL. In the frame layer rate control phase, a method based on a rate-distortion model and the coding properties of the previous coded key frames is derived to determine the QP for the current key frame. For hierarchical B-frames, we introduce a typical weighting factor in the determination of their target bit budgets to address the features of the hierarchical coding structures. This weighting factor is calculated according to the target bit budget of the GOP layer and the knowledge obtained from the previous coded B-frames in each TL. Subsequently, the QP for coding the current B-frame is computed by a quadratic model with different model parameters for different TLs, and the computed QP is further adaptively adjusted according to the usage of the target bit budgets. After coding the current frame, an update stage, in which a threshold-based method is integrated to avoid model degradation, is invoked to update the parameters for rate control. Experimental results demonstrate that when the proposed rate control scheme is applied to the coding structure with hierarchical B-frames in H.264/AVC, the actual coding bit rates can match the target bit rates very well, and the encoding performance is also improved. 相似文献
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RATE CONTROL ALGORITHM FOR H.264 VIDEO ENCODER 总被引:1,自引:0,他引:1
Xue Jinzhu Shen Lansun 《电子科学学刊(英文版)》2003,20(6):456-460
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为提高H.264/AVC标准在带宽资源严重受限时的压缩效率,采用空时域相结合的编码思路,提出了一种基于运动检测的自适应抽帧方法,并结合空域下采样与重建研究了一种改进的H.264/AVC压缩性能优化框架。在编码端,原视频先空域下采样以减少空间分辨率,然后根据视频运动特征,采用不同抽帧模式自适应地降低帧率,再经H.264/AVC编码,有效降低了编码码率。在解码端,解码视频则采用与抽帧模式相对应的运动估计与补偿插帧方法重建出抽取帧,再利用超分辨率重建技术将视频恢复到原空间分辨率。实验结果表明,所提方法在低码率段的视频压缩性能优于H.264/AVC标准编解码及相关文献方法。 相似文献
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JVT-H017是H.264视频编码标准中采用的码率控制算法提案,但在许多实时场景应用中该算法还存在平均绝对差值(MAD)预测不准确等一些不足.针对现有码率控制技术的缺陷,提出一种改进的基本单元层码率控制算法.一方面在基于图像复杂度和运动信息的基础上采用了4种时空加权模型预测平均绝对差值,并且采用运动矢量信息对图像复杂程度进行判定;另一方面结合MAD的变化情况分配目标比特.实验结果表明,相比于JVT-H017和一些新的文献算法,改进算法的编码图像峰值信噪比得到了提高,同时实际码率更接近于目标码率,码率控制性能更优越. 相似文献