共查询到20条相似文献，搜索用时 80 毫秒
1.
Concerning inter4v mode employed widely in MPEG-4 video, a new temporal error concealment scheme for MPEG-4 video sequences is proposed, which can selectively interpolate one or four motion vectors (MVs) for the missing macroblock (MB) according to the estimated MB coding mode. Performance of the proposed scheme is compared with the existing schemes with multiple testing sequences at different bit error rates. Experimental results show that the proposed algorithm can mask the impairments caused by transmission errors more efficiently than 0 MV and average MV methods by consuming more time for different bit error rates. It has an acceptable image quality close to that obtained by the selective motion vector matching (SMVM) algorithm, while taking less than half of cycles of operations. The proposed concealment scheme is suitable for low complexity video real-time implementations. 相似文献
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YIN Ming WANG Hong-yuan 《浙江大学学报(A卷英文版)》2006,7(6):990-995
INTRODUCTION Rate control has been playing an increasing important role in real-time video communication. An encoder employs rate control to regulate output bit- streaming to meet certain channel bandwidth and buffer constraints while pursing high video quality. One fundamental problem in the encoder design is the selection of quantization parameter (QP) to maximize visual quality under constraints imposed by the computational complexity, delay, bandwidth and/or loss factors. At present… 相似文献
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Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality. 相似文献
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HOU Wei dong MO Yu long 《上海大学学报(英文版)》1999,(4)
１ Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｔｈｅｐｕｂｌｉｃｓｗｉｔｃｈｅｄｔｅｌｅｐｈｏｎｅｎｅｔｗｏｒｋ（ＰＳＴＮ）ａｎｄｉｔｓｂｒｏａｄｃｏｖｅｒａｇｅｐｒｏｍｏｔｅｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｖａｒｉｏｕｓｖｉｓｕａｌｃｏｍｍｕｎｉｃａｔｉｏｎｓｓｅｒｖｉｃｅｓｏｖｅｒＰＳＴＮ［１］．ＴｈｅａｌｌｏｗｅｄｂｉｔｒａｔｅｏｖｅｒＰＳＴＮｗｉｔｈｖｏｉｃｅｂａｎｄｍｏｄｅｍｉｓｓｔｉｌｌｌｉｍｉｔｅｄｔｏｌｏｗｅｒｔｈａｎ６４ｋｂｉｔ／ｓ,ｗｈｉｃｈｐｒｅｓｅｎｔｓａｇｒｅａｔｃｈａｌｌｅｎｇｅ… 相似文献
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１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｌｉｍｉｔｅｄｔｒａｎｓｍｉｓｉｏｎｂａｎｄｗｉｄｔｈａｖａｉｌａｂｌｅｏｎｃｕｒｒｅｎｔｃｏｍｍｕｎｉｃａｔｉｏｎｃｈａｎｎｅｌｓｓｕｃｈａｓｐｕｂｌｉｃｓｗｉｔｃｈｅｄｔｅｌｅｐｈｏｎｅｎｅｔｗｏｒｋｓ（ＰＳＴＮ... 相似文献
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It is worth to mention that Eq.（19） can be found alternatively first by describing the boundary conditions at each of the sampling points to obtain a set of linear equations with respect to the modal coefficients Then, determining the number of sampling points in order that the number of linear equations be twice the number of unknowns 相似文献
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针对AdHoc网络的视频传输,提出了一种新的网络带宽预测及控制方案．该方案基于跨层、接收端反馈以及贝叶斯网络等技术．对视频传输过程进行公式化描述,从而推导出影响视频传输质量的几个主要因素,这些因素可以通过跨层机制或接收端反馈的方式获取．根据这些影响因素,确定变量集和贝叶斯网络拓扑结构,从而构建贝叶斯网络预测模型．预测结果作为AdHoc网络带宽,根据该带宽值来控制视频编码器,动态调节输出的实时视频流码率．为验证该方案,对整个视频通信系统进行了仿真．结果显示,跟传统的传输方案相比较,夺方案能更好地利用网络带宽,减少了数据包的丢失,提高了实时视频质量． 相似文献
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We propose a novel prioritized intra refresh method for the wireless video communication. The proposed method considers the characteristics of the human visual system, the error-sensitivity of the bitstream, and the state of the time-varying wireless channel jointly. An expected perceptual distortion model was used to adjust the intra refresh rate adaptively. This model consists of the perceptual weight map based on an attention model, the bit error probability map based on bitstream size, and the dynamic channel state information （CSI）. Experimental results indicate that, compared with other intra refresh methods that consider only the content of the video or the CSI, the proposed method improves the average peak signal-to-noise ratio （PSNR） of the whole frame by about 0.5 dB, and improves the average PSNR of the attention-area by about 0.8 dB. 相似文献
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Variable size motion estimation (ME) and disparity estimation (DE) are employed to select the best coding mode for each macroblock (MB) in the current joint multiview video model (JMVM).This technique achieves the highest possible coding efficiency,but it results in extremely large computation complexity which obstructs the multiview video coding (MVC) from practical application.This paper proposes an adaptive early termination of fast mode decision algorithm for MVC.It makes use of the coding information o... 相似文献
12.
徐巍 《咸阳师范学院学报》2007,22(5):74-77
人类不同历史时期传播媒介的变化所带来的是不同文化的变迁。口语文化是一种"听"的文化,印刷文化是一种"读"的文化,而视觉文化则是一种"看"的文化。视觉文化与印刷文化的不同主要表现在以下方面:它们的主因分别是语言文字与视觉图像;在思维存在方式上,二者表现为理性思辨与感性直觉的差异;它们所代表的文化立场分别是精英文化与大众文化。由于视觉文化的通约性特征,与印刷文化相比确实有很大的优势,它迎合了全球化的趋势,满足了人与人密切交往的时代要求。但它同时也造成了优势文化的意识形态传播和垄断,势必对各国文化带来新的影响。 相似文献
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INTRODUCTION Low latency video transmission is very de manding in terms of the performance of all layers i the protocol stack. Over the last decade, research ha focused on enhancements of each individual laye without considering cross-layer interactions. Adapt ing video coding to the channel/network condition and technologies (and vice versa) (Girod et al., 2002 via the cross-layer exchange of information has onl recently been investigated. van der Schaar et al.(200 developed a cross-laye… 相似文献
14.
政府决策面临的网络化挑战及对策 总被引：1，自引：0，他引：1
马煜 《沈阳教育学院学报》2004,6(4):98-100
政府上网意味着政府将实现一种全新的管理模式。那么，网络技术在与行政决策到结合中，相应地会给行政决策带来许多困难和问题，从而使行政决策面临新的挑战。对此，我们要给予足够的重视并制定相应的对策。 相似文献
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CHOU Philip A 《浙江大学学报(A卷英文版)》2006,7(5):737-748
INTRODUCTION Many applications, such as software distribution, Internet TV/video streaming, video conferencing, multiplayer gaming, personal media distribution and P2P web content duplication, distribute the same content from one source node to many destination nodes. For these applications, IP multicast is an ideal network layer solution. A distribution tree rooted at the source can be formed to reach an arbitrary number of receivers. During content distribution, every single piece of… 相似文献
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INTRODUCTION In typical video transmission systems, a video signal is compressed, and the resulting bit stream is transmitted over an error-prone channel. The errors may consist of symbol errors caused by fading, as observed for wireless channels, or packet erasures caused by congestion, as observed in the Internet. If a received video packet contains errors, then the portion of the video signal contained in the packet is lost and must be concealed. Error concealment schemes alone cannot … 相似文献
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Hou Weidong Mo Yulong Wei Chunlong 《上海大学学报(英文版)》1998,2(4):270-274
ｖｅｌｅｔ ＴｒａｎｓｆｏｒｍTX１ＩｎｔｒｏｄｕｃｔｉｏｎＶｉｄｅｏｃｏｍｍｕｎｉｃａｔｉｏｎｉｓｂｅｃｏｍｉｎｇｉｎｃｒｅａｓｉｎｇｌｙｉｍ－ｐｏｒｔａｎｔｉｎａｐｐｌｉｃａｔｉｏｎｔｏｓｅｖｅｒａｌａｒｅａｓｓｕｃｈａｓｔｅｌｅ－ｃｏｎｆｅｒｅｎ... 相似文献
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With advanced prediction modes of intra prediction, intra coding of H.264/AVC offers significant coding gains compared with previous video coding standards. It uses an important tool called Lagrangian rate-distortion optimization (RDO) technique to decide the best coding mode for a block, but the computational burden is extremely high. In this paper, we proposed an improved fast intra prediction algorithm including block type selection and mode decision algorithm based on analysis of edge feature of a block. Our algorithm filters out unlikely block type and candidate modes to reduce the RDO calculations. Experimental results showed that the proposed algorithm can reduce the computation complexity of intra prediction from 52.90% to 56.31%, with 0.04 dB PSNR degradation and 2% increase of bit rate. 相似文献
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1 Introduction The emerging H.264/AVC video coding standard hasbeen developed and standardized collaboratively byboth ITU-T VCEG and ISO/IEC MPEG organizations .As the newest international video coding standard ,H.264/AVC represents a number of advances i… 相似文献
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In this paper, a fast mode decision algorithm for inter macroblocks in H.264/AVC is proposed, The algorithm is able to classify all modes by both gradient operator and comparison of space-time correlation. Because only part of modes is used to compare with each other the computational complexity can be reduced greatly. The simulation results show that it takes about 75 % of encoding time for other algorithm with similar visual quality. 相似文献