共查询到20条相似文献，搜索用时 31 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
2.
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
3.
1 Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｔｈｅｉｎｔｅｒｅｓｔｉｎｖｅｒｙｌｏｗｂｉｔ ｒａｔｅｖｉｄｅｏｃｏｄｉｎｇｈａｓｉｎ ｃｒｅａｓｅｄｃｏｎｓｉｄｅｒａｂｌｙｗｉｔｈｔｈｅｃｒｅａｔｉｏｎｏｆｎｅｗｓｅｒｖｉｃｅｓａｎｄａｐｐｌｉｃａｔｉｏｎｓｒｅｑｕｉｒｉｎｇｔｈｉｓｃｌａｓｓｏｆｂｉｔｒａｔｅｓｉｎｔｈｅｉｒｆｕｎｃｔｉｏｎ .Ｗｉｔｈｔｈｉｓｔｒｅｎｄ ,ｏｂｊｅｃｔ ｏｒｉｅｎｔｅｄｖｉｄｅｏｃｏｄｉｎｇｗａｓｆｉｒｓｔｐｒｏｐｏｓｅｄｂｙＭｕｓｍａｎｎｅｔａｌ.ｉｎ 1989[1 ],ａｎｄｈａｓｂｅｅ… 相似文献
4.
１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｌｉｍｉｔｅｄｔｒａｎｓｍｉｓｉｏｎｂａｎｄｗｉｄｔｈａｖａｉｌａｂｌｅｏｎｃｕｒｒｅｎｔｃｏｍｍｕｎｉｃａｔｉｏｎｃｈａｎｎｅｌｓｓｕｃｈａｓｐｕｂｌｉｃｓｗｉｔｃｈｅｄｔｅｌｅｐｈｏｎｅｎｅｔｗｏｒｋｓ（ＰＳＴＮ... 相似文献
5.
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
6.
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
7.
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
8.
Asymmetric stereoscopic video coding can take advantage of binocular suppression in human vision by representing one of the two views in lower quality.This paper proposes a bit allocation strategy for asymmetric stereoscopic video coding.In order to improve the accuracy of bit allocation and rate control in the left view,a proportionalintegral-derivative controller is adopted.Meanwhile,to control the quality fluctuation between consecutive frames of the left view,a quality controller is adopted.Besides,a fuzzy controller is proposed to control the variation in quality between the left and right views by comparing the PSNR disparity of two views with a fixed threshold,which is used to quantize the binocular psycho-visual redundancy and adjust the quantization parameter (QP) of the right view correspondingly.The proposed algorithm has been implemented in H.264/AVC video codec,and the experimental results show its effectiveness in rate control while keeping a good quality for the left view,and fewer bits are allocated for the right view so that the overall bit rate is saved by 7.2% at most without the loss of subjective visual quality for stereoscopic video. 相似文献
9.
The existing H.264/AVC rate control schemes rarely include the perceptual considerations. As a result, the improvements in visual quality are hardly comparable to those in peak signal-to-noise ratio （PSNR）. In this paper, we propose a perceptual importance analysis scheme to accurately abstract the spatial and temporal perceptual characteristics of video contents. Then we perform bit allocation at macroblock （MB） level by adopting a perceptual mode decision scheme, which adaptively updates the Lagrangian multiplier for mode decision according to the perceptual importance of each MB. Simulation results show that the proposed scheme can efficiently reduce bit rates without visual quality degradation. 相似文献
10.
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
11.
INTRODUCTION The technology of smart or adaptive antennawhich can increase capacity and range, and reducesmultipath propagation of mobile radio communi-cation system, has aroused great interest in recentyears (Haardt and Spencer, 2003; Bellofiore, 2002;Godara, 1997). Beamforming is a key technologyin smart antenna systems (SAS) and many differentadaptive beamforming algorithms have been pro-posed. Code division multiple access (CDMA)system will be applied in most mobile communi-… 相似文献
12.
The paper presents a modified least squares despread respread multitarget constant modulus algorithm(LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate(MBER)criterion.The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate(BER)of code division multiple access(CDMA)mobile communication system. In order to achieve adaptive update of weight vectors,a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance,capacity and near-far effect resistance of a given CDMA communication system. 相似文献
13.
LIU Yun-qiang YU Song-yu WANG Xiang-wen ZHOU Jun 《浙江大学学报(A卷英文版)》2006,7(4):543-548
INTRODUCTION Many emerging video applications, such as video-on-demand (VOD) and distance learning, rely on the efficient transfer of compressed video. For the same average bandwidth, variable bit rate (VBR) encoded video streams have higher perceivable qual- ity and greater opportunity for statistical multiplexing gains compared to constant bit rate (CBR) video streams (McManus and Ross, 1996). However, VBR video typically shows significant burstiness on mul- tiple time scales, due … 相似文献
14.
INTRODUCTION H.264 (Wiegand et al., 2003) is the latest video coding standard developed by the ISO/IEC Moving Picture Experts Group (MPEG) and the ITU-T Video Coding Experts Group (VCEG). Besides many new technologies which can bring high compression effi-ciency, H.264 also provides other tools to flexibly adapt to different transmission networks, such as flexible macroblock ordering (FMO) (Wenger and Horowitz, 2002a; 2002b) for dealing with data er-rors/losses in error prone… 相似文献
15.
Motion estimation is an important part of the MPEG-4 encoder, due to its significant impact on the bit rate and the output quality of the encoder sequence. Unfortunately this feature takes a significant part of the encoding time especially when the straightforward full search(FS) algorithm is used. In this paper, a new algo-rithm named diamond block based gradient descent search (DBBGDS) algorithm, which is significantly faster than FS and gives similar quality of the output sequence, is proposed. At the same time, some other algo-rithms, such as three step search (TSS), improved three step search (ITSS), new three step search (NTSS),four step search (4SS) , cellular search (CS) , diamond search (DS) and block based gradient descent search (BBGDS) , are adopted and compared with DBBGDS. As the experimental results show, DBBGDS has its own advantages. Although DS has been adopted by the MPEG-4 VM, its output sequence quality is worse than that of the proposed algorithm while its complexity is similar to the proposed one. Compared with BBGDS, the proposed algorithm can achieve a better output quality. 相似文献
16.
ZHANG Zhao yang GAO Lei ZHANG Ying CHEN Hao 《上海大学学报(英文版)》1999,3(3):208-213
１ Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｉｎｉｍａｇｅｃｏｍｐｒｅｓｓｉｏｎｃｏｄｉｎｇｓｃｈｅｍｅｓ,ｖａｒｉｏｕｓｉｍａｇｅｃｏｄｉｎｇｔｅｃｈｎｉｑｕｅｓｓｕｃｈａｓｔｒａｎｓｆｏｒｍｃｏｄｉｎｇｈａｖｅｂｅｅｎｄｅｖｅｌｏｐｅｄ．Ｗｈｉｌｅｔｈｅｓｅｔｅｃｈｎｉｑｕｅｓｈａｖｅｌｅｄｔｏｒｅｌａｔｉｖｅｌｙｈｉｇｈｑｕａｌｉｔｙｒｅｃｏｎｓｔｒｕｃｔｅｄｉｍａｇｅｓａｔｂｉｔｒａｔｅｓａｒｏｕｎｄ１．０ｂ／ｐｉｘｅｌｏｒｍｏｒｅ,ｔｈｅｙｓｏｍｅｔｉｍｅｓｐｒｏｄｕｃｅｓｐｅｃｉｆｉｃｔｙｐｅｏｆ… 相似文献
17.
为了提高水印的综合效果,根据多小波变换后相邻系数之间具有很强的相关性的特点,提出了一种基于支持向量机的图像水印算法.由于支持向量机在小样本训练的情况下具有良好的学习和泛化能力.因此,可以首先利用支持向量回归机建立相邻系数之间的关系模型.然后,通过调整模型的输入来嵌入或提取水印.实验结果表明,用算法得到的水印不但具有很好的图象感知质量,而且鲁棒性好,实用性强. 相似文献
18.
针对萤火虫群优化(GSO)算法在解决全局优化问题时出现的易陷入局部最优、收敛速度慢、求解精度不高等问题,提出一种改进的混沌萤火虫群优化(ICGSO)算法,修改了GSO算法动态决策域半径更新公式,并采用自适应动态步长,引入混沌优化算法提高局部搜索能力。实验结果表明将ICGSO算法应用于建立在神经网络预测模型上的瓦斯突出预测中的有效性。 相似文献
19.
Cognitive radio (CR) is a promising technology deemed to improve the efficiency of spectrum utilization. This paper considers
a spectrum underlay cognitive radio network, in which the cognitive users (CUs) are allowed to use the radio spectrum concurrently
with the primary users (PUs) under the interference temperature constraint. We investigate the system performance by using
the proposed joint channel and power allocation scheme under two transmit strategies to achieve higher data rates and performance
diversity gain respectively. Simulation results show that the proposed scheme provides a significant improvement on the bit
error rate (BER) performance and spectrum efficiency of a cognitive wireless network. 相似文献
20.
INTRODUCTION Unitary space-time modulation (USTM) (Hochwald and Marzetta, 2000) has been shown to be ideally suited for Rayleigh flat fading channels when there is no CSI. And for continuously changing fading channels, differential unitary space-time modulation (DUSTM) was proposed in Hochwald and Sweldens (2000). However, the performance of DUSTM de-grades considerably in frequency-selective fading channels often encountered in broadband wireless communications. Hence concatena… 相似文献