共查询到20条相似文献，搜索用时 718 毫秒
1.
INTRODUCTION With the emergence of wireless technology, various multimedia services, e.g., audio and/or video, are reaching us today through portable devices any- time, anywhere and even more increasingly accessi- ble in the near future. High quality video streaming over wireless IP is one of the most attractive applica- tions by ongoing deployment of wireless local area network (WLAN) hotspots and even powerful Wi- MAX mobile coverage. However, the present Internet is not providing a… 相似文献
2.
INTRODUCTION Communication networks are growing quickly. Throughput, delays and losses become unpredictable because of heterogeneity and congestion. This results in lack of quality of service. Today’s solution is based on standard video codecs (as MPEG-2) that do not allow scalability and yield low quality at low bit-rates, complex forward error correction (FEC) codes that are not easily used with time-varying channels and must be set to face the worst case, and automatic repeat re- q… 相似文献
3.
ZHU Xiao-liang YANG Zong-kai DU Xu CHENG Wen-qing 《浙江大学学报(A卷英文版)》2006,7(10):1702-1708
INTRODUCTION Video streaming applications generally require continuous high bandwidth guarantees as well as stringent bounds on delays and jitters (Shen et al., 2004; Hassan and Krunz, 2004). Providing video streaming with acceptable quality degradation over wireless channels is fraught with challenges due to the adverse influence of bandwidth limitation, time variation, high error rate, and so on (Etoh and Yo- shimura, 2005; Shen et al., 2004; Chen and Zakhor, 2004; Hassan and Krunz, … 相似文献
4.
Classical unequal erasure protection schemes split data to be protected into classes which are encoded independently. The unequal protection scheme presented in this paper is based on an erasure code which encodes all the data together according to the existing dependencies. A simple algorithm generates dynamically the generator matrix of the erasure code according to the packets streams structure, i.e., the dependencies between the packets, and the rate of the code. This proposed erasure code was applied to a packetized MPEG4 stream transmitted over a packet erasure channel and compared with other classical protection schemes in terms of PSNR and MOS. It is shown that the proposed code allows keeping a high video quality-level in a larger packet loss rate range than the other protection schemes. 相似文献
5.
一种新的无线视频传输帧内刷新策略 总被引：1，自引：0，他引：1
首先分析了无线信道突发性出错和二阶Markov无线信道模型. 根据该模型和视频编码器的编码方式推导了突发性出错引起的帧内编码和帧间编码的信道失真. 然后提出了一种新的速率失真率(R-D)框架内的帧内刷新策略. 该策略一方面对无线视频传输系统的容错性能和编码效率进行了优化, 另一方面可有效阻止帧间错误传播, 减小信道失真. 在不同传输信道中的仿真结果验证了该策略在无线视频传输容错方面的性能改进. 相似文献
6.
LIU Hao ZHANG Wen-jun YANG Xiao-kang 《浙江大学学报(A卷英文版)》2006,7(10):1695-1701
INTRODUCTION In the encoding or transcoding of video stream- ing, intra refresh is introduced as a non-normative error-resilience tool. Although the intra-refresh schemes based on the rate-distortion optimization (C?té et al., 2000; Stockhammer et al., 2002) are superior to the early heuristic intra-refresh strategies, these new schemes cannot yet accurately estimate the video distortion due to time-varying packet losses, and usually ignore the inter-frame error-propagation effect. Chiou… 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.
We present an unequal decoding power allocation （UDPA） approach for minimization of the receiver power consumption subject to a given quality of service （QoS）, by exploiting data partitioning and turbo decoding. We assign unequal decoding power of forward error correction （FEC） to data partitions with different priority by jointly considering the source coding, channel coding and receiver power consumption. The proposed scheme is applied to H.264 video over additive white Gaussion noise （AWGN） channel, and achieves excellent tradeoff between video delivery quality and power consumption, and yields significant power saving compared with the conventional equal decoding power allocation （EDPA） approach in wireless video transmission. 相似文献
9.
在简要介绍蓝牙协议数据传输分组的基础上 ,对不同分组的数据传输能力进行了详细的分析 ,得出在一定的误码率环境下最适合数据传输的分组 同时提出利用BCH编码替代原有的编码的方案 ,在不降低最大数据传输能力的基础上 ,有效的提高了蓝牙的抗干扰能力 相似文献
10.
源认证是多播安全与群组安全中的基本问题,覆盖多播是当前的研究热点．基于哈希链和层次传递的思路提出了一个针对覆盖多播的源认证方案（SASOM）,对此方案的安全性和效率进行了分析． 相似文献
11.
１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｌｉｍｉｔｅｄｔｒａｎｓｍｉｓｉｏｎｂａｎｄｗｉｄｔｈａｖａｉｌａｂｌｅｏｎｃｕｒｒｅｎｔｃｏｍｍｕｎｉｃａｔｉｏｎｃｈａｎｎｅｌｓｓｕｃｈａｓｐｕｂｌｉｃｓｗｉｔｃｈｅｄｔｅｌｅｐｈｏｎｅｎｅｔｗｏｒｋｓ（ＰＳＴＮ... 相似文献
12.
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
13.
In this work, we present an evaluation of the performance and error robustness of RTP-based broadcast streaming of high-quality high-definition (HD) H.264/AVC video. Using a fully controlled IP test bed (Hillestad et al., 2005), we broadcast high-definition video over RTP/UDP, and use an IP network emulator to introduce a varying amount of randomly distributed packet loss. A high-performance network interface monitoring card is used to capture the video packets into a trace file. Purpose-built software parses the trace file, analyzes the RTP stream and assembles the correctly received NAL units into an H.264/AVC Annex B byte stream file, which is subsequently decoded by JVT JM 10.1 reference software. The proposed measurement setup is a novel, practical and intuitive approach to perform error resilience testing of real-world H.264/AVC broadcast applications. Through a series of experiments, we evaluate some of the error resilience features of the H.264/AVC standard, and see how they perform at packet loss rates from 0.01 % to 5%. The results confirmed that an appropriate slice partitioning scheme is essential to have a graceful degradation in received quality in the case of packet loss. While flexible macroblock ordering reduces the compression efficiency about 1 dB for our test material, reconstructed video quality is improved for loss rates above 0.25%. 相似文献
14.
Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models. 相似文献
15.
Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models. 相似文献
16.
In this work, we present an evaluation of the performance and error robustness of RTP-based broadcast streaming of high-quality high-definition (HD) H.264/AVC video. Using a fully controlled IP test bed (Hillestad et al., 2005), we broadcast high-definition video over RTP/UDP, and use an IP network emulator to introduce a varying amount of randomly distributed packet loss. A high-performance network interface monitoring card is used to capture the video packets into a trace file. Purpose-built software parses the trace file, analyzes the RTP stream and assembles the correctly received NAL units into an H.264/AVC Annex B byte stream file, which is subsequently decoded by JVT JM 10.1 reference software. The proposed measurement setup is a novel, practical and intuitive approach to perform error resilience testing of real-world H.264/AVC broadcast applications. Through a series of experiments, we evaluate some of the error resilience features of the H.264/AVC standard, and see how they perform at packet loss rates from 0.01% to 5%. The results confirmed that an appropriate slice partitioning scheme is essential to have a graceful degradation in received quality in the case of packet loss. While flexible macroblock ordering reduces the compression efficiency about 1 dB for our test material, reconstructed video quality is improved for loss rates above 0.25%. 相似文献
17.
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
18.
A new motion-compensated 3-D wavelet transform (MC-3DWT) video coding scheme is presented in thispaper. The new coding scheme has a good performance in average PSNR, compression ratio and visual quality of re-constructions compared with the existing 3-D wavelet transform (3DWT) coding methods and motion-compensated2-D wavelet transform (MC-WT) coding method. The new MC-3DWT coding scheme is suitable for very low bit-rate video coding. 相似文献
19.
A new motion-compensated 3-D wavelet transform (MC-3DWT) video coding scheme is presented in this paper. The new coding scheme
has a good performance in average PSNR, compression ratio and visual quality of reconstructions compared with the existing
3-D wavelet transform (3DWT) coding methods and motion-compensated 2-D wavelet transform (MC-WT) coding method. The new MC-3DWT
coding scheme is suitable for very low bit-rate video coding.
Project supported by the National Natural Science Foundation of China(69875009) 相似文献
20.
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