Error resilient video transmission over ATM networks

In the transmission process of a variable bit rate video signal over an ATM network, cells are inevitably exposed to delays and losses due to the statistical multiplexing used in these networks. These phenomena affect the quality of the video signal, and without adequate measures to control the propagation of impairments, the quality of service may fall below acceptable levels. We introduce a set of control mechanisms at different levels of the protocol architecture to support MPEG-2 based video communications systems using ATM networks as their underlying transmission mechanism. We argue that in order to be able to create video systems able to cope with cell losses encountered in computer communications systems, a structured set of protocol mechanisms is required. Our results show the effectiveness of the proposed set of mechanisms in improving the robustness of the video delivery system     

Error recovery for ATM transmission over wireless channels

The authors present a technique for efficient recovery from transmission errors to be used when transmitting ATM-like data packets in a wireless channel affected by bursty errors (jamming). Issues related to packet format error protection code structure and retransmission protocol are discussed and simulation results are shown that prove the effectiveness of the proposed approach     

User-aware object-based video transmission over the next generation Internet

In this paper, we present a new user-aware adaptive object-based video transmission approach to heterogeneous users over the next generation Internet. Firstly, we describe a new transport framework for complex multimedia applications over the next generation Internet, which provides differentiation functionality within one IP session as well as among different IP sessions. It includes application-aware intelligent resource control at the edge of the network, fast transcoding and signaling in the network. Secondly, we propose a new bitstream classification, prioritization and packetization scheme in which different types of data such as shape, motion and texture are reassembled, assigned to different priority classes, and packetized separately based on their priorities. Thirdly, we present a simple but effective mechanism of object-based dynamic rate control and adaptation by selectively dropping packets in conjunction with differentiated services (Diffserv) to minimize the end-to-end quality distortion. Finally, we perform the queuing analysis for our mechanism and explore how to extend our approach to the multicast case. Experimental results demonstrate effectiveness of our proposed approach.     

Error-resilient image and video transmission over the Internet using unequal error protection

This paper presents a new bit-plane-wise unequal error protection algorithm for progressive bitstreams transmitted over lossy networks. The proposed algorithm protects a compressed embedded bitstream generated by a 3-D SPIHT algorithm by assigning an unequal amount of forward error correction (FEC) to each bit-plane. The proposed algorithm reduces the amount of side information needed to send the size of each code to the decoder by limiting the number of quality levels to the number of bit-planes to be sent while providing a graceful degradation of picture quality as packet losses increase. We also apply our proposed algorithm to transmission of JPEG 2000 coded images over the Internet. To get additional error-resilience at high packet loss rates, we extend our algorithm to multiple-substream unequal error protection. Simulation results show that the proposed algorithm is simple, fast and robust in hostile network conditions and, therefore, can provide reasonable picture quality for video applications under varying network conditions.     

Adaptive video multicast over the Internet

The authors survey existing solutions to adaptive video multicast, providing a taxonomy of solutions according to several distinct features. They also review the principal techniques from both video coding and network transport perspectives. Finally, they discuss the evaluation methodologies and metrics for adaptive video multicast systems.     

不对称数字用户线上的多播视频传送

集中讨论了基于不对称数字用户线上多播视频业务的特性、体系结构及开发多播业务的几种关键技术，对目前用于传送的几种接入体系结构进行了分析比较。     

Potential for compressed video transmission over the GSM HSCSDservice

The author considers the evaluation of transmission of compressed video, for surveillance monitoring in the operation of light rail transport systems, over the emerging specification for the GSM high speed circuit switched data service (HSCSD), which can combine (dynamically) up to eight standard data channels as a single high speed channel     

Smoothing transcoded MPEG-1 video streams for Internet transmission

An efficient smoothing scheme for the real-time transmission of MPEG-1 transcoded video over 'best-effort' IP networks is presented. The scheme uses intelligent partitioning and multiplexing of the packetised bit stream. Bit-rate smoothing is achieved by partitioning packets according to their picture type (I, P or B). Subsequently, the partitioned packets are multiplexed in such a way that each packet from an anchor (I and P) picture is followed by two packets from B-pictures. The proposed scheme smooths the bit rate of the encoded video, making it more suitable for adaptive video streaming applications. In such applications, the transmission bit rate is varied so as to adapt to the available network bandwidth. The scheme reorganises the transmission order of the packets, spreading the less important packets from the B-pictures into the more important packets from the anchor pictures. This indicates a reduction in the likelihood of losing more important anchor packets as the bandwidth bottleneck increases, implying an improvement in the quality of transmitted video. A variety of simulations results are presented to demonstrate these points.     

Rate allocation for video transmission over lossy correlatednetworks

A novel rate allocation algorithm for video transmission over lossy networks subject to bursty packet losses is presented. A Gilbert-Elliot model is used at the encoder to drive the selection of coding parameters. Experimental results using the H.26L test model show a significant performance improvement with respect to the assumption of independent packet losses     

Scalable rate control for video transmission over UMTS

This paper proposes a mechanism for the congestion control for video transmission over Universal Mobile Telecommunications System (UMTS). Our scheme is applied when the mobile user experiences real time multimedia content and adopts the theory of a widely accepted rate control method in wired networks, namely equation‐based rate control. In this approach, the transmission rate of the multimedia data is determined as a function of the packet loss rate, the round trip time and the packet size and the server explicitly adjusts its sending rate as a function of these parameters. Through a number of simulations and experiments we validate the correctness and measure the performance and efficiency of the mechanism. A first level of evaluation is carried out using the ns‐2 simulator. A second level then validates the proposed mechanism in real world traffic scenarios by performing experiments in a commercial UMTS network. Copyright © 2006 John Wiley & Sons, Ltd.     

基于Internet的实时视频信号传输研究进展

随着Internet带宽和计算机处理能力的迅速提高,实时Internet视频传输在科研和工业领域引起了极大的研究兴趣。本文介绍了实时Internet视频传输的基本方法,针对Internet分组的丢失特性,讨论了具有差错复原能力的视频压缩与编码技术,详细介绍了Internet视频传输的信源／信道联方编码技术,并对今后的研究方向进行了概括的描述。     

Power management adaptation techniques for video transmission over TFRC

In this paper, we describe power management adaptation techniques for wireless video transmission using the TCP Friendly Rate Control (TFRC) protocol that take into account feedback about the received video quality and try to intelligently adapt transmitting power accordingly. The purpose of the mechanisms is to utilize TFRC feedback and thus achieve a beneficial balance between power consumption and the received video quality. There are two power adaptation mechanisms proposed, each one with its own advantages. They both offer significant improvements when used in terms of both power consumption and received video quality. We use simulation in order to compare and evaluate our approach. Copyright © 2011 John Wiley & Sons, Ltd.     

Rate control for robust video transmission over burst-errorwireless channels

We study the problem of rate control for transmission of video over burst-error wireless channels, i.e., channels such that errors tend to occur in clusters during fading periods. In particular we consider a scenario consisting of packet based transmission with automatic repeat request (ARQ) error control and a back channel. We start by showing how the delay constraints in real time video transmission can be translated into rate constraints at the encoder, where the applicable rate constraints at a given time depend on future channel rates. With the acknowledgments received through the back channel we have an estimate of the current channel state. This information, combined with an a priori model of the channel, allows us to statistically model the future channel rates. Thus the rate constraints at the encoder can be expressed in terms of the expected channel behavior. We can then formalize a rate distortion optimization problem, namely, that of assigning quantizers to each of the video blocks stored in the encoder buffer such that the quality of the received video is maximized. This requires that the rate constraints be included in the optimization, since violating a rate constraint is equivalent to violating a delay constraint and thus results in losing a video block. We formalize two possible approaches. The first one seeks to minimize the distortion for the expected rate constraints given the channel model and current observation. The second approach seeks to allocate bits so as to minimize the expected distortion for the given model. We use both dynamic programming and Lagrangian optimization approaches to solve these problems. Our simulation results demonstrate that both the video distortion at the decoder and packet loss rate can be significantly reduced when incorporating the channel information provided by the feedback channel and the a priori model into the rate control algorithm     

Error prevention and concealment for scalable video coding with dual-priority transmission

In this work, we present an efficient error resilient system against ATM cell loss using a hybrid error concealment and error propagation prevention (ECP) technique with dual-priority transmission scheme (DPTS). DPTS performs traffic policing to form dual-priority cells in ATM connections and manages to make most cell losses occur in a low priority layer. However, cell loss may still occur in the high priority layer if the bandwidth is not reserved enough for the usually variable bitrate video traffic. Therefore, the ECP technique can still be utilized to reduce the error damage and limit the impact of cell loss to the erroneous slices. Simulation results of two-layer MPEG-2 coding over DPTS in ATM networks demonstrate that ECP with feedback over DPTS can effectively isolate errors and reduce the damage to yield a satisfactory performance, even when the cell-loss rate is as high as 8%.     

Analysis of video transmission over lossy channels

A theoretical analysis of the overall mean squared error (MSE) in hybrid video coding is presented for the case of error prone transmission. Our model covers the complete transmission system including the rate-distortion performance of the video encoder, forward error correction, interleaving, and the effect of error concealment and interframe error propagation at the video decoder. The channel model used is a 2-state Markov model describing burst errors on the symbol level. Reed-Solomon codes are used for forward error correction. Extensive simulation results using an H.263 video codec are provided for verification. Using the model, the optimal tradeoff between INTRA and INTER coding as well as the optimal channel code rate can be determined for given channel parameters by minimizing the expected MSE at the decoder. The main focus of this paper is to show the accuracy of the derived analytical model and its applicability to the analysis and optimization of an entire video transmission system     

Rate adaptive video transmission over ad-hoc networks

A packet control mechanism via a cross-layer feedback to reduce bursts of packet drops for transmission of video over mobile multihop ad-hoc networks is presented. With this approach, the application layer would be capable of controlling the packet transmission flow in accordance with the multihop characteristics of the routing layer.     

Multirate video multicast over the Internet: an overview

Multirate multicast is an effective method for video distribution to a set of heterogeneous receivers. We present a comprehensive survey on multirate video multicast over the best effort Internet. We first review the key techniques in video encoding and network transport, and describe the representative approaches. We then study various trade-offs based on some important design issues and performance criteria, such as bandwidth economy, adaptation granularity, and coding complexity. Finally, we present some ongoing work and discuss possible avenues for future research.     

Transporting real-time video over the Internet: challenges andapproaches

Delivering real-time video over the Internet is an important component of many Internet multimedia applications. Transmission of real-time video has bandwidth, delay, and loss requirements. However the current Internet does not offer any quality of service (QoS) guarantees to video transmission over the Internet. In addition, the heterogeneity of the networks and end systems makes it difficult to multicast Internet video in an efficient and flexible way. Thus, designing protocols and mechanisms for Internet video transmission poses many challenges. In this paper, we take a holistic approach to these challenges and present solutions from both transport and compression perspectives. With the holistic approach, we design a framework for transporting real-time Internet video, which includes two components, namely, congestion control and error control. Specifically congestion control consists of rate control, rate-adaptive encoding, and rate shaping; error control consists of forward error correction (FEC), retransmission error resilience, and error concealment. For the design of each component in the framework, we classify approaches and summarize representative research work. We point out there exists a design space which can be explored by video application designers and suggest that the synergy of both transport and compression could provide good solutions     

Optimal multicast smoothing of streaming video over the Internet

A set of applications such as Internet video broadcasts, corporate telecasts, and distance learning require the simultaneous streaming of video to a large population of viewers across the Internet. The high bandwidth requirements and the multi-timescale burstiness of compressed video make it a challenging problem to provision network resources for streaming multimedia. For such applications to become affordable and ubiquitous, it is necessary to develop scalable techniques to efficiently stream video to a large number of disparate clients across a heterogeneous Internet. In this paper, we propose to multicast smoothed video over an application-level overlay network of proxies, and to differentially cache the video at the intermediate nodes (proxies) in the distribution tree, in order to reduce the network bandwidth requirements of video dissemination. We formulate the multicast smoothing problem as an optimization problem, and develop an algorithm for computing the set of transmission schedules for the tree that minimize the peak rate and rate variability, given buffer constraints at different nodes in the tree. We also develop an algorithm to compute the minimum buffer allocation in the entire tree, such that feasible transmission to all the clients is possible, when the tree has heterogeneous rate constraints. We show through trace-driven simulations that substantial benefits are possible from multicast smoothing and differential caching, and that these gains can be realized even with modest proxy caches.     

数字图像传输中的误差控制与掩蔽技术

讨论信道噪声和网络拥塞对数字图像传输造成的影响及其相应的解决方法。在不考虑网络自身因素的情况下，重点从编解码的角度出发探讨误码控制和掩蔽技术。