Abstract—We consider transmitting a source across a pair of independent, nonergodic channels with random states (e.g., slow-fading channels) so as to minimize the average distortion. The general problem is unsolved. Hence, we focus on comparing two commonly used source and channel encoding systems which correspond to exploiting diversity either at the physical layer through parallel channel coding or at the application layer through multiple description (MD) source coding. For on–off channel models, source coding diversity offers better performance. For channels with a continuous range of reception quality, we show the reverse is true. Specifically, we introduce a new figure of merit called the distortion exponent which measures how fast the average distortion decays with signal-to-noise ratio. For continuous-state models such as additive white Gaussian noise (AWGN) channels with multiplicative Rayleigh fading, optimal channel coding diversity at the physical layer is more efficient than source coding diversity at the application layer in that the former achieves a better distortion exponent. Finally, we consider a third decoding architecture: MD encoding with joint source–channel decoding. We show that this architecture achieves the same distortion exponent as systems with optimal channel coding diversity for continuous-state channels, and maintains the advantages of MD systems for on–off channels. Thus, the MD system with joint decoding achieves the best performance from among the three architectures considered, on both continuous-state and on–off channels. Index Terms—Application layer diversity, diversity, joint source–channel coding, multiple description coding, parallel channels. I.

Multirate multicast is an effective method for video distribution to a set of heterogeneous receivers. In this article 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.

This paper examines the effectiveness of combining multiple description coding (MDC) and multiple path transport (MPT) for video and image transmission in a multihop mobile radio network. The video and image information is encoded nonhierarchically into multiple descriptions with the following objectives. The received picture quality should be acceptable, even if only one description is received and every additional received description contributes to enhanced picture quality. Typical applications will need a higher bandwidth/higher reliability connection than that provided by a single link in current mobile networks. For supporting these applications, a mobile node may need to set up and use multiple paths to the desired destination, either simply because of the lack of raw bandwidth on a single channel or because of its poor error characteristics, which reduce its effective throughput. In the context of this work, the principal reasons for considering such an architecture are providing high bandwidth and more robust end-to-end connections. We describe a protocol architecture that addresses this need and, with the help of simulations, we demonstrate the feasibility of this system and compare the performance of the MDC-MPT scheme to a system using layered coding and asymmetrical paths for the base and enhancement layers.

This paper addresses the problem of video coding in a joint source-channel setting. In particular, we propose a video encoding algorithm that prevents the indefinite propagation of errors in predictively encoded video---a problem that has received considerable attention over the last decade. This is accomplished by periodically transmitting a small amount of additional information, termed coset information, to the decoder, as opposed to the popular approach of periodic insertion of intra-coded frames. Perhaps surprisingly, the coset information is capable of correcting for errors, without the encoder having a precise knowledge of the lost packets that resulted in the errors. In the context of real-time transmission, the proposed approach entails a minimal loss in performance over conventional encoding in the absence of channel losses, while simultaneously allowing error recovery in the event of channel losses. We demonstrate the efficacy of the proposed approach through experimental evaluation. In particular, the performance of the proposed framework is 3--4 dB superior to the conventional approach of periodic insertion of intra-coded frames, and 1.5--2 dB away from an ideal system, with infinite decoding delay, operating at Shannon capacity.

Typical video applications may need a higher bandwidth and/or higher reliability connection than that provided by a single link in current or emerging wireless networks. We propose to employ path diversity to provide higher bandwidth and more robust end-to-end connections than that affordable by a single path. Under this transport environment, two viable strategies for video coding are multiple description coding (MDC) and layered coding (LC). MDC is more effective when the underlying application has a very stringent delay constraint and the round trip time on each path is relatively long. LC can be a good alternative when limited retransmission of the base layer is acceptable and when it is feasible to apply unequal error protection over different paths. This paper describes the general issues involved in integrating MDC/LC with multiple path transport, and compares the performances of MDC and LC, under different path conditions.

We investigate how to transmit video with low latency when multiple burst-loss channels are available. We present a transmission strategy based on feedback for multiple description video. The strategy determines dynamically on which channels video frames and probe packets should be sent. Its goal is to find reliable paths and send independent descriptions on different channels. A multiple description with restart coding scheme is used and ensures a high level of error concealment. When errors are detected and a description is corrupted, the scheme selects a reliable ref- erence frame to restart the stream. We also show that the rate of probe packets can be rate-distortion optimized. Experiments demonstrate significant gains over other schemes such as video redundancy coding.

In this paper, we address the problem of real-time video communication over wireless ad hoc networks. For the unicast case, we propose a robust multipath source routing protocol for both interactive and video on-demand applications. Simulations show that our proposed scheme enhances the quality of video applications as compared to existing protocols. For the multicast case, we propose multiple tree multicast streaming as a way to provide robustness for video multicast applications. Specifically, we propose a distributed double disjoint tree multicast routing protocol called Serial MDTMR, and characterize its performance via simulations. We show that Serial MDTMR achieves reasonable tree connectivity while maintaining disjointness of two trees, and that it outperforms single tree multicast communication. 1.

In this paper we address the problem of video transmission over unreliable networks using Multiple Description (MD) coding approach. Recent literature on MD techniques has shown the success of using motion compensation prediction scheme. Even though these MD systems have proved to be robust to error environment, they are forced to use only two descriptions. For this reason this paper proposes two architectures of MD video coders. The first, called DC-MDVC, is based on the classical MD video codec architecture and the principle contribution is the use of a new MD algorithm based on a spatial domain polyphase down-sampling technique. The second architecture, called IF-MDVC, proposes multi-level scalability generating a flexible number of descriptions. The results of both architectures are interesting and the second architecture, the subject of the current research, appears to perform impressively. 1.

Abstract- Multihypothesis motion-compensated prediction (MHMCP) approach has shown significant gain in terms of coding efficiency both in theory and practice. However, the fact that it also enhances the error resilience of a codec has not been fully realized. This paper analyzes the error resilience gain of MHMCP. Models for the decoder distortion induced by transmission errors and the ratedistortion function of the encoder in a codec using MHMCP are presented and their accuracy is validated by simulation studies. Using these models, we show how to design the multihypothesis predictor to jointly consider the coding gain and the error resilience gain for given channel error characteristics.

Abstract—Efficient peer-to-peer (P2P) video streaming is a challenging task due to time-varying nature of both the number of available peers and network/channel conditions. This paper proposes a novel adaptive P2P video streaming system, which features: i) a new flexible multiple-description coding (F-MDC) framework, such that the number of base and enhancement descriptions, and the rate and redundancy level of each description can be adapted on the fly (by only post-processing of the encoded bitstream), and ii) a new adaptive TCP-friendly rate-controlled (TFRC), on-demand, many-to-one P2P video streaming solution based on the proposed F-MDC framework. We extend the highly scalable video coder [17], [18] to MDC within the proposed F-MDC framework. Optimization of the design parameters of the proposed F-MDC method is discussed within the context of the proposed adaptive P2P streaming solution, where the number and quality of available streaming peers/paths are a priori unknown and vary in time. Experimental results, by means of NS-2 network simulation of a P2P video streaming system, show that adaptation of the number, type of descriptions and the rate and redundancy level of each description according to network conditions yields significantly superior performance when compared to other scalable MDC schemes using a fixed number of descriptions/layers with fixed rate and redundancy level. Index Terms—Adaptive P2P streaming, multiple description coding, rate-distortion optimization, scalable video coding, TCP-friendly rate-controlled (TFRC). I.