The loss and delay experienced by packets travelling along an Internet network path are mainly governed by the characteristics of a bottleneck link, such as available data rate and queue size. In this work, we propose a framework for rate-distortion optimized packet scheduling with adaptive rate control for media streaming over bandwidth-constrained bottleneck links. The framework computes optimal packet schedules while continuously adapting its instantaneous rate to the following three factors: the available data rate and the current queue size on the bottleneck link, and the congestion that packets transmitted under the schedules will create on the bottleneck link. Experimental results demonstrate that our framework does not lose in rate-distortion performance over rate-distortion optimized packet scheduling without strict rate control, while producing at the same time a much smoother instantaneous rate feeding the bottleneck queue. This in turn contributes to fairness to other flows sharing the bottleneck link and causes less variations in queue size, thereby avoiding queue overflow and unnecessarily long packet delays on the bottleneck link. 1.

We consider the problem of streaming packetized media over the Internet from a server through a base station to a wireless client, in a rate-distortion optimized way. For error control, we employ an incremental redundancy scheme, in which the server can incrementally transmit parity packets in response to negative acknowledgements fed back from the client. Computing the optimal transmission policy for the server involves estimation of the probability that a single packet will be communicated in error as a function of the expected redundancy (or cost) used to communicate the packet. In this paper, we show how to compute this error-cost function, and thereby optimize the server's transmission policy, in this scenario. 1

Multimedia applications involving the transmission of video over communication networks are rapidly increasing in popularity. Such applications can greatly benefit from adapting video coding parameters to network conditions as well as adapting network parameters to better support the application requirements. These two dimensions can both be viewed as allocating source and network resources to improve video quality. In this paper, we highlight recent advances in optimal resource allocation for real-time video communications over unreliable and resource constrained communication channels. More specifically, we focus on point-to-point coding and delivery schemes in which the sequences are encoded on the fly. We present a high-level framework for resource-distortion optimization. The framework can be used for jointly considering factors across network layers, including source coding, channel resource allocation, and error concealment. For example, resources can take the form of transmission energy in a wireless channel, and transmission cost in a DiffServ-based Internet channel. This framework can be used to optimally trade off resource consumption with end-to-end video quality in packet-based video transmission. After giving an overview of this framework, we review recent work in two areas—energy efficient wireless video transmission and resource allocation for Internet-based applications. Keywords—Cross-layer design, energy efficient, error resilience, distortion estimation, internet video, wireless video. I.

This paper addresses the problem of streaming packetized media over a lossy packet network through an intermediate proxy server to a client, in a rate-distortion optimized way. The proxy, located at the junction of the backbone network and the last hop to the client, coordinates the communication between the media server and the client using hybrid receiver/senderdriven streaming in a rate-distortion optimization framework. The framework enables the proxy to determine at every instant which packets, if any, it should either request from the media server or retransmit directly to the client, in order to meet a constraint on the average transmission rate while minimizing the average end-to-end distortion. Performance gains of up to 1.5 dB and up to 4 dB are observed over rate-distortion optimized senderdriven systems for the case when the last hop is wireline and wireless, respectively.

Abstract — We study hybrid error control for real-time video transmission. The study is carried out using a proposed integrated joint source-channel coding framework, which jointly considers error resilient source coding, channel coding, and error concealment, in order to achieve the best video quality. We focus on the performance comparison of several error correction scenarios, such as forward error correction (FEC), retransmission, and the combination of both. Simulation results show that either FEC or retransmission can be optimal depending on the packet loss rates and network round trip time. The proposed hybrid FEC/retransmission scheme outperforms both. I.

Abstract — In wireless video transmission, burst packet errors generally produce more catastrophic results than equal number of isolated errors. To minimize the playback distortion, it is crucial for the sender to know the packet errors at the receiver and then optimally schedule next transmissions. Unfortunately, in practice, feedback errors result in inaccurate observations of the receiving status. In this paper, we develop an optimal scheduling framework to minimize the expected distortion by first estimating the receiving status. Then, we jointly consider the source and channel characteristics and optimally choose the packets to transmit. The optimal transmission strategy is computed through a partially observable Markov decision process. The experimental results show that the proposed framework improves the average peak signal-to-noise ratio (PSNR) by 0.6-1.3dB upon using a traditional system without packets scheduling. Moreover, we show that the proposed method smoothes out the bursty distortion periods and results in less fluctuating PSNR values. I.

Internet transmission is characterized by variations in throughput, delay, and packet loss, which can severely affect the quality of multimedia presentations delivered over the network. Still, Internet video streaming has experienced phenomenal growth in the last few years, owing to the extensive research in video coding and transmission. In this paper, we review several recent advances for network-adaptive video streaming that, we believe, will benefit the design of video streaming systems in the future. Employed in different system components, these techniques have the common objective of providing efficient, robust, scalable and low-latency streaming video. They range from purely server or source encoder-based techniques, through transmission schemes that could be implemented either at the sender or at the receiver, to purely client-based techniques. We discuss each of them in detail, presenting also related work and experimental results. We end the paper with a summary of the reviewed techniques and a brief discussion of future research directions.

the Internet through an intermediate proxy server to a client, in a rate-distortion optimized way. The proxy employs a hybrid receiver/sender driven transmission scheme to communicate with both the media server and the client. Computing the optimal transmission policy for the proxy involves estimation of the probability that a single packet will be communicated to the client in error as a function of the expected redundancy (or cost) used to communicate the packet. In this paper, we show how to compute this error-cost function, and thereby optimize the proxy's transmission policy.

We consider an unconventional procedure for communicating to the server the receipt of media packets for Internet video streaming. Instead of separately acknowledging each media packet as it arrives, we periodically send to the server a single acknowledgment packet, denoted rich acknowledgment, that contains information about all media packets that have arrived at the client by the time the rich acknowledgment is sent. We investigate rate-distortion optimized sender-driven streaming that employs rich acknowledgments. Performance gains of up to 1.3 dB for streaming packetized video content are observed over rate-distortion optimized senderdriven systems that employ conventional acknowledgments.

We present techniques recently developed by our research group at Stanford University to improve the performance of existing algorithms for rate-distortion optimized video streaming. In rate-distortion optimized streaming, media packet transmissions are controlled in a way that gives an optimal tradeoff between the expected bit-rate that will be required for the transmissions and the expected media reconstruction distortion that will result. In one of the techniques that we present here, performance is improved by incorporating richer, more reliable feedback information. In another, multiple...