The burstiness of a video source can be characterized by its burstiness curve. The burstiness curve is useful in the optimal allocation of resources to satisfy a desired quality of service for the video stream in a packet network. In this paper, we present deterministic algorithms for exact computation of the burstiness curve of a video source, for both elementary video streams and MPEG-2 Transport Streams. The algorithms exploit the piecewise linearity of the burstiness curve and compute only the points at which the slope of the burstiness curve changes. We also present approximate versions of these algorithms, which save computational effort by considering only a small number of candidate points at which the slope of the burstiness curve may change. The approximate algorithm was able to compute the burstiness curve of a 2-h long elementary video stream in approximately 10 s, as compared to over 6 h for the exact algorithm, with virtually no loss of accuracy in the computation. The efficiency of the proposed algorithms makes them suitable for quality-of-service (QoS) provisioning not only in off-line environments such as in video-on-demand (VoD) servers, but also in real-time applications such as in live TV distribution systems.

One of the challenges the service providers currently face is the ability to introduce a variety of services at a minimal cost and impact to their customers. These services often become personalized as more and more content becomes available. The natural progression to the service/content explosion is a seamless user interface that remains consistent across the various services and devices. The Essistant architecture attempts to provide personalized services to the end users through a seamless multi-modal user interface and a systematization of the backend services. This paper describes the overall architecture of the Essistant project. The associated video demonstrates the functionality of Essistant for a set of services that have been implemented in a lab environment. The services include video-on-demand using an automated price broker, broadcast video over IP multicast, personalized news, and horoscope, and interaction with the physical space by acting as a proxy to a robot.

The loss curve of a video source characterizes the loss rate of the video stream generated by the source as a function of the allocated buffer size for a given transmission rate. The loss curve is useful in the optimal allocation of resources when the video stream is transmitted over a packet network, so that the desired tradeoff can be reached among the loss rate, bandwidth and the buffer space to be allocated in the network. We present an algorithm for computation of the entire loss curve of an elementary video stream. In contrast to earlier algorithms which employ statistical approaches, our algorithm is deterministic and computes the exact loss curve of the video stream. The algorithm exploits the piecewise linearity of the loss curve and computes only the points at which the slope of the loss curve changes. We also present an extension of the algorithm to MPEG-2 transport streams. The efficiency of the algorithm is demonstrated by results from several example video streams. For example, the algorithm was able to compute the entire loss curve of a 2-h elementary video stream in approximately 11 s on a Sun Ultra-2 workstation.

This paper addresses the clock recovery problem while transporting MPEG-2 systems layer streams over packet-switched networks. The packet delay variation (jitter) introduced by the network affects the stability and thus the quality of the recovered clock. A decoder design methodology is described in which a jitter estimator that performs restamping on all the incoming packets containing clock values is used in conjunction with a standard phase-locked loop (PLL). A simple implementation of this methodology is described, where a new heuristic has been added to the standard PLL to eliminate the effects of the jitter. The methodology is evaluated by both analysis and extensive simulation experiments in a multi-hop ATM network using constant bit-rate MPEG-2 transport streams produced by hardware encoders with varying levels of cross traffic. The results show that the restamping approach outperforms standard dejittering methods, especially under heavy load conditions.

We propose and analyze several strategies for performing timestamping of an MPEG-2 Transport Stream transmitted over a packet-switched network using the PCR-unaware encapsulation scheme, and analyze their effect on the quality of the recovered clock at the MPEG-2 Systems decoder. When the timestamping scheme is based on a timer with a fixed period, the PCR values in the packet stream may switch polarity deterministically, at a frequency determined by the timer period and the transport rate of the MPEG signal. This, in turn, can degrade the duality of the recovered clock at the receiver beyond acceptable limits. We consider three timestamping schemes for solving this problem: (1) selecting a deterministic timer period to avoid the phase difference in PCR values altogether, (2) fine-tuning the deterministic timer period to maximize the frequency of PCR polarity changes, and (3) selecting the timer period randomly to eliminate the deterministic PCR polarity changes. For the case of deterministic timer period, we derive the frequency of the PCR polarity changes as a function of the timer period and the transport rate, and use it to find ranges of the timer period for acceptable quality of the recovered clock. We also analyze a random timestamping procedure based on a random telegraph process and obtain lower bounds on the rate of PCR polarity changes such that the recovered clock does not violate the PAL/NTSC clock specifications. The analytical results are verified by simulations with both synthetic and actual MPEG-2 Transport Streams sent to a simulation model of an MPEG-2 Systems decoder.