18455016
Channel-adaptive video streaming using packet path diversity and rate-distortion optimized reference picture selection
In this paper, we present error-resilient Internet video transmission using path diversity and rate-distortion optimized reference picture selection. Under this scheme, the optimal packet dependency is determined adapting to channel characteristics and video content, to achieve a better trade-off between coding efficiency and forming independent streams to increase error resilience. Packets are sent over the selected path that minimizes the distortion, while taking advantage of path diversity. Experiments demonstrate that the proposed scheme provides significant gains over video redundancy coding and the NACK mode of conventional reference picture selection.
7289490
Low-latency video transmission over lossy packet networks using rate-distortion optimized reference picture selection
Today's Internet video streaming systems employ buffering and multiple retransmissions to guarantee the correct reception of each packet, which leads to high latency in media delivery. In this work, a novel scheme of dynamic management of the dependency across packets is proposed using optimal reference picture selection at the frame level that adapts to the channel. The optimal selection of the reference picture is achieved with a rate-distortion framework, which minimizes the expected end-to-end distortion given a rate constraint. The expected distortion is calculated based on an accurate binary tree modeling with the effects of channel loss and error concealment taken into account. Experiments demonstrate that the proposed :scheme provides significant performance gains over a simple INTRA-insertion scheme. The increased error-resilience eliminates the need of retransmission, which makes it possible to reduce the latency from 10-15 seconds to a few hundred milliseconds, with similar video quality maintained.
6443463
Prescient R-D optimized packet dependency management for low-latency video streaming
An improved, prescient, scheme to deliver preencoded video streams at very low latency is presented. We dynamically manage the prediction dependency for a group of packets using a rate-distortion (R-D) optimization framework that adapts to the channel, so that the expected end-to-end distortion is minimized under a given rate constraint. In our system, the R-D characteristics of each prediction mode are precomputed at compression time and stored in an R-D preamble along with the multiple compressed versions of the stream. The distortion in the preamble is estimated using an accurate loss-distortion model, and the optimal prediction modes are computed with an iterative descent algorithm. Complexity is reduced at streaming time by using the preamble to compute the optimal modes instead of actually compressing the video. Experiments demonstrate that the proposed prescient scheme provides significant performance gains over simple intra-insertion, and consistent bitrate savings compared to the greedy scheme.
5685846
Advances in channel-adaptive video streaming
Despite the well-known challenges of variations in throughput, delay, and packet loss over the Internet, video streaming has experienced phenomenal growth, owing to the extensive research in video coding and transmission. In this paper, we review several recent advances for channel-adaptive video streaming that, we believe, will benefit the design of video streaming systems in the future. Employed in different components of the system, these techniques have the common objective of providing efficient, robust, scalable, and low-latency streaming video. Firstly, by allowing the client to control the rate at which it consumes data, adaptive media playout can be used to reduce receiver buffering and therefore average latency, and provide limited rate scalability. Secondly, rate-distortion optimized packet scheduling, a transport technique, provides a flexible framework to determine the best packet to send, given the channel behaviors, the packets' deadlines, their transmission histories, the distortion reduction associated with sending each packet, and the interpacket dependencies. Thirdly, at the source encoder, channel-adaptive packet-dependency control can greatly improve the error resilience of streaming video and reduce latency. Finally, we address the specific additional challenges for wireless video streaming. We consider three architectures for wireless video and discuss the utility of the reviewed techniques for each architecture. Copyright © 2002 John Wiley & Sons, Ltd.
399310
Real-time voice communication over the internet using packet path diversity
The quality of real-time voice communication over best-effort networks is mainly determined by the delay and loss characteristics observed along the network path. Excessive playout buffering at the receiver is prohibitive and significantly delayed packets have to be discarded and considered as late loss. We propose to improve the tradeoff among delay, late loss rate, and speech quality using multi-stream transmission of real-time voice over the Internet, where multiple redundant descriptions of the voice stream are sent over independent network paths. Scheduling the playout of the received voice packets is based on a novel multi-stream adaptive playout scheduling technique that uses a Lagrangian cost function to trade delay versus loss. Experiments over the Internet suggest largely uncorrelated packet erasure and delay jitter characteristics for different network paths which leads to a noticeable path diversity gain. We observe significant reductions in mean end-to-end latency and loss rates as well as improved speech quality when compared to FEC protected single-path transmission at the same data rate. In addition to our Internet measurements, we analyze the performance of the proposed multi-path voice communication scheme using the ns network simulator for different network topologies, including shared network links.
34209487
Advances in channel-adaptive video streaming
We review recent advances in channel-adaptive video streaming. Adaptive media playout at the client can be used to reduce receiver buffering and therefore average latency, and provide a limited rate scalability. Rate-distortion optimized packet scheduling determines the best packet to send given the distortion reduction associated with sending that packet, interpacket dependencies, and the success of past transmissions. Channel-adaptive packet dependency control can greatly improve the error-robustness of streaming video and reduce or eliminate the need for packet retransmissions. Finally we consider three architectures for wireless video streaming and discuss the utility of the discussed techniques for each architecture.
41985683
Constraint Satisfaction In "Conscious" Software Agents--A Practical Application
ABSTRACT The U.S. Navy has been trying for many years to automate its personnel assignment process. Periodic assignment of personnel to new jobs is mandatory according to Navy policy. Though various software systems are used regularly, the process is mainly done manually and sequentially by Navy personnel called detailers. This paper is a case study in applying cognitive theories implemented via new AI techniques to produce flexible adaptive human-like software. In it we present a sketch of an intelligent distribution agent that aims to largely automate the detailer's tasks. In particular, we look inside its constraint satisfaction, which is mainly responsible for satisfying the requirements of the Navy's policies, the command's needs, and the sailor's preferences in order to achieve “satisfactory” job assignments, according to ever-evolving Navy standards.
1136997
Cooperative Relay Broadcast Channels
The capacity regions are investigated for two relay broadcast channels (RBCs), where relay links are incorporated into two-user broadcast channels to support user cooperation. In the first channel, the partially cooperative RBC, only one user in the system acts as a relay. An achievable rate region is derived based on the relay using the decode-and-forward scheme. An outer bound on the capacity region is derived and is shown to be tighter than the cut-set bound. For the special case where the partially cooperative RBC is degraded, the achievable rate region is shown to be the capacity region. Two Gaussian cases of the partially cooperative RBC are studied. For the system where the additive white Gaussian noise (AWGN) term at one receiver is a degraded version of the other, which we refer to as the D-AWGN partially cooperative RBC, the capacity region is established. For the system where the AWGN term at one receiver is independent of the other, which we refer to as the AWGN partially cooperative RBC, inner and outer bounds on the capacity region are derived and are shown to be close. Furthermore, it is shown that feedback does not increase the capacity region for the degraded partially cooperative RBC, but that it improves the capacity region for the nondegraded version. In particular, feedback improves the capacity region for the AWGN partially cooperative RBC. In the second channel model being studied in the paper, the fully cooperative RBC, both users can act as relay nodes. All the results for the partially cooperative RBC are correspondingly generalized to the fully cooperative RBC. In particular, capacity regions are established for the degraded and D-AWGN fully cooperative RBCs. The capacity region is also established for the fully cooperative RBC with feedback. It is further shown that the AWGN fully cooperative RBC has a larger achievable rate region than its partially cooperative counterpart. The results illustrate that relaying and user cooperation are powerful techniques for improving the capacity of broadcast channels
26412340
Finding a Maximum Matching in a Circular-Arc Graph
We present an O(n log n) algorithm for finding a maximum matching in a circular-arc graph. The best known algorithm for the same problem in general graphs takes O(√|V||E|) time.
38500613
On the Feedback Vertex Set Problem in Permutation Graphs
Abstract Brandstadt and Kratsch (1987) presented an O( n 6 ) time algorithm for the minimum weight feedback vertex set problem in a permutation graph of n vertices and m edges. This result was recently improved to O( n.m.m ) by Brandstat (1993), where m is the number of edges in the complement of G . In this paper, we employ a different dynamic programming scheme to reduce the time complexity to O( nm ) for this problem in permutation graphs.
10881008
Steiner Set and Connected Domination in Trapezoid Graphs
Abstract Trapezoid graphs are extensions of interval graphs and permutation graphs. This paper presents an O (¦V¦) time algorithm for finding a minimum cardinality Steiner set and an O (¦E¦ + ¦V¦) time algorithm for finding a minimum cardinality connected dominating set in a trapezoid graph G = ( V , E ), given the trapezoid diagram.