Jeonghun Noh

Rate-distortion optimized video peer-to-peer multicast streaming

We study peer-to-peer multicast streaming, where a source distributes real-time video to a large population of hosts by making use of their forwarding capacity rather than relying on dedicated media servers. Hosts which may disconnect at any time, therefore a robust control protocol is needed to maintain connectivity among peers. This work presents a new peer-to-peer multicast protocol and analyzes the gains that video coding and prioritized packet scheduling at the application layer can bring to the overall streaming performance. A rate-distortion model which predicts end-to-end video quality in throughput limited environments is presented and used to determine the over-provisioning necessary to avoid self-inflicted congestion. The video stream transmitted by the source contains H.264 SP and SI frames, which are used to adaptively stop error propagation due to packet loss. Distortion-optimized retransmission requests are issued by receiving hosts to recover the most important missing packets while limiting the induced congestion. Experiments for several hundred hosts simulated in NS-2 illustrate the benefits of our system. We achieve typical end-to-end delays of 1 sec, and a stable video quality with less than 2.5% of frames lost to playout interruptions.

Content-Aware P2P Video Streaming with Low Latency

This paper describes the Stanford P2P multicast (SPPM) streaming system that employs an overlay architecture specifically designed for low delay video applications. In order to provide interactivity to the user, this system has to keep the end-to-end delay as small as possible while guaranteeing a high video quality. A set of complimentary multicast trees is maintained to efficiently relay video traffic and a congestion-distortion optimized (CoDiO) scheduler prioritizes more important video packets. Local retransmission is employed to mitigate packet loss. Real-time experiments performed on the Planet-Lab show the effectiveness of the system and the benefits of a content-aware scheduler in case of congestion or node failures.

Low Latency Video Streaming Over Peer-To-Peer Networks

We study peer-to-peer multicast streaming, where a source distributes real-time video to a large population of hosts by making use of their forwarding capacity rather than relying on dedicated media servers. We present a distributed streaming protocol which builds and maintains multiple multicast trees. The protocol is combined with an adaptive scheduling algorithm which ensures packets destined to a large number of peers, or particularly important to decode the video, are sent in priority. Experiments carried out over a simulated network of up to 3000 peers illustrate the performance of the protocol. For low latency video streaming, the prioritization algorithm offers performance gains, especially for large audiences and low latencies

Peer-to-peer multicast live video streaming with interactive virtual pan/tilt/zoom functionality

Video streaming with virtual pan/tilt/zoom functionality allows the viewer to watch arbitrary regions of a high-spatial-resolution scene. In our proposed system, the user controls his region-of-interest (ROI) interactively during the streaming session. The relevant portion of the scene is rendered on his screen immediately. An additional thumbnail overview aids his navigation. We design a peer-to-peer (P2P) multicast live video streaming system to provide the control of interactive region-of-interest (IROI) to large populations of viewers while exploiting the overlap of ROIs for efficient and scalable delivery. Our P2P overlay is altered on-the-fly in a distributed manner with the changing ROIs of the peers. The main challenges for such a system are posed by the stringent latency constraint, the churn in the ROIs of peers and the limited bandwidth at the server hosting the IROI video session. Experimental results with a network simulator indicate that the delivered quality is close to that of an alternative traditional unicast client-server delivery mechanism yet requiring less uplink capacity at the server.

Congestion-Distortion Optimized Peer-to-Peer Video Streaming

In live peer-to-peer streaming, a video stream is transmitted to a large population of viewers, through the use of the uplink bandwidth of participating peers. This approach overcomes the cost of large-scale deployment of such services. An essential problem of this type of system is to limit the incurred congestion. In particular, overwhelming the uplink of some peers would create a large increase in the latency of the system and make this application less compelling. In this work we focus on limiting the congestion in a peer-to-peer network where multiple multicast trees are used to distribute video to a large set of receivers. We present the idea of congestion-distortion optimized streaming which aims at maximizing decoded video quality while limiting network congestion. We describe how this type of media scheduling maintains high video quality even for low latencies, and extend its usage to the peer-to-peer scenario. Experiments over a simulated network of 300 peers illustrate the benefits of the suggested approach.

Stanford Peer-to-Peer Multicast (SPPM) - Overview and recent extensions

We review the Stanford Peer-to-Peer Multicast (SPPM) protocol for live video streaming and report recent extensions. SPPM has been designed for low latency and robust transmission of live media by organizing peers within multiple complementary trees. The recent extensions to live streaming are time-shifted streaming, interactive region-of-interest (IRoI) streaming, and streaming to mobile devices. With time-shifting, users can choose an arbitrary beginning point for watching a stream, whereas IRoI streaming allows users to select an arbitrary region to watch within a high-spatial-resolution scene. We extend the live streaming to mobile devices by addressing challenges due to heterogeneous displays, connection speeds, and decoding capabilities.

P2TSS: Time-shifted and live streaming of video in peer-to-peer systems

In this study, we propose P2TSS, a novel peer-to-peer streaming system which can provide live and time-shifted streams. To achieve time-shifting in a peer-to-peer system, video contents are segmented and spread out in the local caches of participating peers. We present two lightweight distributed cache algorithms: initial play-out position caching and live stream position caching. These algorithms enable peers to locally decide which video blocks to cache for sharing with other peers. We provide an extensive analysis of these cache algorithms to derive the availability of video blocks and the average number of available peers for a certain video block at a given time. Our simulations show that P2TSS achieves low server stress by fully utilizing peerspsila local cache and uplink bandwidth.

Optimal server bandwidth allocation for streaming multiple streams via P2P multicast

We consider the general scenario where content hosted by the server comprises streams and each peer can subscribe one or more streams. Multiple multicast trees are built to deliver the streams to respective peers while exploiting the overlap of their interests for efficient and scalable delivery. We propose an optimization framework for allocating server bandwidth to minimize distortion across the peer population. We apply the framework to a novel application, peer-to-peer (P2P) multicast live video streaming with virtual pan/tilt/zoom functionality. In this application, each user can watch arbitrary regions of a high-spatial-resolution scene yet the system exploits overlapping interests by building multicast trees. Experimental results indicate that optimal server bandwidth allocation enhances the delivered quality across the peer population.

Reducing end-to-end transmission delay in P2P streaming systems using multiple trees with moderate outdegree

We propose an overlay consisting of multiple trees with moderate outdegree to reduce end-to-end transmission delays in P2P media streaming systems. In real-time media streaming, lower end-to-end delays lead to less waiting time before playback and hence improve interactivity. A theoretical analysis of degree-bounded trees reveals that an optimal number of multiple trees can be chosen by considering the trade-off between the total propagation delay and the queueing delay experienced at intermediate peers. A distributed protocol is presented that allows peers to build multiple degree-bounded trees. From extensive packet-level simulations, we observe that the worst end-to-end transmission delay is minimized when the peerpsilas outdegree, or fan-out, is between 4 and 6 for realistic simulation parameters. This matches well with the predictions from our analysis.

Time-Shifted Streaming in a Peer-to-Peer Video Multicast System

We propose a peer-to-peer (P2P) streaming system that allows users to individually pause and resume a live video stream as well as to view video that was streamed before the particular user joined the session. Such time-shifted streaming can be provided by caching a portion of the video stream at each peer and serving it asynchronously. We analyze the availability of video contents in the P2P overlay using a Poisson model of peer arrival. We also discuss fast prefetching, which reduces video disruption due to peer churn and also allows peers to disseminate content more quickly, thus reducing server bandwidth requirement. We extend the Stanford Peer-to-Peer Multicast (SPPM) protocol to support time-shifted streaming. The overlay is constructed by selecting parent nodes that are expected to most effectively support fast prefetching. Extensive network experiments show that fast prefetching effectively supports time-shifted streaming with reduced server load.