Yi Cui

The emergence of cloud encoding services facilitates many content owners, such as the online video vendors, to transcode their digital videos without infrastructure setup. Such service provider charges the customers only based on their resource consumption. For both the service provider and customers, lowering the resource consumption while maintaining the quality is valuable and desirable. Thus, to choose a cost-effective encoding parameter, configuration is essential and challenging due to… Show more

The emergence of cloud encoding services facilitates many content owners, such as the online video vendors, to transcode their digital videos without infrastructure setup. Such service provider charges the customers only based on their resource consumption. For both the service provider and customers, lowering the resource consumption while maintaining the quality is valuable and desirable. Thus, to choose a cost-effective encoding parameter, configuration is essential and challenging due to the tradeoff between bitrate, encoding speed, and resulting quality. In this paper, we explore the feasibility of an automatic parameter-tuning framework, based on which the above objective can be achieved. We introduce a simple service model, which combines the bitrate and encoding speed into a single value: encoding cost. Then, we conduct an empirical study to examine the relationship between the encoding cost and various parameter settings. Our experiment is based on the one-pass Constant Rate Factor method in x264, which can achieve relatively stable perceptive quality, and we vary each parameter we choose to observe how the encoding cost changes. The experiment results show that the tested parameters can be independently tuned to minimize the encoding cost, which makes the automatic parameter-tuning framework feasible and promising for optimizing the cost on video encoding cloud. Show less

Peer-to-peer (P2P) is a powerful platform for a variety of multimedia streaming applications over the Internet such as video-on-demand, video conferencing, live broadcasting, etc. A P2P system is extremely cost-effective since it utilizes the resources (CPU cycles, storage space, and uplink bandwidth) of peer machines.The decentralized and shared bandwidth nature of a P2P network, therefore, makes it an effective choice for implementing video conferencing applications. In this work, Vanets is… Show more

Peer-to-peer (P2P) is a powerful platform for a variety of multimedia streaming applications over the Internet such as video-on-demand, video conferencing, live broadcasting, etc. A P2P system is extremely cost-effective since it utilizes the resources (CPU cycles, storage space, and uplink bandwidth) of peer machines.The decentralized and shared bandwidth nature of a P2P network, therefore, makes it an effective choice for implementing video conferencing applications. In this work, Vanets is presented , a P2P based video conferencing system that takes advantage of transcoding to optimally allocate streaming rates for all participating peers. The solution presented in this paper distinguishes between active and passive participants and enhances the video quality of the active participant. Show less

Recent theoretical and simulation-based studies have confirmed the tremendous benefit of peer-to-peer (P2P)communication at reducing the cost of running a VoD service.To date, very limited effort has been paid to validate the concept of peer-assisted VoD service, especially in terms of system implementation and service deployment. In this paper, we present the case study of a peer-assisted video-on-demand (VoD) system. We designed and developed Bit-Tube, a BitTorrent-compliant VoD system. By… Show more

Recent theoretical and simulation-based studies have confirmed the tremendous benefit of peer-to-peer (P2P)communication at reducing the cost of running a VoD service.To date, very limited effort has been paid to validate the concept of peer-assisted VoD service, especially in terms of system implementation and service deployment. In this paper, we present the case study of a peer-assisted video-on-demand (VoD) system. We designed and developed Bit-Tube, a BitTorrent-compliant VoD system. By combining client/server and P2P downloading, it supports seamless transition across the spectrum from pure client-server mode to BitTorrent mode. Within this framework, we experiment with a series of piece picking policies to enhance BitTubepsilas support to video streaming and promote locality-aware P2P downloading. We evaluate our system over PlanetLab,which hosts the user-side component of the BitTube system and emulates the global-scale user requests to the VoD service. Show less

We have developed PeerStreaming, an on-demand peer-to-peer (P2P) media streaming system. The behavior of a PeerStreaming client is very much like an ordinary media player: it streams and plays whatever media the user desires, starting at whatever point he/she
desires. Under the hood, however, the media is delivered
frommultiple peers to the client. The serving peers can be the media server, but more commonly they are the clients that have received the media in a previous streaming… Show more

We have developed PeerStreaming, an on-demand peer-to-peer (P2P) media streaming system. The behavior of a PeerStreaming client is very much like an ordinary media player: it streams and plays whatever media the user desires, starting at whatever point he/she
desires. Under the hood, however, the media is delivered
frommultiple peers to the client. The serving peers can be the media server, but more commonly they are the clients that have received the media in a previous streaming session. Leveraging the network and storage resources of the P2P network and retrieving amajor part of the media from nearby peers, PeerStreaming greatly improves streaming media quality, reduces server load, and eases traffic on the network.We describe the design and implementation of the PeerStreaming system in this
paper, with a focus on a number of key components. They include: (1) peer discovery and content location, (2) scalable coded and randomly accessible media format, (3) receiver-driven streaming, (4) digital rightsmanagement, and (5) architecture for the media rendering, caching and serving system. Show less

In this paper, we examine the problem of large-volume data dissemination via overlay networks. A natural way to maximize the throughput of an overlay multicast session is to split the traffic and feed them into multiple trees. While in single-tree solutions, bandwidth of leaf nodes may remain largely under-utilized, multi-tree solutions increase the chances for a node to contribute its bandwidth by being a relaying node in at least one of the trees. We study the following problems: (1) What is… Show more

In this paper, we examine the problem of large-volume data dissemination via overlay networks. A natural way to maximize the throughput of an overlay multicast session is to split the traffic and feed them into multiple trees. While in single-tree solutions, bandwidth of leaf nodes may remain largely under-utilized, multi-tree solutions increase the chances for a node to contribute its bandwidth by being a relaying node in at least one of the trees. We study the following problems: (1) What is the maximum capacity multi-tree solutions can exploit from overlay networks? (2) When multiple sessions compete within the same network, what is the relationship of two contradictory goals: achieving fairness and maximizing overall throughput? (3) What is the impact of IP routing in achieving at constraining the optimal performance of overlay multicast? We extend the multicommodity flow model to the case of overlay data dissemination, where each commodity is associated with an overlay session, rather than the traditional source-destination pair. We first prove that the problem is solvable in polynomial time, then propose an #-approximation algorithm, assuming that each commodity can be split in arbitrary ways. The solution to this problem establishes the theoretical upper bound of overall throughput that any multi-tree solution could reach. We then study the same problem with the restriction that each commodity can only be split and fed into a limited number of trees. A randomized rounding algorithm and an online tree-construction algorithm are presented. All these algorithms are evaluated by extensive simulations. Show less

Building and dynamically configuring component-based systems is an important topic in distributed systems and ubiquitous computing. However, the systematic and automatic configuration management remains a challenging problem for the following reasons: (1) QoS-enforced service delivery demands to maximize the system performance out of the best configuration, (2) dynamically varied resource availability in the distributed environment makes it desirable to achieve the optimized system resource… Show more

Building and dynamically configuring component-based systems is an important topic in distributed systems and ubiquitous computing. However, the systematic and automatic configuration management remains a challenging problem for the following reasons: (1) QoS-enforced service delivery demands to maximize the system performance out of the best configuration, (2) dynamically varied resource availability in the distributed environment makes it desirable to achieve the optimized system resource consumption. We present a graph-based dependency management model to address the above problems. Our model integrates the management of inter-component functional dependency, including consistency checking and automatic system configuration, as well as QoS-aware resource dependency management. Based on the model, we present a pruning-based configuration selection algorithm, which is able to consistently optimize the system resource consumption, while preserving the QoS level in a heteregeneous environment. Our initial simulation results prove the soundness of our model and algorithm Show less

In this paper we propose a quantitative model to study user satisfaction level in online video streaming, which features great variety across video access sessions under the impact of network conditions and user-specific factors. By applying survival analysis to video session duration ratio, which in our study is regarded to be a measure of user satisfaction level, we find user satisfaction is not only related to network QoS factors, such as buffer time and buffer count, but also susceptible to… Show more

In this paper we propose a quantitative model to study user satisfaction level in online video streaming, which features great variety across video access sessions under the impact of network conditions and user-specific factors. By applying survival analysis to video session duration ratio, which in our study is regarded to be a measure of user satisfaction level, we find user satisfaction is not only related to network QoS factors, such as buffer time and buffer count, but also susceptible to the users' inclination to the contents of videos. Based on Cox regression model, we analyze the quantitative relationship between user satisfaction level in video streaming and several predictor variables such as buffer count rate, buffer time rate and video popularity degree. Experimental results prove that the model can accurately evaluate user satisfaction levels of our test video access sessions with high probability. Show less