Video telephony requires high-bandwidth and low-delay voice and video transmissions between geographically distributed users. It is challenging to deliver high-quality video telephony to end-consumers through the best-effort Internet. In this paper, we present our measurement study on three popular video telephony systems on the Internet: Google+, iChat, and Skype. Through a series of carefully designed active and passive measurements, we are able to unveil important information about their key design choices and performance, including application architecture, video generation and adaptation schemes, loss recovery strategies, end-to-end voice and video delays, resilience against random and bursty losses, etc. Obtained insights can be used to guide the design of applications that call for high-bandwidth and low-delay data transmissions under a wide range of "best-effort" network conditions.

Video telephony for end-consumers: measurement study of Google+, iChat, and Skype

Quality of Experience (QoE) relates to how users perceive the quality of an application. To capture such a subjective measure, either by subjective tests or via objective tools, is an art on its own. Given the importance of measuring users’ satisfaction to service providers, research on QoE took flight in recent years. In this paper we present an overview of various techniques for measuring QoE, thereby mostly focusing on freely available tools and methodologies.

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Techniques for measuring quality of experience

A method for providing cycling classes to remote users comprising providing information about available cycling classes that can be accessed via a digital communication network by a user at a remote location for display at the remote location, receiving from the user a selection of one of the available cycling classes for display at the remote location, and sending digital video and audio content comprising the selected cycling class from a server to a computer associated with a stationary bike at the remote location for display to the user on a display screen associated with the stationary bike. In various exemplary embodiments, the digital and audio content sent to the computer associated with the stationary bike is streamed for display to the user in substantially in real-time. In various exemplary embodiments, the digital and audio content sent to the computer associated with the stationary bike is archived content provided from a database.

Exercise system and method

In state-of-the-art adaptive streaming solutions, to cope with varying network conditions, the client side can switch between several video copies encoded at different bit-rates during streaming. Each video copy is divided into chunks of equal duration. To achieve continuous video playback, each chunk needs to arrive at the client before its playback deadline. The perceptual quality of a chunk increases with the chunk size in bits, whereas bigger chunks require more transmission time and, as a result, have a higher risk of missing transmission deadline. Therefore, there is a trade-off between the overall video quality and continuous playback, which can be optimized by proper selection of the next chunk from the encoded versions. This paper proposes a method to compute a set of optimal client strategies for this purpose.

Client intelligence for adaptive streaming solutions

The growth in network bitrates and server-based processing has provided a renewed opportunity for thin client games, where the server does heavy-weight computations, sending only the visual game frames to the client, and the client displays frames, sending only the user actions to the server. Understanding the traffic characteristics of thin client games is important for building traffic models and classifiers and planning network infrastructures to meet future demand. This paper provides the first detailed study of the network characteristics of OnLive, a commercially available thin client game system. Carefully designed experiments measure OnLive game traffic for several game genres, analyzing the bitrates, packet sizes and inter-packet times for both upstream and downstream game traffic, with comparisons to traditional game clients and streaming video. Results indicate OnLive rapidly sends large packets downstream, similar but still significantly different than live video. OnLive less frequently sends much smaller packets upstream, significantly different than traditional game client traffic. The results should be a useful beginning for building effective traffic models and classifiers, and for preparing end-host networks to support this upcoming generation of computer games.

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Thin to win?: network performance analysis of the OnLive thin client game system

More and more free multi-party video conferencing applications are readily available over the Internet and both Server-to-Client (S/C) or Peer-to-Peer (P2P) technologies are used. Investigating their mechanisms, analyzing their system performance, and measuring their quality are important objectives for researchers, developers and end users. In this paper, we take four representative video conferencing applications and reveal their characteristics and different aspects of Quality of Experience. Based on our observations and analysis, we recommend to incorporate the following aspects when designing video conferencing applications: 1) Traffic load control/balancing algorithms to better use the limited bandwidth resources and to have a stable conversation; 2) Use traffic shaping policy or adaptively re-encode streams in real time to limit the overall traffic.

This work is, to our knowledge, the first measurement work to study and compare mechanisms and performance of existing free multi-party video conferencing systems.

https://www.nas.ewi.tudelft.nl/people/Piet/papers/Networking2010_multiparty_video.pdf

Measurement study of multi-party video conferencing

Recently, there has been a growing interest in academic and commercial environments for live streaming using P2P technology. A number of new P2P digital Television (P2PTV) applications have emerged. Such P2PTV applications are developed with proprietary technologies. Their traffic characteristics and the Quality of Experience (QoE) provided by them are not well known. Therefore, investigating their mechanisms, analysing their performance, and measuring their quality are important objectives for researchers, developers and end users. In this paper, we present results from a measurement study of a BitTorrent-like P2PTV application called SopCast, using both objective and subjective measurement technologies. The results obtained in our study reveal the characteristics and important design issues of SopCast, as well as the QoE that the end users perceive.

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Assessing the Quality of Experience of SopCast

In recent years, a number of commercial peer-to-peer TV (P2PTV) applications have been launched. Yet, their mechanisms and characteristics are unknown. In this paper, we study SopCast, a typical proprietary P2PTV system. Treating SopCast as a black box, we perform a set of experiments that are suitable to analyze SopCast in depth. We attempt to disclose the SopCast protocol. The dynamic nature of the SopCast overlay, in terms of node degree, is also addressed in this paper. Our approaches in analyzing the SopCast mechanism and characterizing its topological properties reveal important design insights in SopCast, and may help to better understand similar P2PTV systems.

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Topology Dynamics in a P2PTV Network

Peer-to-Peer (P2P) file sharing has become immensely popular in the Internet. Recently, there has been a growing interest in academic and commercial environments for live streaming using P2P technology. A number of new P2P digital television (P2PTV) applications have emerged. Such P2PTV applications are developed with proprietary technologies and the quality of experience (QoE) provided by them is not well known. Therefore, investigating their mechanisms, analyzing their performance, and measuring their quality are important for researchers, operators and end users. In this paper, we present results from a measurement study of a P2PTV application called SopCast, using both objective and subjective measurement technologies. The results obtained in our study reveal important design issues of SopCast and the QoE that the end users perceive.

/pdf/on-the-quality-of-experience-of-sopcast-4rr7a5wdos.pdf

On the Quality of Experience of SopCast

Recently, there has been a growing interest in academic and commercial environments for video-on-demand (VoD) using peer-to-peer (P2P) technology. Unlike centralized solutions for VoD services, P2P technology lets the clients distribute video content among themselves. In this paper,we propose an analytical model for P2PVoD and we compare that model to a realistic P2PVoD simulator. With our model, parameters that affect the system performance can be observed, and the system stability can be investigated. Our model leads to design rules for achieving a good and stable system performance. This work is, to our knowledge,the first analytical work to model mesh-based P2PVoD.

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Yue Lu

Papers

Measurement study of multi-party video conferencing

Assessing the Quality of Experience of SopCast

Topology Dynamics in a P2PTV Network

On the Quality of Experience of SopCast

Analytical Model for Mesh-Based P2PVoD