Zon-Yin Shae

A study of Internet instant messaging and chat protocols

Instant messaging (IM) and network chat communication have seen an enormous rise in popularity over the last several years. However, since many of these systems are proprietary, little has been described about the network technology behind them. This analysis helps bridge this gap by providing an overview of the available features, functions, system architectures, and protocol specifications of the three most popular network IM protocols: AOL Instant Messenger, Yahoo! Messenger, and Microsoft Messenger. We describe common features across these systems and highlight distinctions between them. Where possible, we discuss the advantages and disadvantages of different technical approaches used in these systems to support different features and functions. We also briefly discuss ongoing efforts to standardize IM and chat-based protocols in IETF and other standards bodies

Videoconferencing over packet-based networks

The Internet explosion is driving the need for new collaboration tools which will enable two or more users to share data, audio, and video. The real-time packet-based solutions which are emerging differ considerably from the circuit-switch solutions which have existed for some time now. In this paper, we present one such packet-based approach, the Multimedia Multiparty Teleconferencing (MMT) system, which was fully implemented as a research prototype. Using MMT as an example, we address some of the fundamental issues related to videoconferencing systems in a packet-based environment, and discuss the differences with the traditional circuit-switch approaches, namely, the ITU H.320 standard. In particular, MMT is a distributed solution, while H.320 is centralized. The use of multicast and a novel video-mixing technique to facilitate the distributed solution are presented. Furthermore, MMT audio and video streams are susceptible to congestion and packet loss in the shared media packet-based environment, while H.320 streams use dedicated connections. As such, synchronization, error resilience, and dynamic rate control schemes for the packet-based system are presented.

A multimedia desktop collaboration system

Desktop multimedia conferencing, which can enhance the quality of collaboration between remote participants, is considered. The architectural and implementation issues involved in the design of such an application are discussed. A prototype desktop conferencing system is presented. It provides a multiparty collaborative environment which integrates high-quality video and audio with a shared workspace manager. Some of the distinguishing features of this system are the flexibility to support various types of collaboration, full-motion (30-frames/s) video, support for multiple video windows, and unconstrained audio. The shared workspace manager allows existing X-windows applications to be used concurrently by the participants in the conference.<<ETX>>

On multipoint control units for videoconferencing

This paper examines the issues involved in the design of conference servers that support multiparty, multimedia conferences. These servers, called multipoint control units (MCUs) in the telephony world, coordinate the distribution of audio, video, and data streams amongst the multiple participants in a videoconference. The MCU is responsible for the processing of video and audio so that a conference participant can hear and see one or more of the other participants in the conference. It is also responsible for handling and forwarding the data streams from the participants. This paper presents different approaches to the design of an MCU to implement these functions. It also describes the design of a related device-a transcoding gateway that enables conferencing between participants using different video/audio equipment.<<ETX>>

Virtual machine migration in an over-committed cloud

While early emphasis of Infrastructure as a Service (IaaS) clouds was on providing resource elasticity to end users, providers are increasingly interested in over-committing their resources to maximize the utilization and returns of their capital investments. In principle, over-committing resources hedges that users - on average - only need a small portion of their leased resources. When such hedge fails (i.e., resource demand far exceeds available physical capacity), providers must mitigate this provider-induced overload, typically by migrating virtual machines (VMs) to underutilized physical machines. Recent works on VM placement and migration assume the availability of target physical machines [1], [2]. However, in an over-committed cloud data center, this is not the case. VM migration can even trigger cascading overloads if performed haphazardly. In this paper, we design a new VM migration algorithm (called Scattered) that minimizes VM migrations in over-committed data centers. Compared to a traditional implementation, our algorithm can balance host utilization across all time epochs. Using real-world data traces from an enterprise cloud, we show that our migration algorithm reduces the risk of overload, minimizes the number of needed migrations, and has minimal impact on communication cost between VMs.

Distributed video conferencing systems

The emergence of the Internet as a global communications infrastructure has enabled the development of new distributed multiparty video conferencing solutions. These distributed solutions differ considerably from the circuit-switched centralized approaches which preceded them. In this paper we discuss these differences from a general perspective and then describe an actual distributed multiparty solution. The multimedia multiparty teleconferencing (MMT) system implemented at the IBM T.J. Watson Research Center is a high quality video conferencing solution that runs over an IP network. The solution addresses multicast, synchronization, video mixing, error handling, and directory service issues. A detailed description of a solution for secure video conferencing through corporate firewalls is presented.

Mixing and playback of JPEG compressed packet videos

Video mixing, which is the simultaneous display of multiple motion videos received from multiple independent sources across a packet switched network, is addressed. A straightforward approach, which performs mixing at the pixel level, is analyzed and found undesirable because of the requirements of large amount of expensive memory and decompression capacity. A technique that performs direct mixing of JPEG compressed data is introduced. An efficient structure based on this technique, which needs only a frame worth of buffering and decompression regardless of the number of video windows and their sizes, is presented. Packet video playback is discussed, and two simple heuristics are proposed.<<ETX>>

CSR: Speaker Recognition from Compressed VoIP Packet Stream

VoIP applications require the ability to identify speakers in real time. This paper presents compressed speaker recognition (CSR), an innovative approach to perform speaker recognition directly from the compressed voice packets. CSR performs online speaker recognition from live packet streams of compressed voice packets by performing fast clustering over a defined subset of the features available in each compressed voice packet. Our experimental results show that CSR is highly scalable and accurate across a broad range of speakers

Realistic video avatar

We present a system for the implementation of a photorealistic avatar using video captured from a user. This is achieved by constructing the dynamic video texture map and combining it with the 3D mesh model of the user to render the photorealistic avatar. The dynamic video texture map reflects the users facial expressions and is generated by composing the cylindrical texture map of the user with constant updates either directly from the input video or derived from a temporal and spatial interpolation scheme. To derive the 3D mesh model for the user, we define feature points on a generic model and use the feature points identified on the video sequence to deform and obtain the avatar model. The goal of this realistic video avatar project is to provide a vivid representation of participants with a more realistic quality avatar, as compared to using only the facial animation parameters defined in MPEG-4 without the corresponding image updates. This scheme is suitable for conferencing applications because it requires much lower bandwidth than live video, and yet provides a 3D avatar representation for any virtual environment.

Robust H.263 video coding for transmission over the Internet

The widely popular World Wide Web along with advances in desktop computers has brought the world into a new age of computing and communications. Low bit-rate video applications across the Internet are quickly emerging. The ITU-T H.263 standard was designed for low bit-rate video conferencing across phone lines and is an ideal candidate to be extended for Internet video applications. This paper focuses on the error robustness issue of compressed H.263 video streams when transmitted over the Internet. The traditional approach of inserting intra-coded frames increases the error resilience at the expense of bursty output traffic, lower picture quality, and uneven frame dropping. By extending the macroblock force update feature of the H.263 standard, we developed a scheme that complies with the standard and increases the robustness of the video stream. This macroblock updating scheme analyzes the temporal dependencies of macroblocks in successive frames and selectively updates the macroblocks which have the most impact on later frames. The performance evaluation of the proposed technique demonstrates that it achieves a good balance between error recovery speeds and video quality.