George Politis

George Politis

London, England, United Kingdom
354 followers 355 connections

About

Senior software engineer with 10 years of work experience in component-based design…

Publications

  • Considerations for deploying a geographically distributed video conferencing system

    2018 IEEE 8th Annual Computing and Communication Workshop and Conference (CCWC)

    In this paper we report on our ongoing work to improve the user experience of video conferencing by using geolocation. We discuss the problem of selecting a media server for a video conference, introduce one state-of-the-art system which uses a simple method, and discuss a model for distributing a conference among a set of media servers. We perform a measurement study of a production service, and find that in many cases, contrary to common wisdom, connecting each participant to their closest…

    In this paper we report on our ongoing work to improve the user experience of video conferencing by using geolocation. We discuss the problem of selecting a media server for a video conference, introduce one state-of-the-art system which uses a simple method, and discuss a model for distributing a conference among a set of media servers. We perform a measurement study of a production service, and find that in many cases, contrary to common wisdom, connecting each participant to their closest server is not only costly, but counter-productive in terms of decreasing the round-trip time. While, the approach may still seem viable in some use cases, more research is needed in order to understand when that may be, and define specific algorithms for server selection in the case of a distributed media conference.

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  • Experimental Evaluation of Simulcast for WebRTC

    IEEE Communications Standards Magazine

    One of the important use cases for WebRTC is multi-party audio/video conferencing, and there are multiple services that offer that functionality. Two aspects that the maintainers of such services often try to optimize are the maximum size of their conferences, and the cost of their infrastructure. Simulcast is one approach to addressing these problems in conference systems that build upon video routers. It consists of the simultaneous transmission of multiple versions of a participant's video…

    One of the important use cases for WebRTC is multi-party audio/video conferencing, and there are multiple services that offer that functionality. Two aspects that the maintainers of such services often try to optimize are the maximum size of their conferences, and the cost of their infrastructure. Simulcast is one approach to addressing these problems in conference systems that build upon video routers. It consists of the simultaneous transmission of multiple versions of a participant's video stream, which use different resolutions, frame rates and, most importantly, different bit rates. In this article we present the analysis and experimental evaluation of a conference system based on WebRTC using simulcast with the VP8 codec. We examine the computational and bandwidth requirements of both the server and the clients, as well as the end-to-end video quality. Our results show significant gains for the receivers and the infrastructure, with minor penalties to the image quality and resource usage for the senders.

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Patents

  • Dynamic adaptation to increased SFU load by disabling video streams

    US US9712570B1

    A method for dynamically adapting to increased system load at a selective forwarding unit (SFU) is disclosed. In an embodiment, an SFU sends a plurality of video streams to a plurality of participant computing devices. The SFU monitors a system load value on the SFU according to any of a plurality of metrics. When the SFU determines that the monitored system load value exceeds a stored load threshold value, the SFU selects one or more of the streams being sent to participant computing devices…

    A method for dynamically adapting to increased system load at a selective forwarding unit (SFU) is disclosed. In an embodiment, an SFU sends a plurality of video streams to a plurality of participant computing devices. The SFU monitors a system load value on the SFU according to any of a plurality of metrics. When the SFU determines that the monitored system load value exceeds a stored load threshold value, the SFU selects one or more of the streams being sent to participant computing devices and disables them.

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  • Multiplexing sessions in telecommunications equipment using interactive connectivity establishment

    US US9674140B1

    A data processing method comprising generating, by each Interactive Connectivity Establishment (ICE) endpoint of a plurality of ICE endpoints, a username comprising an identifier, wherein the plurality of ICE endpoints are accessible through a single Internet Protocol (IP) address and port number pair; sending, by each ICE endpoint, at least the username to a server for use in establishing a session between a specific ICE endpoint of the plurality of ICE endpoints and a client device;…

    A data processing method comprising generating, by each Interactive Connectivity Establishment (ICE) endpoint of a plurality of ICE endpoints, a username comprising an identifier, wherein the plurality of ICE endpoints are accessible through a single Internet Protocol (IP) address and port number pair; sending, by each ICE endpoint, at least the username to a server for use in establishing a session between a specific ICE endpoint of the plurality of ICE endpoints and a client device; receiving, at a proxy associated with the plurality of ICE endpoints, a datagram from the client device for the specific ICE endpoint, wherein the datagram comprises the username; in response to attributes of the datagram not matching an entry in a table of the proxy, extracting the identifier from the username; forwarding, by the proxy, the datagram to the specific ICE endpoint based on the identifier.

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  • Rapid optimization of media stream bitrate

    US US20180097863A1

    A data processing method comprises, using a media server during a first media session between a client device and the media server, determining a stable bitrate value for use as a rate of transmitting multimedia data from the client device to the media server; storing, in a database, the stable bitrate value for the client device in association with an identifier; receiving, from the client device, a request to establish a second media session; determining the identifier within the request; in…

    A data processing method comprises, using a media server during a first media session between a client device and the media server, determining a stable bitrate value for use as a rate of transmitting multimedia data from the client device to the media server; storing, in a database, the stable bitrate value for the client device in association with an identifier; receiving, from the client device, a request to establish a second media session; determining the identifier within the request; in response to the request, based on the identifier in the request, searching the database for the stable bitrate value that is associated with the identifier; in response to locating the stable bitrate value in the database, sending the stable bitrate value to the client device for use in estimating a bitrate for transmitting multimedia from the client device to the media server in the second media session; establishing, by the media server, the second media session, wherein the media server initially receives multimedia data from the client device at the stable bitrate.

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Projects

  • jitsi-videobridge

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    Jitsi Videobridge is a WebRTC compatible video router or SFU that lets build highly scalable video conferencing infrastructure.

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  • otr4j

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    otr4j is an implementation of the OTR (Off The Record) protocol in java. Its development started during the GSoC '09 where the goal was to add support for OTR in jitsi. It currently supports OTRv1, OTRv2 and OTRv3.

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  • sdp-interop

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    A JavaScript library that provides a translation layer for converting Unified Plan SDP to Plan B SDP and visa-versa.

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