Transcript The Access Grid - Florida State University

Changyun Wang
Under the Supervision of Dr.Turner
The Access Grid is an Internet-based model for video
conferencing developed by the Future Lab(FL)within
the Mathematics and Computer Science (MCS)
division of Argonne National Laboratories(ANL)
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Basic functionality

An access Grid “node” is a conference room or small auditorium
provisioned with the equipment to participate in a multipoint video
conference.
. Audio
. Video
. Whiteboard
. Screen sharing
. Application
Functionality
The basic functionality provided within the node is:
. Audio: encoding using one or more microphones (via a mixer)
. Video: encoding or “capture” using one or more cameras
. Audio presentation using one or more speakers
. Video display via one or more computer monitors and/or
video projection techniques
. Display of PowerPoint “slides” under the control of presenter
located either on-site or at a remote site.
. Screen sharing/whiteboard via VNC.

Software components
The Access Grid model revolves around two pieces of
software:
•vic: the video conferencing tool, and
•rat: the robust audio tool.
and involves several other applications
•Distributed PowerPoint
•a MUD
•the Multicast Beacon
•Virtual Venue
•Virtual Network Computing
Software components
vic and rat were developed as part of the Internet Multicast
backbone, or MBONE, which provided multicast services
over the unicast Internet backbone (using "tunnels", or
"bridges", between multicast nexus sites).
The Access Grid model relies upon the ability to send and
receive Internet Multicast traffic to and from all conference
nodes.
An individual vic stream will generate from 10Kbps to
4Mbps of network traffic. A large conference may generate
20Mbps.
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Video Conference(vic)
Vic was developed by Steve McCanne and Van Jacobson at the
Lawrence Berkeley Labs. It is intended to link multiple sites with
multiple simultaneous video streams over a multicast infrastructure.
vic CAN perform 2 basic functions:
• take data from video capture cards in the PC to which cameras
(or other video devices) are attached and send it over the
network.
• receive data from the network and display it on a video monitor
or on some other attached video device such as a video projector.
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Robust Audio Tool(Rat)
rat is a recent version of the Visual Audio Tool, also developed by
Steve McCanne and Van Jacobson at the Lawrence Berkely Labs.
rat allows multiple users to engage in a audio conference over the
Internet in multicast mode. rat can perform 2 basic functions:
• take data from the sound card in the PC to which microphones,
headphones, or some other audio devices are attached and send it
over the network.
• receive data from the network and send it to speakers,
headphones, or other attached sound processing device, such as a
tape recorder, etc.
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The MUD software
Operators at each site involved in an Access Grid conference typically
keep in touch by using software originally developed for online
"role-playing" games generically called Multi-User dragons and
Dungeons" games, or "MUDs". (MUD functionality is similar to
that of Inter net Relay Chat operating with access control.)
Argonne runs a MUD server for use by Access Grid operators who run
MUD clients on their desktop systems. tkMOO-lite is currently the
recommended MUD client for this purpose, but others, such as
Tiny-Fugue in the Unix environment can be used as well.
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The Multicast Beacon
To help diagnose multicast network problems during conferences,
Argonne promotes the use of the NLANR multicast "Beacon"
monitoring system, which includes three pieces of software:
• a Beacon to be run at each AG node,
• a server to collect transmission statistics from a collection of
Beacons, and
• a Beacon viewer that displays data collected by the server.
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The Virtual Venue software
Coordinating multiple group conferences can be complicated. Argonne
has developed a collection of web pages and Java applications that
can simplify the process.
The Virtual Venue is basically a web-page that lets users select a
"conference" to attend. In this context a "conference" is composed
of
• a vic multicast address,
• a rat multicast address, and
• a MUD identifier.
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The Virtual Venue software
If your systems are Virtual Venue-enabled, the display system operator
can click on a conference room name and the vic, rat and MUD
applications running on the video display, video capture and audio
processing systems will all be started with target addresses and
settings appropriate to the selected conference room.
This coordination is accomplished by running an "event server" and
the event controller on the display system, along with "event
listeners" on the video capture and audio processing systems.
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Virtual Network Computing
• VNC allows users to share monitor screens over the Internet in a
variety of modes. In the Access Grid environment, VNC allows a
speaker to share his/her podium laptop with Access Grid display
systems which can then project it at remote nodes. This is useful
when a speaker wishes to give real-time demonstrations or present
PowerPoint slides that include "fancy" features, such as animations,
that cannot be displayed using Distributed PowerPoint.
• VNC employs a client server architecture, and there are clients and
servers available for Windows98/NT/2000 and Unix operating
systems.
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Basic system configurations
• The AG model uses a collection of commodity components to
provide various services. To assure optimal responsiveness
individual functions (video capture, video display, audio capture and
presentation) are placed on separate computer systems.
• There is a variety of hardware and software configurations that can
provide the required video conferencing functionality.
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Here is one possible configuration:
• 1 computer system running Linux for audio capture and
presentation
• 1 computer system running Linux for video capture
• 1 computer running Windows2000 for video display through 1 or
more video cards
• 1 audio echo-canceller/mixer (e.g., Gentner AP400)
• 1 computer system running Win98 for controlling the echocanceller
• 1 speaker's podium computer running Windows2000 or NT to
control remote PowerPoint displays and/or give real-time
Windows-based demonstrations
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The Gentner AP400 Echo Canceller
• Within the Access Grid model, signals from and to attached audio
equipment are funneled through an "echo canceller" made by the
Gentner Communications Corporation, to eliminate certain kinds of
echoes produced during networked conferencing.
• It is probably fair to say that the Gentner echo canceller is the major
component of the audio conferencing system Networks of Gentners
work together to provide useful audio signal exchanges.
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The Gentners can use 3 different connectivity infrastructures:
•a point-to-point telephone connection,
•a telephone connection to a telephone bridge (used as a
backup during some conferences),
•a computer network, or
•Gentner's own local area network, called G-link.
When a Gentner uses a computer network to connect to other
Gentners, it connects to the computer just as it would to a simple
Codec (compression/decompression device).
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Echo Canceller control computer
• The audio control computer runs Windows 98 and uses custom
Genter Control Software to control the Gentner mixer/echo
canceller. See http://www.gentner.com for more details.
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Audio capture and presentation computer
The audio capture computer:
• Converts analog audio from mixers and mics to digital form for
transmission by rat over the multicast network
• Converts digital audio to analog audio for distribution to room
speakers and/or headsets .
Software
• RedHat Linux version 7.n
• rat
• AudioResourceManager from the Virtual Venue suite
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Video capture computer
The video capture computer system converts analog video from
cameras and/or VCRs, etc. to digital for transmission by vic over the
multicast network.
Software
• RedHat Linux version 7.n
• Stock kernel with the BTTV drivers
• vic
• VideoResourceMonitor from the Virtual Venue suite
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Video display computer
Receives video content over the network and displays it on the PC
monitor as well as one or more other monitors and/or video
projectors if desirable (using the ability of Win2K to display its
console screen across multiple video cards)
• Decodes Video streams
• Runs collaboration applications such as Distributed PowerPoint
and the VNC viewer
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Software on the video computer
. Windows 2000
• vic
• PowerPoint
• Argonne Distributed PowerPoint client
• EventServerMonitor and DisplayResourceManager from the
Virtual Venue suite
• VNC viewer
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Speaker’s podium computer
The speaker's podium computer runs:
•
•
•
•
Windows98/NT/2000
PowerPoint
the Argonne Distributed PowerPoint master software, and the
VNC server
Configuration suggested by Argonne: Some laptop powerful enough to
run PowerPoint
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References
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www.cc.ku.edu/acs/docs/access-grid-node/access-grid-ku.html
http://www.osc.edu/accessgriddoc/room/roomconfig.html
http://mrccs.man.ac.uk/global_supercomputing/hardware.html
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