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An Internet Accessible Telepresence

A.E. Kaplan, S. Keshav, N.L. Schryer, J. H. Venutolo

AT&T Bell Laboratories, Murray Hill, N.J.

{aek keshav nls jhv}@research.att.com

ABSTRACT

The US Vice President, Al Gore, in a speech on the information superhighway,

suggested that it could be used to remotely control a nuclear reactor. We don’t have

enough confidence in computer software, hardware, or networks to try this experiment,

but have instead build an Internet-accessible, remote-controlled model car† that provides

a "race driver’s" view via a video camera mounted on the model car. The remote user can

see live video from the car, and using a mouse, control the speed and direction of the car.

The challenge was to build a car that could be controlled by novice users in narrow

corridors, and that would work not only with the full motion video that the car natively

provides, but also with the limited size and frame rate video available over the Internet

multicast backbone [1]. We have built a car that has been driven from a site 50 miles

away over a 56kbps IP link using nv format video at as little as one frame per second and

at as low as 100 by 100 pixel resolution. We also built hardware to control the car using

a slightly modified voice grade channel videophone. Our experience leads us to believe

that it is now possible to put together readily available hardware and software compo-

nents to build a cheap and effective telepresence.

1. Introduction

The original motivation for building a remote-controlled car was as an application for a locally devel-

oped infrared local area network, where the car would be controlled and transmit live compressed video

over the IR network. The toy car came together more quickly that the network and other necessary parts (a

digital video imager, in particular), and so we ended up building the Internet accessible telepresence that we

describe here.

One key goal was to allow novice users to be able to walk up to a workstation and control the car,

thus the user interface required careful thought. Second, since we wanted to control the car over the Inter-

net, we wanted it to deal with slow frame rates and variable delay. To do so, we needed to highly compress

the video in order to get even a few frames per second. Third, we wanted to multicast the car’s video over

the Internet Multicast Backbone (MBONE) [1] as well as over point to point logical links. Finally, to mini-

mize effort, we wanted to reuse standard software modules as much as possible.

All of these goals were met in whole or in part in our design. The car does run over the MBONE,

and since this video is compatible with the nv program [2, 3], this video can be received by a fairly large

number of receivers. We were able to use much of the nv software and retail hardware to build the car.

However, our desire to make the presence easy to pilot, even by a user unfamiliar with it or its environment

were not fully realized. We discuss why this is so in the Section 5.

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Indice de contenidos

Pagina 1 - __________________

An Internet Accessible TelepresenceA.E. Kaplan, S. Keshav, N.L. Schryer, J. H. VenutoloAT&T Bell Laboratories, Murray Hill, N.J.{aek keshav nls jh

Pagina 2

- 2 -In the following sections, we describe the car in terms of its hardware, software and its human inter-face. Producing a plausible human interfac

Pagina 3

- 3 -Figure 2: Interface electronicsThe computer interface (Figure 2) uses the parallel printer (Centronics) port on an SGI Indigo work-station, but i

Pagina 4

- 4 -4. Network SoftwareCameraTransmitterReceiverDigitizerCompressionTransmissionReceptionDecompressionServer computerHost adaptorInternetClient compu

Pagina 5

- 5 -running on the server accepts mouse tracking and button data from the client and returns to the client a fewframes per second of software compres

Pagina 6

- 6 -relative to the car it is much more difficult to understand where the car is within the environment than itotherwise would be. We find that, giv

Pagina 7

- 7 -Internet to the capabilities provided by the car.We are aware of a few other similar projects. Some of these involve tele-operation of cameras o

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