The mode of use of workstations in MICE

A multimedia workstation typically allows a single person to communicate with external partners. Workstations are located at a working place and have lower-quality technical equipment than conference rooms. Conference rooms will be described elsewhere. here we focus on the INRIA Videoconferencing System (IVS).

The INRIA Videoconferencing System (IVS)

IVS is designed with the explicit goal to demonstrate that it is possible today to use a standard workstation for video/audio conferences. Thus, in order to conduct a videoconference with IVS, only minimal hardware upgrades are required to a machine commonly found on the desk of an engineer, namely a video camera and a frame grabber.

IVS allows to use standard Internet technology to transmit video/audio-data. This is achieved by implementing PCM and ADPCM audio codecs and a software version of a H.261 codec (video codec for audiovisual services at p*64 kb/s).

Furthermore, where conventional H.261 hardware codecs require leased lines or switched circuits for data-transmission, the H.261 software codec of IVS uses standard UDP datagrams. Minimal changes are required to use this coding on packet switched networks such as the Internet. A packetization scheme of H.261 video stream has been designed and is described in an Internet Draft submitted to the Audio Video Transport Working Group at the IETF. Both IVS and hardware codecs such as GPT and Bitfield use this packetization scheme, so interoperability is now possible.

IVS also includes an error control scheme to handle packet losses in the Internet. Version 3.3 of IVS includes a feedback rate control scheme which adapts the image coding process, and hence the output rate of the coder, depending on network conditions. The feedback information is periodic loss-rate measurements sent back from decoders to the coder.

IVS runs on several UNIX platforms such as SPARC, Silicon Graphic, HP and DEC stations. Sources and binaries are freely available in the public domain by anonymous ftp from zenon.inria.fr at the URL

Multimedia trends in workstation design

Virtually every workstation manufacturer is making multimedia offerings. MICE have used several of the current desgins of workstations in Phase I of the project An add-on workstation board can now perform the codec (video compression and decompression) functionality for approximately 3,000 ECU (3,000 USD), so that with a modern workstation, the decoding can be done in software. The requirement for 50 Mips is easily available these days. It is only for high bandwidth good fidelity, that dedicated hardware codecs are still needed.

This figure shows a fairly typical workstation configuration.

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