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Chapter 2

SUN Hardware and Software for Videoconferencing

Introduction

 In this chapter, we describe the videoconferencing tools used in the project in some detail since we feel that this will give the reader a good idea of what constitutes a desktop videoconferencing system and will provide a reference system for comparing with other products

For this project, we used four SUN Sparcstation IPX systems, which are Sparc 2 based, and one SUN Sparcstation ZX system, which is Sparc 10 based and contains a graphics accelerator. Four of these SUN workstations were located in offices of members of staff and one on the HelpDesk. We upgraded these workstations using multimedia upgrade kits from SUN. The kits consisted of:

SUN camera
This can be attached to the top of the workstation and can swivel up and down, left and right. It has a lens shutter it is more reassuring for visitors if this is closed when the camera is being used!!
SUN video card
This takes up a single SBus slot. It is used to capture and compress and transmit video data. More details are given later in this section and in Appendix 2.
The workstations we possessed already had audio support in the form of:
SUN microphone
This could be attached to the SUN workstation. However, it was recommended that the microphone should be as far away from the speaker as possible to prevent feedback. Even if there is a separate speaker box, the microphone should be detached from the workstation since it may pick up the background hum of the workstation.
SUN built-in speaker or box
The IPX workstations have built-in speaker hardware but the ZX workstations have a separate speaker box.
The videoconferencing software required was:
SUN XIL library
This has low level functions to control applications which take advantage of the SunVideo system.
SUN ShowMe Version 2.0
More details on ShowMe are given later in this section.

The SUNVIDEO System and the XIL Programming Support

SunVideo is a real-time video capture and compression subsystem for Sun SPARCstations. It includes a SunVideo card which supports the capture, compression, storage and transmission of video images. SunVideo is designed to work with the facilities of the SUN XIL 1.1 Imaging Library which provides functions for image processing and image compression/decompression. XIL programs when used with SunVideo take advantage of the compression engine of the video card. So the compression rates are a function of the performance of the SunVideo card.

Decompression of video on a receiving workstation is done totally in software since this particular video card has no decompression functions. Applications such as Showme can access the decompression functions in the XIL library. This has the advantage that a workstation does not need a video card installed in order to receive video but the disadvantage that video performance is partly dependent on the CPU performance of the receiving host. As we found, this can be significant when the receiving workstation is a PC running an X emulator connected to a multi-user host. Please refer to Appendix 2 if you are interested in the more technical details of the SunVideo card and the XIL library.

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