For Multicast seminars, it is always preferable to share slides with the help of a shared/collaborative workspace tool. The tools wbd or wb are the most widely used in this instance, however the constraints with these are that they do not allow the importing of images other than those saved in postscript and the tools are not particularly easy to use for a novice user. The advantages however are that the bandwidth used by the tools is considerably lower than many other methods, especially if the pages are cached in advance, and the clarity of the images is perfect. For further information about preparing slides for display using WB/WBD or NTE please read this document. 
For multicast seminars which are also being received by sites through a multicast to unicast/ISDN/ATM gateway, shared workspace data cannot be relayed. If the site is capable of receiving/displaying unicast traffic then there are a number of alternative shared/collaborative workspace tools which are discussed in turn below. The backup option (this should always be considered as a secondary option in the event that none of the above are possible) is to transmit the slides as a separate video stream:-

• Webcanal - Shared Web Browser. The advantage of this tool is that it is supported on any platform which has the JDK 1.1.x (Java Development Kit) installed. In addition to which it has a caching facility which enables sites to download web pages in advance of a session. Since the URL of the slides is posted to all the participants in a session, the actual data is not sent from the controlling client, but each client requests the data separately from the web server. It uses a unicast connection to connect to the webconf server which can run on any platform.

This product is available as freeware and can be downloaded from this site. Requires thorough testing before it can be recommended for large scale deployment.
• WhitePine Board - This is a shared workspace tool developed by the creators of CU-seeme and is available as freeware. The Whitepine Board provides a very intuitive user interface and supports the display of high resolution images with open access to all session participants. The disadvantage is that it can only be used on windows 95 platforms. It has been installed and tested on Windows 98 at UCL however the developers, who are no longer working on the product, have clearly stated that it is not supported under windows98 or NT. One site initiates a conference, and other participants join via a unicast connection to the session. It does not potentially scale well under a widescale distributed conference with many participants, however it has many interesting features which could be a great benefit to small group conferences.

This product is available as freeware and can be downloaded from this site. Requires thorough testing on Windows 98/NT platforms before widescale use.
• MWhiteboard - part of the Marratech Pro suite. The product is proprietary and as yet no testing has taken place. However, initial impressions are quite favourable, and the product has great potential. It is currently only supported on the Windows95/98/NT platforms. For further information visit the Marratech Pro website. Further testing is anticipated between certain PIPVIC-2 project sites in the near future.

This product is available for a 30 day free trial from this site. Only supported on Windows platforms.
• PCAnywhere - This an application which enables one site to share a windows95/98/NT desktop with any number of users via a unicast link to each client. This is potentially a very useful tool for displaying full screen powerpoint presentations. The refresh rate and image clarity are excellent with this product, however it is important to be aware that when large amounts of data are being transmitted, PCAnywhere can potentially cut out audio or video transmission coming from the same machine. No measurements of bandwidth or CPU usage have so far been made. Further testing is planned, however it has been noticed in recent tests that as the number of connections to the server increases the load induced on the machine seems to slow down the data output rate to all the clients. Further testing is scheduled.

This product is available for a 30 day free trial from this site. Only supported on Windows platforms.
• PCDuo - similar functionality to PCAnywhere. Seems to provide better colour display with similar refresh rate.

This product is available for a 30 day free trial from this site. Only supported on Windows platforms.
• VNC - Viewer/server. Research project software, produced originally by the Olivetti Research Laboratory, but now under the auspices of AT&T. This software has very similar functionality to both PCDuo and PCAnywhere but is cross platform (both Windows and Unix based platforms). The refresh rate is quite slow, and the server setup to enable multiple connections is not as intuitive.

This product is available as freeware from this site.
• Netmeeting Data Sharing - This is part of the Microsoft Netmeeting freeware product. It allows one machine to host a session to which other participants can connect via a unicast link. It will display images at the highest possible resolution which all machines in a session can support, and is a well supported product. The disadvantages are that it doesn't appear to exercise much bandwidth control during a session and can create large bursts of network traffic which will adversly affect other tools in a session. If running on the same machine as other audio and video tools, it could potentially have an effect on their performance. Widescale use in project activities is anticipated and therefore further testing is anticipated.

The latest freeware version of Netmeeting is available from this site. It is only supported on Windows platforms.
• Slide Transmission as a video stream. This is the most bandwidth intensive method of transmitting slides to conference participants. In addition to which, the clarity of images can be severely reduced depending upon the nature of the equipment used. The general method for sending slides is by using a scan convertor connected to a PC laptop from which the speaker displays a powerpoint demonstration. The image is then fed into a framegrabber card in a machine which transmits the image using vic or an equivalent video tool. Scan convertor equipment is required, as is a machine with either dual framegrabber cards (or two separate machines with single cards in each) to be able to transmit the speaker's image in addition to the slides or a video switch to flip between the two sources during the talk. A cheap alternative to buying a scan convertor is to use the Luminositi Softcam video driver which provides a moveable/resizable transparent window on a windows95/98 (not NT) desktop to grab any images contained within the area and transmit it as a video source. The disadvantage of this is that the resolution of this is not very high, and the resultant picture quality received by other participants is not very clear. The 30 day shareware driver is available from the Luminositi website. Another option for transmitting slides as a video stream is from a document camera, although again the degradation of the quality seen from the original slide can be quite high.

As a general indication:- 

• Slides should not contain text any smaller than size 30
• Titles should be approx size 44
• Any information which requires more than 8 lines of subheadings would be better displayed on two or more slides.
• Animation in presentations is, in many cases, difficult to convey. Static slides are a safer way of ensuring that information is correctly received by all participants.