Webinar Wire

Features: Screen Sharing

Posted by Ken Molay January 15 2008 12:34 AM EDT

1 comment

Screen sharing sometimes goes by the name of desktop sharing or application sharing. The terms are usually applied interchangeably, even though they literally describe different aspects of a similar feature.

I'll use screen sharing as the generic umbrella term. The idea is that you want your audience to see something as it appears on your computer desktop. Not just a still image, but the live full motion view so that they can see changes in real time just as you see them. One of the most frequent uses is giving demonstrations of software, although the feature has many other uses as well.

There are three common ways to let presenters choose what the audience sees. You can share your entire computer desktop, you can let your audience see a single application and nothing else, or you can let your audience see everything that falls within a defined rectangle on your screen. Some vendors give you a choice of which type of screen sharing you want to use, while other web conferencing products work in one mode only.

As with every other feature I have discussed, there are many differences in implementation between products.

The most important consideration when showing your audience live operations on your computer is the speed and smoothness of the redraw on their computers. This is a tremendously resource-intensive operation. The software has to capture every pixel on your screen, digitize it, transmit it to the audience, and reconstruct it within a frame on their computer screen. The picture is updated constantly to give the illusion of motion. The update and redraw speeds can result in something that looks natural and easy to watch, or it can give the half-drawn stutter images of a garbled satellite transmission. The worst implementations draw a still image, wait a second or two, and then redraw the next poll of your screen.

I'll single out Citrix and their GoToWebinar software as the reference standard in screen transmission performance. The entire conferencing package works in a full desktop share mode at all times, and they figured out some magic to make the updates redraw in a nice smooth motion. This is the only vendor I have seen where I feel comfortable showing a PowerPoint presentation in full screen slide share mode and trusting that my audience sees smooth animation and screen transition effects. If you want to test your vendor's performance, just create some slides with a lot of graphics on them (color gradients are a good test) and use a screen transition of "Wheel Clockwise, 1 Spoke". It should create a smooth radar sweep to redraw the next slide. Most conferencing packages break the redraw into chunks so that the concept of the animation gets lost.

Another difference in implementation is how the vendor treats their own presenter overlays while in sharing mode. While running a screen share as a presenter, you will always have some commands available to you from the conferencing software itself. Citrix is good about ignoring these areas and drawing the virtual underlying content on the audience's screen. WebEx shows their command overlays to the audience as rectangles filled with a cross-hatch pattern. I find this annoying and distracting.

If your vendor allows you to select a single application for sharing with the audience (usually selected from a list of open applications, akin to your Task Manager), you need to find out how they treat "child windows" or sub-processes of the main application. This can only be done by testing exactly what you plan to show the audience ahead of time, with a second computer logged in to your rehearsal as an attendee. Some vendors are great about showing any window that your application creates, while others show only the main application window and don't show the audience popups or spawned processes.

Speaking of popups, I have run across screen sharing implementations that won't broadcast popup "tool tips" (those little explanatory messages that many applications use to explain commands when you hover your mouse over an item). If these are important to you for training or demonstrations, make sure to test that your audience will see them.

Your screen size and resolution as a presenter is unlikely to match that of every audience member. You should do some tests to find out how your conferencing package handles differences in screen resolution. Some packages attempt to scale the shared area, some add black borders, some add scroll bars.

There are a few uncommon implementations and special features out there associated with screen sharing. One or two vendors let you share your entire desktop except for a named application. Not bad if you want to use your entire real estate, but you don't want your audience to see your email inbox for instance. A few vendors let you annotate on top of a screen share session with circles, boxes, lines, and highlighter shades. I love this advanced capability for times that I need to call the audience's attention to a specific item as I am giving a demo.

There are some cases where you want to let an audience member show his or her screen to you and the rest of the audience. Many conferencing products accomplish this by temporarily promoting that person to presenter status. Unfortunately, this may also give them additional presentation controls and access to audience names and questions that you don't want them to see. You may want to look for a product that lets audience screen sharing take place without changing their role.

Screen sharing leads naturally to some other functionality that I will cover in a separate article. Features such as remote computer control and co-browsing are complex enough to get their own topic.