Screen sharing is one of the core tenets of web conferencing, yet to the vast majority of users, knowing how to screen share with confidence remains a mystery. How many times have you been in a meeting and heard a presenter ask, “Can you see my screen?”. Likewise, how many of you have wondered if everyone can truly hear you when using Voice-over-IP?

Latency and fidelity are the two areas where presenters most often come across challenges when performing higher bandwidth activities such as screen sharing, VoIP, broadcasting live video and playing back pre-recorded video and Flash Applications. Latency, by definition, refers to the amount of time it takes for information to travel from your computer to each attendee’s computer. Sometimes when users share their screen or broadcast VoIP, other meeting attendees can experience a high degree of latency, or a situation where a noticeable time lag occurs between when the presenter performs an action on their desktop or says a word and when that action is seen or heard by meeting attendees. Fidelity, on the other hand, is the accuracy with which an image is reproduced from the presenters screen or in the case of audio, how pristine the audio sounds.

When hosting a meeting, it is your responsibility to properly manage a balance between latency and fidelity to ensure a great meeting experience for your attendees. Whether you are using Voice-over-IP, broadcasting webcam video, or sharing your screen, you need to be very aware of the amount of data you are pushing over to your audience. Not doing this can quickly result in dropped audio, choppy video, or screen sharing that is lagging far behind. Luckily, Adobe Connect has a few tools to help you in this task.

Optmize Room Bandwidth Settings

Adobe Connect has two room settings available for meeting attendees to optimize meeting performance. One is a global setting set by the meeting host and the other is a per-user setting that each participant can set individually.
First, meeting hosts can control the overall room bandwidth setting. Using this setting in conjunction with the latency information displayed in the participant list allows you to push the highest-quality screen fidelity to your audience. To change overall room bandwidth, select Meeting > Preferences then select the Room Bandwidth section.

Fig 1. Correctly setting the room bandwidth is an essential step to enabling a great meeting experience for your attendees.

In this dialog are three settings available for the most common bandwidth scenarios: Modem, DSL/Cable, and LAN. If a meeting host chooses LAN over DSL/Cable or Modem, the fidelity of the screen image or audio stream will be better, but with more bandwidth required and a higher chance of users on slower connections experiencing a higher degree of latency.

Therefore, it is important to know your audience’s connection speed. A general rule of thumb is if you are meeting with a purely internal audience who are all connected locally on a T3 LAN, you likely want to maximize your fidelity since bandwidth is not much of a concern. If you are meeting with a highly diverse external audience who are attending the meeting on a variety of connections, it’s probably a good idea to lower the room bandwidth settings to DSL or Modem to ensure that users do not experience latency.

Similarly, meeting attendees can set their personal bandwidth setting through the Meeting menu. This setting is applied to a particular attendee’s experience. If an attendee sets their bandwidth setting to DSL/Cable and the meeting room bandwidth is set to LAN, the information sent to the attendee’s computer is tailored to their specified connection speed. If you are running a meeting with an attendee who is experiencing latency issues, instruct them to change this setting.

Bandwidth Distribution with Screen sharing, VoIP and live video

In this section, I discuss how bandwidth is considered when multiple bandwidth-intensive features such as screen sharing, voice over IP (VoIP), and live webcam video are being used simultaneously. If you won’t be sharing live video or using VoIP, you may want to skip this section, as it can get complicated. However, if you are an advanced user of the system who wants to squeeze the last bit of performance out of Adobe Connect, this section will help you achieve that.

When a meeting host is using screen sharing along with VoIP and live video with the Camera and Voice pod, a lot of information needs to be transmitted from computer to computer. To account for this, Adobe Connect has a sophisticated scheme for handling scenarios where individual meeting participants have constrained bandwidth, and to decide how to keep users from falling too far behind while still having a good meeting experience. Adobe Connect broadcasts simple meeting events like slide changes and chat first, then voice, then screen sharing, then live video.

To describe how this works in a real-world scenario, let’s say a meeting is being conducted with video (at 50 Kbps), voice (at 22 Kbps) and screen sharing. A host and two participants are in the meeting. Here is how Connect Pro prioritizes the various streams to ensure an optimal experience.

	Lisa is hosting the meeting on a corporate LAN that supports a 10 Mbps connection, so Adobe Connect has a lot of bandwidth to play with. Even if Lisa is sharing her screen at a 1600x1200 pixel resolution and showing a slide show of colorful snapshots from the company party, there is plenty of bandwidth to broadcast her screen with little or no effect to her video and audio streams. If all users in the meeting are on this type of connection, Adobe Connect does have a feature called Turbo Screensharing for extreme screen sharing that is turned off by default. However, be forewarned that this feature is intended only for those customers with high-bandwidth networks. This setting would do a good job of filling that 10 mbps connection to capacity with beautiful, high-fidelity renditions of Lisa’s Christmas pictures.
	Dawn is a meeting participant attending from home on a 500 Kbps DSL connection. In this scenario, 22 Kbps are used for voice and 50 Kbps are used for video, leaving 428 Kbps for screen sharing. If the changes on Lisa’s screen are small, or if the screen is displaying mostly text, the screen-sharing experience is flawless. But if Lisa suddenly presents a full-screen picture of the Christmas party that represents 3000 Kbps of information, Adobe Connect freezes the live video stream, leaves the audio stream alone, and uses 478 Kbps for several seconds to re-render Dawn’s view of Lisa’s screen. After the screen is redrawn, Adobe Connect unfreezes the live video stream back to its normal state. Because screen sharing is almost always more important than live video, Adobe Connect always takes bandwidth from live video in favor of screen sharing to optimize the experience.
	Marty is participating in a meeting from his home with a 48 Kbps modem. If 22 Kbps are used for the voice, that leaves only 26 Kbps for video and screen sharing (Adobe Connect does require some bandwidth to keep the basic meeting running, but it is negligible enough to ignore for this example). When an event happens that must be rendered by Marty’s computer, such as Lisa moving a picture around on the screen, Connect Pro automatically freezes Lisa’s live video stream in Marty’s view until the screen sharing catches up to Lisa’s computer. When the updated screen-sharing image is finished rendering, Connect Pro compresses the live video stream and ignores frames to squeeze the 50 kbps live video stream into the remaining 26 Kbps. Because voice is typically most critical for a smooth meeting experience, Adobe Connect preserves the fidelity of the audio stream and reduces screen sharing and video fidelity to keep the audio smooth.

Summary

I cannot emphasize how important it is to set correct room bandwidth to ensure your meeting runs smoothly. Using this feature will enable you to maximize meeting fidelity while minimizing latency. Hopefully in this tutorial, you've learned some new techniques for how to better manage meeting bandwidth in a way that is intuitive to use. As the meeting host, you are the only one who has the power to use these tools and in turn, provide a great experience for your attendees so they can focus on what really matters: the content and discussion in the meeting itself.

(Special thanks to David Yun - the author of the original article.)