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IVN Users' Guide

Contents
  1. Introduction: About IVN and this guide
  2. Setting Up Your System
  3. Making Calls
  4. Scheduling a Session
  5. Tips on Using IVN
  6. Tips on Using the IVN Web Page
  7. Frequently Asked Questions
  8. Getting Help

Introduction: About IVN and This Guide

IVN

Welcome to IVN, the University System of Maryland's Interactive Video Network! IVN's primary purpose is to provide the infrastructure for distance education for schools in the State of Maryland. IVN also provides support for intra- and interstate educational, administrative, and training events that can benefit from videoconferencing.

The IVN staff are available to help troubleshoot any trouble users may have. The staff strongly recommends that all new endpoints test their connection to the bridges. Also, if a call is planned with an outside organization, we recommend performing a test call beforehand, to make sure there aren't any problems. Contact us to schedule a test call.

Using This Guide

This guide is intended to help a wide audience use the IVN system. It touches on many topics, some very straightforward, others obscurely technical. It tries to answer as many questions as possible in one place; however, there is no reason for any given reader to worry about reading all of it. IT staff setting up a new system will want to read "Setting Up Your System," but professors using the system or administrators managing the schedule need not bother; the system should be set up for them, and they need only concern themselves with making calls and scheduling conferences. Because not every reader will read the whole guide, if read from beginning to end, some information will be repeated.

An Overview of Videoconferencing

Videoconferencing is a combination of technologies that allow two or more locations to interact visually and audably in real time. In simple terms, everybody can see and hear each other. This makes it possible to hold meetings, give presentations, and teach classes to people in different buildings, campuses, states, or continents.

A teleconferencing setup has a few basic components. It requires a monitor or television screen to see the other location or locations in, speakers to allow them to be heard, a camera to send video out, microphones to send out audio, a connection to the network, and the endpoint to bring everything together.

Videoconferencing sites call each other, just like one would with a telephone. During a call, each site sends its picture and sound for others to see and hear, just like a telephone sends your voice during a phone conversation. Using a bridge, multiple callers can join in the same conversation; the bridge mixes the audio together and arranges the video on the screen. Most endpoints can also take video from a computer or a document camera, allowing presenters to share documents and presentations.

Technical Note: Understanding Compressed Audio and Video

Uncompressed full motion video requires a lot of bandwidth, or space on the network. Many locations do not have the bandwidth to spare for that. So video sessions use "compressed video." Compression simply means sending a smaller amount of data to get your information across; sometimes this means just squishing your data down, and other times it means picking what information to send and what to leave out. Video compression has three main components. The first is in the picture itself; using a complicated set of rules, the picture is cut into squares whose individual quality is reduced in ways that do not bother the human eye more than is necessary. If you have ever converted your pictures from some other format to JPEG (.jpg), you have done exactly the same thing; your picture doesn't look very different, but suddenly it uses a tenth as much space as it did before. The second component involves sending only what information needs to be sent. If part of the picture does not change, then there's no reason to re-send it. And the last component is to send less detail when there's a lot of information to send (because the image has changed a lot, such as when things are moving around a lot or the sender has changed cameras) and to go back and fill in the detail when the image isn't changing so much. The less bandwidth that is allocated to the call, the more obvious these effects will be.

If you have ever watched digital television, you have seen, though possibly did not notice, the side effects of video compression before. Satellite, digital cable, DVDs, and HDTV all use the same compression techniques as teleconferencing, albeit at the equivalent of very high data rates. (As a comparison, most IVN conferences have a data rate of 768kbps, or 768,000 bits per second; a standard definition DVD has a data rate of 10.5Mbps, or 10,550,000 bits per second.) The effects are even more noticable when something goes wrong in the connection; part of the screen may contain odd-looking blocks, or part of somebody's moving arm may appear to stay in place. Fortunately, the vdieo compression protocol occasionally sends an update of the full screen just to be sure everybody is on the same page, so these should not last more than a few seconds.

Audio takes up a lot less bandwidth than video, but audio compression has been around longer and there are some very advanced methods of doing it. Some methods compress audio along the same lines as MP3s for songs, using principles very similar to the video compression (removing nuances to the sounds that the human ear won't miss much, for example); others concentrate on specifically handling voices, even going so far as to model the human voice box. When these experience problems, usually there will be a chirping sound in the audio; sometimes, voices will begin to sound strange, even robotic. However, because audio is so small compared to video, video problems usually manifest before audio problems.

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Setting Up Your System

Your video system should come with instructions on how to set up the physical hardware, and those instructions should be clearer and more precise for your exact model of endpoint than any instructions given here. The most we can do is give some advice on laying out your room:

  • Try to have the camera face away from windows. The bright sunlight will interfere with a good picture.
  • Try to keep a good distance between the microphones and the audio speakers. If you have directional microphones, point them toward the lecturer/participants, and away from the conferencing system's audio. This will reduce the chance of feedback and echo caused by the conferencing gear "hearing" itself.
  • Do not expect writing on whiteboards to show up on camera; the low contrast and high glare will almost always render it invisible. Expect instead to share content via computer images.
  • Try not to have your display monitors on camera; it is fine for testing but distracting for actual use.

You will also need to make some configuration settings on your endpoint. You may be asked to set these the very first time you turn the system on, or you may not. If you are using a Polycom system, they are all arranged under Admin Settings, in various subgroups. The following settings are arranged how most modern Polycoms organize them; older software or other makes may have these settings arranged differently, and some settings may not appear at all. (Settings not described below should generally be left at their default setting.)

  • General Settings
    • System Settings
      • System Name: Fill in something that allows both you and others to identify the precise location of your system; typically, identifying school, building, and/or room number are good.
      • Maximum Time in Call: 480. Setting this too low might cause your system to hang up in the middle of a class or meeting; setting it too high is generally only a problem if somebody accidentally leaving your video system connected outside of scheduled class times going to cause bandwidth problems.
      • Auto Answer Point to Point Video: Yes. Allows people to call your system directly easily.
    • Security Settings
      • Room Password: Set this to something that can be remembered. If you are having trouble, the IVN staff may ask you for this password to help them troubleshoot, so do not set it to something sensitive (like the root password to your database server or the password you use to get into your bank account.) Also, note that it is very easy to enter a number with the Polycom remote, and more difficult to enter a word or phrase; consider using a numeric password for your own ease of use. On newer Polycom systems, this password defaults to your system serial number.
      • Meeting Password: Leave this blank unless you want somebody to enter a password every time you make a call (which we strongly advise against.)
      • Use Room Password for Remote Access: Yes.
  • Network Settings
    • IP Network
      • Enable IP H.323: Yes.
      • H.323 Name: Can be the same as the System Name.
      • H.323 Extension: Often, the system will set one for itself; this will often work in a pinch (if it does not start with a 6, 7, 8, or 9). There may be a unified numbering scheme instituted in the near future; until then, we advise setting this to be the ip address of your unit (set below), expressed as a 12 digit number, with each number in the IP address making 3 digits, adding zeros to the front if necessary. For example, 131.118.5.236 would become "131118005236."
      • Use Gatekeeper: Specify.
      • Gatekeeper IP Address: 131.118.254.123
      • Quality of Service: Set "Type of Service" to "IP Precidence" and all the values (usually "Video," "Audio," and "Far End Camera Control") to "5."
      • Dynamic Bandwidth: No/Off.
    • Call Speeds:
      • Make sure at least 384 and 768 are selected. Select 1532 and 1920 if you have any interest in high-definition video.
    • Call Preference
      • Basic Mode: Off.
      • H.239: On.
      • IP H.323: On.
      • Preferred Speed: 768
      • Maximum Speed: Set this as high as possible without going over about a step or two below your available bandwidth (ie, if you are on a T1, which provides around 1500kbps, don't go over 1456 or so.)
  • LAN Properties
    • IP Address: Choose "Enter IP Address Manually" and enter the IP address, gateway, and subnet mask supplied by your netowrk administrator or the UMATS staff.
    • DNS Servers: Enter the ip address of your institution's DNS servers, or use the UMATS servers at 131.118.251.1 and 131.118.1.30
    • LAN Speed and Duplex Mode: Consult your network administrator. These can often be set to "Auto," but in some environments, this causes trouble; if you set these to Auto and experience a little visual disruption at a regular 10-second interval, try setting them to "100" and "Full" (or whatever was automatically negotiated on "Auto," which should appear on this page next to the settings.)
  • Global Services
    • Directory Servers: 131.118.254.123, with "ivn" as the password. Check the "Register" box.

Most of these settings can be set via the web page interface, which may be more comfortable for some users. The IVN staff will be more than happy to go through these settings with you, although at the very least the LAN Properties must be set correctly for them to access your endpoint and check it.

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Making Calls

Calling another endpoint or calling into a conference is almost as easy as making a phone call. There are a couple more rules and options than that, but for the vast majority of calls, just enter the number and the gatekeeper will handle the rest.

Dialing Into a Conference

Almost all conferences set up by the IVN staff have either a six digit conference code; some special purpose ones will have a five digit code instead. To call into a conference, just enter the code on your system, and that's it. As long as your endpoint is registered with the gatekeeper, everything should happen automatically.

If it is not registered with the gatekeeper, you will need to call the bridge directly. To do this, enter the ip address of the bridge. You will be given a welcome slide and asked for your conference ID. Dial it on the numeric keypad of your remote. If you have a Polycom system, note that most users must hit either the pound sign on the remote, or the "keyboard" button (if your remote has one), to tell the Polycom that you want to dial touch tones when you hit the numeric buttons on the keypad (otherwise, it thinks you are asking for camera presets).

Dialing Point-to-Point

For point to point calls, just like for a telephone call, one side needs to call and the other side needs to answer. The site being called doesn't need to do anything but answer, and we recommend that sites configure their unit to answer automatically so they do not even need to do that. The calling site will need one of the following peices of information to make the call:

  1. The other side's E164 address. This is just a number, just like a phone number or conference code, that uniquely identifies the other side.
  2. The other side's IP address. This is probably the most common method, and works even if the other side isn't registered with our gatekeeper or even on our network. Calls made to other institutions, or even other continents, are usually done by IP address.
  3. The other side's H.323 ID. This is a name given to the other side's endpoint by them, and usually relates to the location of the system. Entering these names manually is difficult because of the lack of structure in the name (a misplaced space or similar error can keep the call from going through) and the limitations of the remote control as a text-entry device. Fortunately, if your endpoint is connected to the global directory (which we recommend for Polycom systems and anything compatable), you can select "Directory" from your dialing screen and select the other side by name.

Note that dialing by IP address is currently the only way to call somebody who is not connected to our gatekeeper.

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Scheduling a Session

Most IVN sessions are scheduled. Keeping a central schedule helps track when rooms are available and allows the IVN staff to assign conference IDs and track resources on the bridges.

To schedule a session, click on "Schedule Video Session" or "Schedule Conference Call" on the menu to the left. (Both create conferences; the "Conference Call" just assumes all the participants are calling in over the phone and skips all the video-related questions. If you want a combined conference, with phone and video participants, schedule a video session.) Then, fill in the fields. Editing a conference you already created works pretty much the same way; go to the list of conferences, select one, hit the Edit button at the bottom of the page, and you will have the same options as listed here.

For conference calls, there are only two questions that need to be answered:

  1. Topic: A short description of the reason for your conference call. It should be short, but descriptive enough that your participants will recognize it if they look for it on the schedule.
  2. Callers: The total number of callers you expect. This should be the maximum number of people you expect to call in (to make sure enough ports are reserved) but no more (so you do not reserve ports you do not need and prevent somebody else from reserving a call of their own.

Video conferences are more complicated:

  1. Topic: Same as for a conference call: a short description of the reason for your conference call. It should be short, but descriptive enough that your participants will recognize it if they look for it on the schedule.
  2. Type: A general category for the event: class, administrative meeting, etc. Pick the most appropriate option from the list.
  3. Home Room: The location that is hosting the session. If it is a class, for example, this will be the location where the professor is. (You will need to add rooms, as described below, before you can select this.)
  4. External Sites: A count of how many non-IVN locations will be joining the call over the Internet. Usually, this will be zero.
  5. Voice Callers: A count of how many people will be calling in from a telephone instead of from a video endpoint. Usually, this will be zero.
  6. Video Callers: A count of how many sites will be calling in over ISDN. This will almost always be zero.
  7. Point to Point: If there are only two endpoints in the call, this option will be available; setting it to "Yes" indicates that one site will call the other, and no bridge space needs to be reserved. This is recommended for both the quality of the video call and for saving video ports.
  8. Conference Bridge: The conference bridge ID assigned to your conference. This will be the number participants will dial into. It may be blank if there isn't enough information to assign an ID (ie, there are no times or rooms selected) or if the conference has been marked Point to Point.
  9. Dial-in Number: If your conference has voice callers or ISDN participants, this is the number they will call to connect on. Generally, they will call this number, be prompted to enter their conference ID followed by the pound sign, enter the Conference Bridge number, and be connected to your conference.
  10. Profile: The profile to use on the bridge. See the description next to the selection box for more information. Selecting "Single384" or "Single768" will put your call on the old bridge, which you probably do not want. When in doubt, select "CPAutoPresent" for meetings, and either "CPAutoPresent" or "Single" for classes. ("CPAutoPresent" shows all the sites when there's discussion, but only the site that's talking when somebody is presenting/lecturing; "Single" only shows the site that's talking or talked last at all times.) For more information, see the information below the profile setting.
  11. Add/Edit Rooms: Click this button to select the rooms that will participate in your conference. Rooms are organized by site, so if, for example, you want to add Towson's Cook Library conference room, find Towson's box, and the Cook Library room will be there. Some sites have more rooms than will fit in the box, so if you don't see the room you want, remember to scroll down. Hit Save Changes when you are done.
  12. Add/Edit Session Times: Click this button to schedule times for your conference. There are several ways of entering times; select the way you want to enter information by selecting the box/circle next to it on the left.
    There is a calendar at the top of the screen; any time you are entering a date, you can select the box where the date goes, then select a date from the calendar and it will fill it in.
    There are also two ways to enter the length of the session: either as a duration (as in "this session lasts one hour") or by end time ("this session ends at 2:30"). Just select which one you want from the drop down box. Also note that you can enter times either with "am" or "pm" (as in "1:00pm") or in 24 hour time (as in "13:00").
    When entering conference information, you can only enter one start and end time, even if you're scheduling multiple sessions; if you need different start times (for example, 1pm on Tuesdays and 3pm on Wednesdays) you need to enter them one at a time. There's no limit on the number of different start and end times a conference can have, though.
    • Add a single session: Enter a single date and time for your conference.
    • Add several sessions: Just like adding a single session, except that you can enter more than one date.
    • Add recurring sessions: If your session happens on a regular weekly basis (for example, if it is a regularly scheduled class or meeting), you can enter its information here. Select the day or days your session meets, the start date and end date, and the time information. Teh start and end date do not need to be exact; for example, if your session meets on Tuesdays and Thursdays for a whole semester, you can enter the start and end date of the semester here, and not worry about when the first Tuesday and last Thursday fall.
    • Remove recurring sessions: If your sessions have a recurring pattern, and you need to remove some of them, select the pattern here. You can hold down the Control (CTRL) key to select more than one. For example, if you have scheduled your sessions for Mondays, Wednesdays, and Fridays, and need to cancel just the Fridays, you can select it here. Also note that the system doesn't just remember what you added, but actually looks for patterns, so if you enter every Tuesday for a month by hand, it will show up on the list here.
    • Remove specific sessions: To delete specific scheduled sessions, select them here.
    • Finished: Click this button to add/remove whatever sessions you have selected and return to the conference settings page. Note that, when editing a conference (as opposed to creating a new one), these changes happen immediately, and will stick even if you hit Cancel on the Conference Settings page.
    • Apply and Continue: Click this button to save your changes and enter more changes.
    • Cancel: Cancel the current changes and return to the conference settings page. Any changes already applied will not be cancelled.
  13. Save Changes to save your conference settings, or Cancel to change your mind and forget about this conference.

Conferences can have any combination of dates and times; if you need to have the same people meet for the same purpose on multiple occasions, adding dates and times to an existing conference is recommended over creating new conferences.

See also: Tips on Using the IVN Web Page.

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Tips on Using IVN

Preparing for a Conference

  • If you are connecting with an outside location, over a non-standard setup, have a lot riding on this call working properly, or have any doubts at all whether everything is going to work properly, test beforehand. The IVN staff feels safer when things are tested beforehand, too; contact us if you want our assistance with testing. Try to test far enough in advance that any trouble can be worked out in the interim; more time is better, especially when the other side of the call is 8 or more hours off of local time and arranging a time when both sides can test and experiment can present a challenge.
  • If the conference is bridged, try to call in a few minutes early. Everybody feels more confident that everyone will be present if everybody is there early.
  • Avoid having bright light shining into the camera. The camera will adjust to the bright light and make everything dark. Windows with daylight shining through are very common and cause all sorts of trouble.
  • If you have pictures to share with the other participants, try to set them up on a computer as PowerPoint® sides or something similar, rather than drawing them on a chalkboard or whiteboard during the conference. Whiteboards and chalkboards are hard to see at best, and often totally unreadable, on camera.
  • Presenters should wear solid colors. Avoid wearing stripes, as some cameras will have trouble with them, resulting in an interesting but ultimately distracting "moire" effect.

While In a Conference

  • When speaking, speak as clearly as possible. If your microphone is stationary (as opposed to one pinned to your shirt, for example), be sure to speak in its direction.
  • Remember that your camera represents some number of fellow conference participants and/or students, and talk to it from time to time.
  • Remember that videoconferencing can add a noticable delay between when one person speaks and when they are heard, similar to when people are speaking over a satellite link. Also remember that it may be harder for them to interrupt to ask a question or make a comment than it would be if they were in the same room. Try to pause for questions and comments, and wait longer than normal for a response. (Five seconds is usually sufficient.)
  • When not speaking, consider muting your microphones. The remote for your endpoint should have a mute button, and many microphones have a mute button as well. This will help reduce the noise on the conference and make everything sound clearer to everyone.
  • If your microphones ae not muted, be aware that they are very, very good at picking up sounds that vibrate whatever they are on or blow air in their direction. Things like shuffled papers, coughing toward the microphone, and tapping on the table the microphone is on become very, very loud in a teleconference. If you cannot mute your microphones, be aware of these sorts of noises.
  • If there is an echo in the conference, try muting sites one at a time until the echo goes away. The last site to mute is causing at least some part of the echo; they should adjust their volume, if possible, or remain muted when not speaking.
  • If you are disconnected mid-conference for some reason, try to dial back in; most disconnects are caused by minor transient problems, accidents, or by an endpoint's "maximum time in call" setting being exceeded.
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Tips on Using the IVN Web Page
  • When editing settings, there is usually help available nearby to explain what you are seeing. Some of the help changes based on what you select, to explain it more clearly; often, the help will not change until you actually click on a change, as opposed to when you're in the picking process, so pick what you want to know about and the help text should provide some additional information.
  • When selecting a profile for a conference, if you are unsure what to pick, take a look at the section below the profile setting, where it says "The profile determines several important features of your conference, including:" Most the information you need is there. If you're still unsure, call or email us and ask.
  • Changing the home room or profile for a conference will almost certainly cause the conference ID to change. Avoid changing these, especially very close to the conference time.
  • Changing other conference settings may still cause the conference brige number to change, mainly because the bridge it was originally assigned to does not have the resources to carry the conference. Specifically, adding participants is more likely to cause a bridge change than removing them.
  • The IVN staff may be able to arrange things even if the web page says they are impossible, so it does not hurt to ask in an emergency.
  • Remember that, when you request a conference, all the participants must approve it for it to be finalized.
  • When viewing a list of classes, click on the ID to view conference information. If the conference is awaiting your approval, a button allowing you to approve or reject it will appear by your room in the Rooms list. If you have permission to edit the conference, there will be a button at the bottom of the Conference Information page to do so.
  • Clicking on the Conference Bridge number in a list of conferences will show a list of all conferences on that bridge number. (Bridge Number and Conference ID are the same thing.)
  • On the Calendar view, if you click on a session, it will take you to the conference information for that session. If you click on a time block with multiple sessions, it will show you that time block, so you can select which sessions you wish to see.
  • If you are an administrative contact for more than one location and select "Approve" from the list of conferences awaiting approval, then it will mark the conference approved for all the sites you are administrative contact for. If for some reason you only want to approve some of those sites, click on the conference ID, and approve the sites individually.
  • If there is an old conference you want to schedule a new session for, and you aren't sure how to search for it, "My Conferences" is the easiest way to look.
  • When searching the conference schedule, not that the start time says "from the start of" and the end time says "through the end of." These are meant literally; if you select "today" for the start time, it starts searching at 12AM this morning, and if you select "today" for the end time, it stops at 11:59:59 tonight.
  • The semesters on the search page are inexact, and semesters are not currently an option for scheduling; this is because different schools have different semesters, and the term has become confusing and misleading.
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Frequently Asked Questions

What do all these videoconferencing terms mean?

Here are some definitions for some of the terms we use:

Bridge: A device that many endpoints can use to have their calls combined, or "bridged," into one. Without a bridge, each endpoint could only talk to one other system at a time. (Some endpoints can call more than one other site at a time; these endpoints have bridges built in.) Usually, these different conferences are identified with a conference ID, or "bridge number," that is entered on the when calling in.

Conference: A generic name for any teleconferencing session, whether it is a class, a meeting, a symposium, or anything else.

Conference ID: A numeric code that identifies a conference. Conference IDs may be dialed by endpoints, or they may be entered after connecting to a bridge.

Continuous Presence: A format for conferences with more than two participants. With only two participants, the logical arrangement is for each site to see the other; however, when there are more than two sites, things become more complicated. One common solution is to show the site that is speaking (or generally making the most noise.) Another is to show all the other sites at once, each in a different part of the screen, so that each site can see what is happening at all the others. This is called "continuous presence," because all the sites are always there.

E164 Address: A number assigned to an endpoint or a conference bridge. All "E164" means is that, if any part of the number means anything interesting, the interesting parts go on the left. For example, on the IVN system, an E164 address that starts with "60" is a voice conference, while one that starts with "80" is on the bridge called "IVN-RMX-A".

Endpoint: A teleconferencing device that lets users make video calls. It usually has, or connects to, a camera and monitor to share video, and speakers and microphones to share audio. It may also connect to computers, projectors, VCRs, and other equipment to share documents, recordings, etc. Most IVN sites use Polycom endpoints, and so many users call their endpoint "the Polycom." (A few sites use other equipment, like Tandberg or Lifesize.

Gatekeeper: The computerized operator of the video network. The gatekeeper keeps a directory of endpoints, directs calls, and can even decide whether endpoints are allowed to call each other. The IVN gatekeeper has a very open policy, allowing endpoints to call in and out freely.

H323 ID: A name given to an endpoint. H323 IDs can be almost anything, but they must be unique and should be useful in identifying the system, as they are published in the directory and used by IVN staff to locate your system for troubleshooting. Good names might include institution name, campus, building, and/or room number (like "TU/Burdick_102" or "CSM LaPlata"), or for a desktop system, your name. Arbitrary or unhelpful names, like "Fred the Polycom" or "System 3" are technically valid, but are not intutitively helpful.

IP Address: A number that represents a network location on the network. While things like firewalls can make the situation very complicated, the original idea was that every single computer on the Internet has a single IP address. IP addresses are written as four numbers, each between 0 and 255, separated by periods (or "dots"). For example, an endpoint might be assigned the IP address of "131.118.5.236".

Hollywood Squares: A nickname for Continuous Presence, because each site appears in a box, like the celebrities on the famous game show.

Point to Point: A call that doesn't go through a bridge. Point to point calling may be used in conferences with only two participants; doing so saves resources on the bridge and may give better performance in the conference.

Polycom: A company that makes videoconferencing equipment, like bridges and endpoints.

Presentation Mode: A setting on the bridge that tells it to switch between continuous presence and a full-screen display of a single site when that site has been the only one talking for a certain amount of time. The result is that, when one site is doing all the talking, as when a particular person is "presenting" material (hence the name), they have everybody's full attention. When somebody else starts talking, the display switches back to continuous presence, allowing for discussion, until somebody else is doing all the talking; then they become the "presenter" and everybody else sees them. (The "presenter" sees all the other sites while they are talking.) This feature often sounds confusing when described, but the end effect is actually very natural: the screen almost always displays exactly what you want to see.

Profile: A set of settings for a conference. Conferences can have a lot of settings, likr what speed to connect at, or whether or not to show all the participants at once in little boxes, or just whoever's talking, or to switch back and forth (as in presentation mode.) All of those settings are put into a profile, and then the profile is assigned to conferences, instead of each setting being assigned separately.
Because of the way profiles are attached to conference IDs, changing the profile of a conference will often require a new conference ID.

Transcoding: Different endpoints have different capabilities; some may be able to support higher or lower resolution video, or faster or slower speeds. Sometimes these differences are negotiated, worked out by the different endpoints so that they can agree on what they will send and receive (usually the lowest common denominator.) Transcoding refers to the ability (usually of a bridge) to accept connections at different speeds, resolutions, etc, and translate between them, so that each endpoint can send and receive what it can do the best with, and so that one old, slow, or strange system does not force all callers to drop to a lower quality to accomodate it.

We may use multiple terms for the same thing. For example, in most contexts, "session," "class," "meeting," and "conference" all mean the same thing, as do "conference ID," "bridge number," and "meeting room ID." Occasionally, they have different shades of meaning; for example, sometimes a "session" means one occurance of a recurring class or conference. If you're not sure what we're talking about, please ask.

Back to the list of frequently asked questions

What are the "old" bridge and the "new" bridge? Which one should I be using?

The "old" bridge, also known as the "Cisco" or "Radvision" bridge, has been in service since IVN moved to IP video in 2000. It can support both voice and video calls, but it has some limitations. For example, it cannot support continuous presence or transcoding; all calls show the last speaker, and all callers have to connect at a predefined speed or they will not receive video at all. The "new" bridge, the Polycom RMX, supports these features and more. As much as possible is being moved to the new bridge to take advantage of these features, but the old bridge is still active to support any legacy setups that do not work well with the new bridge, as well as to support voice-only conferences.

As a rule, users should be using the new bridge. It is possible to request the old bridge, by choosing one of the old bridge profiles: the ones that do not support transcoding. Unless otherwise advised by the IVN staff, there is probably no good reason to pick these, and they may be removed as options at any time.

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Can I call into a conference from my desktop/laptop?

Yes, this is possible; however, registering your desktop software with the gatekeeper takes up resources there, as does calling into the bridge. If too many resources get used up, endpoints will be unable to connect to their conferences. Because of this, we ask users not to register a lot of desktop systems as endpoints, not to register or call in lightly, and not to experiment too much. This policy may change if resources become too strained.

Another problem with desktop users is that they are often calling in from home. These connections occur over the open Internet, where video traffic may be delayed or dropped according to those providers' network policies and limitations. (IVN performance is a goal of the UMATS network, so we handle video traffic with care and speed; other networks have no reason to do so.) Also, home users are often behind home firewalls and/or NAT boxes, which will interfere with video traffic or block it completely.

As with most things, the UMATS staff asks that you work with us if you want to connect from your home or work computer.

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What's with the delay? Why does it take so long for the other side to see/hear what I say?

The short answer is that it takes time for all of the systems in place to take the sound and the picture, turn them into data, send them over the network, and have the other side decode them back into pictures and sound. The delay can be helped to some extent by adjusting the call settings, and calling point to point instead of going through the bridge can help a little, but for now, at least, the delay is a fact of life for videoconferencing.

For the more technically curious, here is a little more detail on the delay. When an endpoint sends audio or video, it needs to stuff that data into packets. Often these packets will contain 20-100 milliseconds (ms) of audio or video. (Usually the video is longer, and the far side must wait for whichever takes longer, since the audio and video are synchronized) This is your first source of delay; the microphones and camera have to record 50ms of information before it can send anything. If the bridge is being used, this delay becomes larger, as the bridge decodes all the audio and video, mixes them together, and resends it. Another minor source of delay is the network itself; it takes time for data to cross all the network connections between you and the other side. This is a much larger problem in interstate or especially international calls than it is across the IVN network.

A third source of delay comes from what is called "jitter." Because the network is shared, traffic does not arrive evenly. The sender might send three packets at 50ms intervals, and the second one might be delayed 25ms longer than expected, so that, instead of 3 packets at 50ms intervals, the receiver sees the second one 75ms after the first, and the third 25ms after the second. If the packets were played just as they were received, the video and audio would become very choppy and irritating. So the endpoints use what is called a "jitter buffer" to hold a little bit of video and audio in reserve. The effect is a lot like watching Internet video; when you first request a movie, usually you will see a message that it is "buffering" the video. Then, when the video starts, you may notice the download pausing and restarting, but what you watch is smooth because you (in theory) don't catch up to where the data is arriving in bursts.

So, for a point to point conneciton, if you have 50ms of delay on sending your video to collect a full picture, plus 5ms of transit time 25ms of jitter buffer, you can expect the other side to see and hear you a little under a tenth of a second. If you're using 100ms video frames and going through the bridge, as is common for most classes, you will see 100ms to send, plus 25ms of jitter buffer on the bridge, plus 100ms for the bridge to re-send, plus 25ms of jitter buffer on the receive side, it will be a quarter second before you are seen and heard at the remote site, and a quarter second more before any response is heard; hence, the common half second pause between when one location finishes talking and another responding.

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Where is that echo coming from?

Echoing is a common problem for videoconference calls. The bad news is that it can be very distracting. The good news is, you are getting that instead of feedback. And the problem can be fixed.

What is happening is very straightforward: The microphones at some location are picking up what is coming from the speakers, and rebroadcasting it. This gets worse if more than one site has the same problem; person at site A speaks, site B echos it back to A, site A echoes it back to B, and so in. It can echo several times before fading out, or, worst case, one or more end systems might try to "helpfully" amplify it (assuming it is quiet because the speaker is not speaking loud enough or is too far from a microphone), causing it to continue indefinitely. Most endpoints have echo-cancellation capabilities, where they can, in theory, detect an echo and remove it, but they are not always successful, especially if the echo starts out very loud.

The solution is simple enough: Stop the microphones from picking up the audio, or at least from picking it up so loudly. One way is with distance; the farther the microphone is from the audiospeaker, the less likely it is to echo. Other methods include turning down the volume on the endpoint and pointing directional microphones away from the speakers.

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I want my own site to appear on screen with the other ones; is this possible?

Yes. Your end system can be configured to display your local video on one monitor if you have two and nobody is sharing content. Even with one monitor, you can make your local video appear in the picture-in-picture (PiP) window. If you want your screen to appear exactly like all the other sites on the screen, that is possible, too. Select a profile with "Same Layout" option (help text will say, "your own site visible.") This sends the exact same picture, showing all the sites at once, to all the sites, instead of making an image for each site that has all the other sites except themselves on it. This layout makes some other features unavailable, like Presentation Mode, where the display switches to the person who is talking, and changing your own layout.

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I don't like how the screen is laid out. Can you or I change it?

Yes. If you are in a conference that supports it (ie, you are not on the old bridge or using the Same Layout option to see yourself), you can use the dial pad to enter the asterisk twice ("* *"), and the bridge will display a list of layouts on your screen. Press the number that goes with the layout you want, and it will switch. (Note for Polycom users: you may need to press the pound sign on the remote to switch the keypad from selecting camera presets to acting as a dialpad for touch tones. If, when you hit numbers, either nothing happens or the camera suddenly moves to point somewhere else, this is the most likely problem.)

If you want the layout changed for everyone, call us. If you want the change to be permanent, then a profile change will be necessary.

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Getting Help

If you are having a problem using the system, there may or may not be somebody at your site who can help. If there isn't, or if the problem is not something they can help with because it isn't local to you, you can always call the IVN staff. They can be reached as a group on the UMATS NOC line: (301) 445-2764. If nobody answers, leave a message and the voice mail system will page us with your problem. You can also feel free to call individual members of the staff if you are more comfortable doing so, but if you leave a message, the voice mail system will not page them, so if nobody answers, try the NOC line.

For less pressing matters, email noc@usmd.edu. We generally try to answer email as soon as possible; although it isn't guaranteed, you will often get a response immediately, or at least within the hour, during business hours, and will rarely have to wait longer than the next business day.

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