Video Conferencing Overview
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What is video conferencing?
Video conferencing is two-way interactive communication delivered using telephone or Internet technologies that allows people at different location to come together for a meeting. The video conference can be as simple as a conversation between two people in private offices (point-to-point) or involve several sites (multi-point) with more than one person in large rooms at different sites.
A basic video conference setup has a camera and a microphone. Video from the camera and audio from the microphone is converted into a digital format and transmitted to a receiving location using a coding and decoding device, often referred to as a "codec".
At that receiving location is another codec device that decodes the receiving digital stream into a form that can be seen and heard on monitors or televisions. At the same time, video and audio from cameras and microphones at the received location is sent back to the original location. |
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What are the benefits of video conferencing?
Video conferencing saves travel time and money. Participants can see and hear all other participants and communicate both verbally and visually, creating a face-to-face experience. PowerPoint and other on screen graphic, as well as other cameras are also available presentation options. People downtime is reduced and productivity gains are achieved by removing the logistics of flight preparations, airport delays, hotel stays, and all the other inconveniences of business travel. In distance education, video conferencing provides quality access to students who could not travel to or could afford to relocate to a traditional campus. Video conferences can also be recorded and made available in a variety of ways, e.g., DVDs, streaming video. Besides distance education, other applications include meetings, dissertation and thesis defenses, telemedical procedures, and online conferences.
People use video conferencing when:
- a live conversation is needed;
- visual information is an important component of the conversation;
- the parties of the conversation can't physically come to the same location;
- the expense or time of travel is a consideration.
Examples of how video conferencing can benefit people around campus:
- Guest lecturer invited into a class from another institution.
- Researcher collaborates with colleagues at other institutions on a regular basis.
- Thesis defense at another institution.
- Administrators from different parts of campus need to collaborate on adminstrator issues such as a campus strategic plan.
- Researcher needs to meet with a review committee about a grant.
- Student interviews with an employer in another city.
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Please explain the appropriate etiquette when video conferencing.
- Allow a few minutes for setting up and shutting down the videoconference.
- Stick to time limits.
- Remember to mute your microphone when you are not talking.
- Consider using a location banner.
- Take turns speaking and allow time for audio delay.
- Don't multi-task on camera.
- Be aware of possible audio distractions if your microphone is not muted - coughing, paper shuffling, air conditioning units, laptop and projector fans, phone ringing, etc.
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What environmental issues need to be considered?
- Clothing: Solid colors are best. Busy outfits blur when on camera. Simpler patterns aid the video compression.
- Lighting: Think "TV studio lighting". Soft white frontal light is preferred. Standard overhead lights can cast shadows. Camera can not focus properly in low light.
- Back drop:
- No hard lines or complicated patterns.
- Can use a dry erase board, but be aware of glare.
- Solid darker color is ideal.
- Avoid red backgrounds they can be hard on the viewing site.
- Give audience one thing to focus on—YOU.
- Good idea—use a sign to indicate your location
- Audio setup:
- Keep the microphone away from where the speakers are located. This can cause audio loop back.
- Test audio levels ahead of time. Make a test call. Use built-in features of the video conferencing system to test.
- Make sure microphones are away from extraneous noise generators: Air conditioners, laptop/projector fans.
- May need to add echo canceling hardware. This is less common as conferencing systems are becoming better at handling audio.
- Large conference room considerations:
- Position the camera to see the primary speaker and audience.
- May want to add additional cameras.
- Consider investing in good lighting.
- In especially large rooms, designate locations for Q&A with microphones.
- Avoid panning the camera too much. Use endpoint “presets
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What are some tips for a successful videoconference?
Provide an overview for new users to learn basics:
- Share rules of etiquette.
- Get experience using the remote control (room based systems) or using the desktop client software.
- Emphasize the importance of muting the microphone when you are not speaking.
- Test with each location prior to the video conference. Testing provides experience and creates a positive experience.
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What enables a quality videoconference?
The quality of a video conference primarily depends on the characteristics of the network connection between the conferencing sites. In the H.323 world, a high-quality conference (excellent audio and video) needs about 768 kbps (kilobits/second) of bandwidth on a switched network. On campus, this is possible since most network connections are 100 Mbps (megabits/second).
When a video conference includes an off-campus site then the type of network connection, the bandwidth between sites, and firewalls must be considered.
General rules for bandwidth:
| bandwidth |
network |
expected quality |
| 768 Kbs |
Internet2, on campus |
Excellent |
| 384 Kbs |
commodity Internet, ISDN |
maximum good connection across the commodity Internet or through an ISDN connection |
| 256 Kbs |
commodity Internet
Use only if 384 Kbps not possible |
Audio okay, video barely full motion |
| 128 Kbs |
commodity Internet
Use only if 256 Kbps is unavailable |
audio marginal; chopping video |
Internet2 is the next-generation Internet which is in use at virtually all R1 research universities and some business and government sites.
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Can I video conference from home? my office? a hotel?
Technically, the answer is yes. A USB camera, a microphone, and video conferencing software can turn your computer into a video conferencing system. See "Hardware and Software Videoconferencing Solutions" for H.323 videoconferencing recommendations for computers. Coming soon...
In actual practice, however, it can be difficult to accomplish. The main stumbling blocks are adequate bandwidth and firewalls. |
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Please explain the different video conferencing standards.
Several standards for video conferencing have been developed. The three most popular standards are:
- H.320, used for ISDN (Integrated Switched Digital Networks) or digital telephone lines; developed by the International Telecommunications Union.
- H.323, used for IP (Internet Protocol) conferences; allows for video conferences over the Internet; also developed by the International Telecommunications Union
- SIP (Session Intiation Protocol) is a signaling protocol developed by the IETF Multiparty Multimedia Session Control working group. Areas for use of the protocol includes but are not limited to telephony, presence, video, instant messaging, online games and events notification in general.
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ISDN or IP?
If you have a choice of having an ISDN versus an IP connection with the off-campus site, you have two issues to consider: quality and cost. There will be additional charges (for you or the site you are connecting to) for ISDN. In general, there are no additional charges for IP (based on the current funding model for data connections on campus). You will get consistent quality with an ISDN connection. Over the commodity Internet you do not have guaranteed bandwidth which implies you will not have guaranteed quality. Conferencing over Internet2 implies high quality.
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What is a video conferencing bridge?
A video conferencing bridge (also called a Multipoint Control Uni or MCU) is a hardware system that is able to connect multiple videoconferencing systems together into a single conference.
A video conferencing bridge receives digital video and audio signals from codecs in a designated conference, processes and resends digital video and audio signals back to all the codecs. Multiple conferences involving many locations can be conducted simultaneously. Many bridges can provide advanced features such as continuous presence, people plus content or dual streams, transcoding, and transrating. |
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What is continuous presence?
Continuous Presence is a feature available during video conferences that allows all participants to be visible on the screen at the same time. For instance, if there are 12 participants in the video conference, the screen everyone sees will have 12 windows (which can be of various client defined sizes) with each participant in their own window.
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What is people plus content, or dual stream?
People plus content is a standard (ITU H.239) that allows a video conferencing system to process high resolution VGA graphics along with the standard video signal. This means video conferencing system in the conference sends and receives two video stream - video and VGA graphics. Example: In a classroom equipped with two monitors, the students could see both the instructor and the presentation on the two different displays.
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What is transrating?
Transrating is a function available on the video conferencing bridge that allows conferences among site and locations with different bandwidths. For instance, transrating allows virtual classrooms with Internet2 connections participating at 2 Mbps while another locations with limited bandwidth can participating at a lower 384 Kbps rate.
What is transcoding?
Transcoding is an option available on video conferencing bridges that allows conferences to be established with participants using different video conferencing formats. For instance systems and location using ISDN (H.320) can seamlessly communicate with other locations using IP or Internet connections (H.323).
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Please provide an overview of H.323 video conferencing.
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The H.323 standard specifies the components, protocols, and procedures for the transmission of real-time audio, video, and data communications over IP (packet-based) networks.
Point to point video conferencing: In its simplest form H.323 video conferencing consists of two H.323 video conferencing sysrtems talking to each other over the Internet. This is called "point to point" conferencing. One station initiates the call, and the other either accepts or rejects it. Once accepted, encoded and compressed audio and video flow between the two stations.
Multipoint video conferencing The last major piece in the puzzle was to provide a means for multipoint video conferencing, i.e., more than two sites. In the H.320/ISDN world, a Multipoint Control Unit (MCU) was used. This allowed three or more user stations to connect to the MCU. In a "voice switching" mode, the MCU made a decision about which site was currently talking (or talking the loudest). The MCU then transmitted the audio and video stream for the selected terminal back to all other terminals. As users at a different terminal started to talk, that terminal’s audio and video signals were sent to all other terminals.
The H.323 world adopted this same method of providing multipoint operation. H.323 MCU's are far less expensive. They require only a single network connection rather than multiple ISDN lines.
There are four components to H.323:
- Terminal/Endpoint/Conferencing System/Codec: A basic video conference system has a camera and a microphone. Video from the camera and audio from the microphone is converted into a digital format and transmitted to a receiving location using a coding and decoding device, often referred to as a "codec".
- Multipoint Control Unit (MCUs): Supports conferences between three or more endpoints
- Gateway: An optional element, gateways provide translation functions between H.323 conferencing codecs and other conferencing terminals, i.e., H.320.
- Gatekeeper: Performs two call control functions - address translation from aliases to IP addresses and bandwidth management. The collection of all terminals, gateways, and MCUs are managed by a single gatekeeper is called an H.323 Zone.
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What is a firewall? How does it affect H.323 video conferencing?
A firewall protects your network from unwanted Internet traffic. A firewall can be an appliance installed on the network or software running on your computer. When installed, a firewall exists between your computer(s) and the Internet, i.e., a virtual wall. The firewall lets you request web pages, download files, chat, etc. while making sure other people on the Internet can not access services on your computer like file or print sharing.
If a videoconferencing system (any type) is behind a firewall, it cannot receive communications from H.323 gatekeeper, so it cannot complete a registration or use gatekeeper services. (The gatekeeper is not a means of bypassing the restrictions of a firewall.) A videoconferencing system behind a firewall must initiate a videoconference using the IP address of the remote video conferencing system since it cannot make use of the gatekeeper's services. Firewalls maks it difficult to use videoconferencing bridge for multipoint videoconferencing.
There can be a series of firewalls to address:
- Does the institution you are at have a campus firewall? Currently, the University of Iowa does not have a campus firewall.
- If you are running Windows XP, is its firewall turned on?
- If you have computer protection software installed such as Symantec's Nortion Utilities, is its firewall turned on?
If a firewall is required, an external or software firewall with the ability to open specific ports for H.323 "traffic" is recommended. The following ports must be opened in the firewall and assigned to the videoconferencing endpoint(s):
- Port 389 (TCP): For ILS registration
- Port 1503 (TCP): Microsoft NetMeeting T.120 data sharing
- Port 1718 (UDP): Gatekeeper discovery
- Port 1719 (UDP): Gatekeeper RAS (Must be bi-directional)
- Port 1720 (TCP) H.323 Call setup (Must be bi-directional)
- Port 1731 (TCP): Audio call control (Must be bi-directional)
- Ports 3230-3235 (TCP/UDP): Signaling and control for audio, call, video and data/FECC
- Port 3603 (TCP): Polycom ViaVideo Web interface (Polycom ViaVideo users only)
More information on firewalls is available at the University of Wisconsin Extension’s website, “Firewall Reference”.
http://www.uwex.edu/ics/support/video/H323/firewalls/reference.html
Other firewall references:
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References:
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