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Video Conferencing Defined, Part 3
February 10, 2009 @ 04:00 AM | By Brian Trampler & Sara O'Rourke

2009-02-10-VideoConferencin The Technical Side of Video Conferencing

Now that you know about the types and features of video conferencing, let’s talk about the technology behind a video conference.

Step-by-step problem-solving procedure. Transmission of compressed video over a communications network requires sophisticated compression algorithms. Some video conferencing systems offer both proprietary and standard compression algorithms.

Aspect ratio
Ratio of a picture’s width to height. In video, this ratio is four units wide by three units high or 4:3.

Analog signals
Audio/video signals currently used in broadcasting where the signal is represented by variable measurable physical quantities (such as voltage). Current TV and radio signals are analog, as are many telephone lines (contrast with digital.)

In casual use, the amount of information that can be transmitted in an information channel. High bandwidth Internet access means web graphics load quickly in your browser window. High bandwidth video conferencing means that the picture and sound will be clear. In computers, bandwidth refers to the speed at which data can be transmitted on a communications frequency. In telecommunications, the maximum frequency (spectrum) measured in Hertz or cycles per second, between the two limiting frequencies of a channel.

Bit (binary digit)
Smallest unit of information; two possible states. Examples include:
One or zero
Yes or no
On or off

Bits per second (lower case is significant).

Bps or BPS
(8-bit) bytes per second (upper case is significant).

High-capacity communications circuit/path. It usually implies a speed greater than 1.544Mbps (in contrast with wideband and narrowband).

BRI (Basic Rate Interface, ISDN)
Three digital signals over a single pair of copper wires: two voice (B) channels and one signal (D) channel (e.g., voice and fax on a single pair of wires).

Compressed video
When the vast amount of information in a normal television transmission is squeezed into a fraction of its former bandwidth by a codec, the resulting compressed video can be transmitted more economically over a smaller carrier. Some information is sacrificed in the process, which may result in diminished picture and sound quality.

Measurement for bandwidth in bits per second. In general, the higher the datarate, the higher the quality of video.

Digital signals
Audio/video signals represented by discrete variations (in voltage, frequency, amplitude, location, etc.). A digital clock, for example, displays the time as discrete numeric values rather than angular displacement of analog hands. In general, digital signals can be transmitted faster and more accurately than analog signals. As an example, music from digital compact discs is usually clearer than music from analog records (contrast with analog signals).

Standards-based formats for communicating between video conferencing systems from different vendors. QCIF is one quarter of the resolution of FCIF.

Frame rate
Frequency in which video frames are displayed on a monitor, typically described in frames-per second (fps). Higher frame rates improve the appearance of video motion. Broadcast TV (full motion video) is 30 frames-per-second.

Full duplex audio
Two-way audio simultaneously transmitted and received without any interference or "clipping." A common feature of room-based video conferencing systems (contrast with half duplex audio). Full motion video is equivalent to broadcast television video with a frame rate of 30 fps. Images are sent in real time and motion is continuous.

Half duplex audio
Two-way audio transmitted and received in turn (rather than simultaneously) so only one site can speak at a time (contrast with full duplex audio).

KBPS (Kilobits per second)
Method of measuring the speed of transmission. The higher the KBPS or speed, the better the quality of the video conference.

Low-capacity communications circuit/path. It usually implies a speed of 56Kbps or less (contrast with wideband and broadband).

Standard for scanning television signals. Used in the U.S., Canada and Japan.

Standard for scanning television signals. Used in most European countries.

Proprietary compression algorithm
Vendor-specific algorithm for compression of a video signal. A video conferencing system using a proprietary algorithm can only communicate with a remote site using the same algorithm. Many vendors also adhere to standard compression algorithms to facilitate communication across platforms.

Defines the type of system the client is utilizing, including:
Continuous presence

Rate (and ultimately the number of lines) a conference uses. The more lines, the higher the speed and better picture quality. Speed runs in increments of 56kbps or 64kbps. Examples include:
112: 2X56kbps
128: 2X64kbps
224: 4X56kbps
256: 4X64kbps
336: 6X56kbps
384: 6X64kbps

Standard compression algorithm
Algorithm convention for compression of a video signal. Adherence to standards allows communication among a wide variety of video conferencing systems, though not with the same clarity as two similar systems using a proprietary algorithm. H.320 is the most widely accepted standard in use today.

Medium-capacity communications circuit/path. It usually implies a speed from 64Kbps to 1.544Mbps (contrast with broadband and narrowband).

After this three part series in video conferencing definitions, I hope that you can walk away with some clear knowledge on what it means to have a video conference. Please remember that these are just some of the words you may hear when talking with other people in the industry. To learn more about InterCall’s video conferencing click here.

Brian_2 Brian Trampler is the Sr. Product Manager of Strategic Video Solutions & the "Video Conferencing" blogger. Throughout his 10 years in the conferencing industry, he has successfully launched numerous web, streaming, and video services.  Prior to making the jump to conferencing, Brian was involved in gymnastics both as a competitor and coach.  If you’re lucky, you might also find Brian performing musical theatre throughout the Denver metro area.

Sara_2 Sara O'Rourke is the Associate Product Manager for Strategic Video Solutions and will be a contributor to "Video News". She has been with Intercall for over 4 years and has specialized in the video product for the majority of those years, starting in sales. She is not only an accomplished professional of the video industry, but a fine singer as well.

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