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How Does Video Conferencing Work?

Describing a Video Conference can be as basic as an IP address -to-IP address connection and as complex as fully-immersive Telepresence with a musical score, a full data presentation, and full-heighted conference participants. It is somewhere in the middle that most Video Conferences fall, and so this is the imagery I will use.


It is incredibly important to note that there is no complicated call initiation with Video Conferencing systems because they are ever-on, unless you turn them off. Like a voice-only telephone, Video Conferencing systems are perpetually available for incoming and outgoing video calls. You can choose to set your system to auto-answer incoming calls or to manually accept incoming calls.

Connecting Interface

If you are using a desktop-based system – such as with the Polycom m100, or a monitor-based system – such as with the Cisco EX90, your computer peripherals are the functioning interface with the Video Conferencing software. If you are using a hardware codec – such as with the LifeSize Room 220, you have options for accessing the Video Conferencing software. Interfacing devices include a remote, a phone, an LCD screen, and your iPhone. Each manufacturer varies, and some offer more than one choice.


Each potential Video Conference participant will have access to Video Conferencing software that will interpret the data back and forth. Some of the software is hosted, as is the LifeSize Connections client, some is desktop-based, such as the Polycom m100, and some is housed in a piece of hardware, also referred-to as a codec, such as the Cisco Quick Set SX20. No matter the method of interpretation, the data is transmitted over the internet. At each end of the data transmission, the software will encode to send and decode to receive – thus the term codec.


With multiple locations involved, the participants must consider the hurdles of firewall and NAT traversal. Quick side note – a firewall and NAT traversal are protective layers in a network to protect your hardware (and data) from outside threats. Some Video Conferencing avenues have built-in firewall traversal – such as the Polycom HDX series room-based systems, while other systems offer hardware-based firewall traversal – such as the LifeSize Transit. If you are using a system that does not have built-in firewall traversal, such as the LifeSize Passport, you can open ports in your firewall (on both ends) to allow for video data to pass freely from one system to another. It sounds complicated, and step-by – step instructions are included with each system.


This is a term heard frequently when discussing Video Conferencing. A system that is Standards-Based is one that uses the same set of communication rules as defined by the International Telecommunications Union (ITU) to guarantee interoperability with other systems by the same and other manufacturers. These rules include the use of both SIP and H.323 to connect video calls.

Video Compression

How does all that data make it back and forth and at such a low bandwidth? The magic of Video Compression makes it possible. Your codec handles the encoding and decoding – or compression and decompression – at either end.

Video is merely a series of still images played at a rate that recreates natural movement. There is an indiscernible lag in the Video Conference which is so tiny that it is not detectable. This fact allows your brilliant Video Conferencing system to detect repetitive images, such as the picture on the wall behind you, and reuse the already-sent data for encoding and decoding images instead of resending all the image data for every shot. This helps to minimize the amount of bandwidth needed for a Video Conference.

Side note – when your Video Conferencing system detects a drop in available bandwidth, it will collect extra information for use in recreating images to avoid holes in your video call.


While you are in a video call, participants can share data with the other participants through a feature creatively called Data-Sharing. If you are using a desktop-based system, you can share your desktop with the other call participants. If you are using a room-based system, you can attach an external video input – such as a computer, a DVD player, a DVR player, a VCR (yes these still exist), or an additional camera for use with a whiteboard. You can begin and end a data stream at any point during a Video Conference. All Video Conference systems can partake in data-sharing, although some require the user to purchase a license to send data.

The basics of how Video Conferencing works was a very brief and general overview. For more in-depth details of Video Conferencing topics, please take a look at our other titles including, “Types of Video Conferencing Systems,” and “Types of Video Conferencing Equipment.” Be sure to contact the experts at Video Conferencing Systems by calling 1(855) 820-8006 or by emailing [email protected].