VIDEO CONFERENCING
VideoConference Equipment
In its most basic form a videoconference transmits the images and the voices of the participants to a remote site. Optional image sources include images / video programs. Data from a PC may also be provided. A basic conference requires:
- Main Camera
- Video Display
- Audio Components (e.g. speaker, microphone)
- The Codec
Main Camera
The most common video source is a single main camera that captures live movement occurring at one end so that it may be sent to the other end in near real-time.
The most important component of the camera is the image sensor which captures snapshots of the view in regular intervals (25-30 times per second.) This sensor is characterized by the number of pixels or dots that it can distinguish in an image, called the resolution. Typical resolutions are 640x480 pixels for webcams, 720x480 for NTSC cameras and 720x576 for PAL cameras.
The Video Display
A videoconferencing solution must include the ability to display the remote video that is being received. This incoming video is displayed on a monitor, most often a computer monitor or a TV, which influences how clearly the remote site can be seen and also how many people at the receiving site can easily see it.
Video resolutions supported by the popular videoconferencing standards H.323 are CIF (352 X 288 pixels) and QCIF (176 by 144 pixels.) Since these resolutions are fixed, increasing the network bandwidth of a call beyond a certain point will not show an appreciable difference in video quality within any given video frame. However, additional bandwidth enables higher frame rates (i.e., the sending of additional video frames per second), which can have dramatic improvements on the smoothness and video quality of motion.
Audio Components
Within a videoconference audio is as important, and often considered more important, than video. If we lose video or experience poor video quality in a conference but audio remains intact, we can still accomplish many of our communication objectives. The conference would simply become a teleconference rather than a videoconference. In contrast, poor or disrupted audio quality effectively shuts down a videoconference, often sending participants scrambling to find a "native audio" telephone to complete the meeting.
- Audio Vs Video
Within a videoconference audio is as important, and often considered more important, than video. If we lose video or experience poor video quality in a conference but audio remains intact, we can still accomplish many of our communication objectives. The conference would simply become a teleconference rather than a videoconference. In contrast, poor or disrupted audio quality effectively shuts down a videoconference, often sending participants scrambling to find a "native audio" telephone to complete the meeting.
The CODEC
The CODEC has two components the Coder and the Decoder. The Coder takes the local sound and vision signals and converts them into a form that can be transmitted over a digital network. The Decoder performs the reverse function i.e. it takes the remote site's digital signals from the network and converts or decodes them into a form that enables the local picture monitor to display images and the loudspeaker to radiate sound from the remote site.
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