RADVISION术语表

Glossary (V)

# - A - B - C - D - E - F - G - H - I - J - K - L - M - N
O- P - Q - R - S - T - U - V - W - X - Y - Z

VAD (VOICE ACTIVITY DETECTION)
Used in speech encoding software to determine if the voice being encoded is human speech or background noise.

VAS (VALUE ADDED SERVICE)
A telecommunication/information service that is offered in addition to and/or in conjunction with a basic telecommunication/data service.

V.35
An ITU standard for group band modems that achieve higher data rates by combining the bandwidth of several telephone circuits. Typically used for modem-to-multiplexer communication.
See also Serial Interface and X.21

VIDEO BIT RATE
Bit rate is the speed at which bits are transmitted, in bits per second.

VIDEO BLOG
A vlog or video blog is a blog (short for weblog) which uses video as the primary content. The video is linked within a video blog post and usually accompanied by supporting text, image, and additional metadata to provide context.

VIDEO BRIDGE
Computerized switching system which allows multipoint video conferencing.

VIDEO CHAT
A visually-enhanced online chat session.

VIDEO CONFERENCING
Communication across long distances with video and audio contact that may also include graphics and data exchange. Digital video transmission systems typically consist of camera, codec (coder-decoder), network access equipment, network, and audio system.

VIDEOPHONE
A videophone is a telephone which is capable of both audio and video duplex transmission.

VIDEO MAIL
Used in IP endpoint or to 3G mobile calling. When a destination is busy or receives no answer, the video call service picks up the call and broadcasts a pre-recorded message stating that the owner of the destination 3G mobile is unavailable. The video mail then begins recording the incoming video conference.

VIDEO ON DEMAND STREAMING
Delivery of a Video on Demand stream to a viewer upon request at any given time. Contrast this to a real-time stream that is delivered when the conference is in progress.

VIDEO TRANSRATING
Video Transrating adjusts the bitrate of video received from an IP network to maintain video quality on mobile networks. A key requirement for the connectivity of broadband and mobile networks.

VISITED NETWORK
In roaming, the network delivering the service on behalf of the home network.

VLAN (VIRTUAL LOCAL AREA NETWORK)
A method of creating independent logical networks within a physical network. Several VLANs can coexist within such a network. Used in many cases for media and management separation.

VOICE-ACTIVATED VIDEO SWITCHING
Automatic switching of a video image viewed at each conference terminal according to the voice level of each participant.

VOIP (VOICE OVER IP)
See IP Telephony

VPN (VIRTUAL PRIVATE NETWORK)
VPN modules create closed secure tunnels for communication between two firewalled LANs. VPN technology is one of the approaches being used today for providing secure communications over IP networks.

VXML
An XML language (Voice & Video XML) - a simple, yet powerful XML-based API, enabling the implementation of diverse video and voice services, while keeping the development task simple by relieving the developer from the need to deal with underlying complexities. It is based on HTTP protocol.