A video server is a computer based device (also called a "host") dedicated to delivering video.
Unlike personal computers, being multi-application devices, a video server is designed for one purpose; provisioning video, often for broadcasters. A professional grade video server records, stores, and playout of multiple video streams without any degradation of the video signal. Broadcast quality video servers often store hundreds of hours of compressed audio and video (in different codecs), play out multiple and synchronised simultaneous streams of video by, and offer quality interfaces such as SDI for digital video and XLR for balanced analog audio, AES/EBU digital audio and also Time Code. A genlock input is usually provided to provide a means of synchronizing with the house reference clock, thereby avoiding the need for timebase correction or Frame synchronizers.
Video servers usually offer some type of control interface allowing them to be driven by broadcast automation systems that incorporate sophisticated broadcast programming applications. Popular protocols include VDCP and the 9-Pin Protocol.
They can optionally allow direct to disk recording using the same codec that is used in various post-production video editing software packages to prevent any wasted time in transcoding.
In the TV broadcast industry, a server is a device used to store broadcast quality images and allows several users to edit stories using the images they contain simultaneously.
The video server can be used in a number of contexts, some of which include:
- News: providing short news video clips as part of a news broadcast as seen on networks (like CNN and Fox News).
- Production: enhance live events with instant replays and slow motion and highlights (sport production) (see OB Vans)
- Instruction: delivering course material in video format.
- Public Access: delivering city specific information to residents over a cable system.
- Surveillance: deliver real-time video images of protected sites.
- Entertainment: deliver film trailers or music videos.
Typically, a video server can do the following:
Generally, they have several bi directional channels (record and ingest) for video and audio. A perfect synchronisation is necessary between those channels to manage the feeds.
In the surveillance context, an IP video server converts analog video signals into IP video streams. The IP video server can stream digitized video over IP networks in the same way that an IP Camera can. Because an IP Video server uses IP protocols, it can stream video over any network that IP can use, including via a modem for access over a phone or ISDN connection. With the use of a video server attached to an analog camera, the video from an existing surveillance system can be converted and networked into a new IP surveillance system.
In the video security industry a video server is a device to which one or more video sources can be attached. Video servers are used to give existing analog systems network connectivity. Video servers are essentially transmission/ telemetry / monitoring devices. Viewing is done using a web browser or in some cases supplied software. These products also allow the upload of images to the internet or direct viewing from the internet. In order to upload to the internet an account with an ISP (internet service provider) may be required.