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What is a video encoder?


Video encoders, also known as video servers, enable an existing analog CCTV video surveillance system to be integrated with a network video system. Video encoders play a significant role in installations where many analog cameras are to be maintained.

A video encoder makes it possible for an analog CCTV system to migrate to a network video system. It enables users to gain the benefits of network video without having to discard existing analog equipment such as analog CCTV cameras and coaxial cabling.

A video encoder connects to an analog video camera via a coaxial cable and converts analog video signals into digital video streams that are then sent over a wired or wireless IP-based network (e.g., LAN, WLAN or Internet). To view and/or record the digital video, computer monitors and PCs can be used instead of DVRs or VCRs and analog monitors.

Integration of analog cameras and monitors with a network video system using video encoders and decoders
An illustration of how analog video cameras and analog monitors can be integrated with a network video system using video encoders and decoders.

By using video encoders, analog video cameras of all types, such as fixed, indoor/outdoor, dome, pan/tilt/zoom, and specialty cameras such as highly sensitive thermal cameras and microscope cameras can be remotely accessed and controlled over an IP network.

A video encoder also offers other benefits such as event management and intelligent video functionalities, as well as advanced security measures. In addition, it provides scalability and ease of integration with other security systems.

Standalone video encoder
A one-channel, standalone video encoder with audio, I/O (input/output) connectors for controlling external devices such as sensors and alarms, serial ports (RS-422/485) for controlling PTZ analog cameras and Ethernet connection with Power over Ethernet support.

Video encoder components and considerations

Axis video encoders offer many of the same functions that are available in network cameras. Some of the main components of a video encoder include:

  • Analog video input for connecting an analog camera using a coaxial cable.
  • Processor for running the video encoder’s operating system, networking and security functionalities, for encoding analog video using various compression formats and for video analysis. The processor determines the performance of a video encoder, normally measured in frames per second in the highest resolution. Advanced video encoders can provide full frame rate (30 frames per second with NTSC-based analog cameras or 25 frames per second with PAL-based analog cameras) in the highest resolution for every video channel. Axis video encoders also have auto sensing to automatically recognize if the incoming analog video signal is an NTSC or PAL standard. For more on NTSC and PAL resolutions, see NTSC and PAL resolutions.
  • Memory for storing the firmware (computer program) using Flash, as well as buffering of video sequences (using RAM).
  • Ethernet/Power over Ethernet port to connect to an IP network for sending and receiving data, and for powering the unit and the attached camera if Power over Ethernet is supported. For more on Power over Ethernet, see PoE.
  • Serial port (RS-232/422/485) often used for controlling the pan/tilt/zoom functionality of an analog PTZ camera.
  • Input/output connectors for connecting external devices; for example, sensors to detect an alarm event, and relays to activate, for instance, lights in response to an event.
  • Audio in for connecting a microphone or line-in equipment and audio out for connecting to speakers.

Video encoders for professional systems should meet high demands for reliability and quality. When selecting a video encoder, other considerations include the number of supported analog channels, image quality, compression formats, resolution, frame rate and features such as pan/ tilt/zoom support, audio, event management, intelligent video, Power over Ethernet and security functionalities.

Event management and intelligent video

One of the main benefits of Axis video encoders is the ability to provide event management and intelligent video functionalities, capabilities that cannot be provided in an analog video system. Built-in intelligent video features such as multi-window video motion detection, audio detection and active tampering alarm, as well as input ports for external sensors, enable a network video surveillance system to be constantly on guard to detect an event. Once an event is detected, the system can automatically respond with actions that may include video recording, sending alerts such as e-mails and SMS, activating lights, opening/closing doors and sounding alarms.

Next topic: Standalone video encoders

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