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> 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.
5.1.2 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.
For more
on event management and intelligent video, see Chapter 11
.
5.2
Standalone video encoders
The most common type of video encoders is the standalone version, which offers one or multi-
channel (often four) connections to analog cameras. A multi-channel video encoder is ideal in
situations where there are several analog cameras located in a remote facility or a place that is
a fair distance from a central monitoring room. Through the multi-channel video encoder, video
signals from the remote cameras can then share the same network cabling, thereby reducing
cabling costs.
In situations where investments have been made in analog cameras but coaxial cables have not
yet been installed, it is best to use and position standalone video encoders close to the analog
cameras. It reduces installation costs as it eliminates the need to run new coaxial cables to a
central location since the video can be sent over an Ethernet network. It also eliminates the loss
in image quality that would occur if video were to be sent over long distances through coaxial
cables. With coaxial cables, the video quality decreases the further the signals have to travel.
A video encoder produces digital images, so there is no reduction in image quality due to the
distance traveled by a digital video stream.
VIDEO ENCODERS - CHAPTER 5
