1.2


Gaining advanced and important functionalities


A video encoder converts and compresses analog video signals into a video stream that is identical to that coming from a network camera, enabling it to be fully integrated into a network video system. This enables users to view live images on any local or remote computer on a network. A video encoder can also provide a multitude of advanced functionalities, such as distributed video motion detection, tam- pering alarm, event management, and integrated audio support. Furthermore, it provides a foundation for more intelligent video functionalities such as number plate recognition and people counting, etc.


Many video encoders offer pan/tilt/zoom (PTZ) control that allows analog PTZ cameras to be controlled over the network using a computer mouse or joystick. And if the video encoder supports Power over Ethernet (PoE), it may be possible for both the encoder and the analog camera that is connected to it to receive power through the same cable used for data transmission. This can provide substantial savings because power cables can be excluded from an installation.


Figure 2. Analog camera with a one-channel video encoder in a camera housing.


In terms of image quality, some video encoders provide image fine-tuning, as well as aspect ratio cor- rection that ensures that images do not appear distorted when viewed on a PC screen. High-performance video encoders provide full frame rate (30 fps in NTSC, 25 fps in PAL) in all resolutions for all video chan- nels. Furthermore, unlike their analog counterparts, digital images retain their quality regardless of the distance travelled.


The most common video encoder is a standalone version with single or multi-channel connections to analog cameras. Standalone video encoders are best positioned close to the analog cameras. They are typically used in situations where there are a few analog cameras located in a remote facility, or where the setup is some distance from the central monitoring room.


For larger centralized systems, high-density rack solutions with blade versions of the encoders are usu- ally preferred. The blades can support one, four or six channels. Racks can be outfitted with a mix of video encoder blades and can accommodate from one up to 84 analog channels, providing a flexible and expandable solution for migrating large-scale analog installations to network video. With hot swapping, there is no need to power down the entire system when installing or removing the video encoder blades.


1.3 Scalable and flexible


The introduction of video encoders improves scalability and flexibility. In an IP system it is very straight- forward to add new cameras and move them around in. This makes installation easier and facilitates an expansion of the system. Since recording and management is based on standardized computer hardware, the operator has a multitude of vendors and providers to pick from whenever more storage is needed or if other parts of the infrastructure must be upgraded.


Unlike analog CCTV/DVR systems, network video surveillance is built on open and interoperable stan- dards; video encoders use universally accepted compression standards such as Motion JPEG, MPEG-4 or H.264, enabling great savings in bandwidth and storage. Using standards also means that operators avoid the risk of being stuck with a proprietary technique. It also allows for integration with other sys- tems, for instance IP-based building management systems or industrial and logistical solutions. The possibility to combine and integrate different systems gives great leverage to a surveillance investment based on network video.


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