What is the difference between a Video Optical Terminal and a Network Video Server?

Composition and Function of Video Optical Terminal and Network Video Server

　An optical terminal is a device used to convert optical signals and electrical signals to and from each other, without any compression of the transmitted signal.
　A network video server is a device used to digitize analog signals, compressing the digital signals.
An optical terminal consists of an optical transmitter and an optical receiver. The optical transmitter accepts electrical signals and converts them into optical signals for transmission over optical fiber. The optical receiver does the reverse.
A network video server accepts analog audio and video signals, which can be obtained directly from cameras and monitoring microphones, and transmits them over the network after MPEG digital compression encoding. It generally has an RJ45 interface, optical fiber FC interface, and SCSI interface (for external hard disk front-end storage). It is the optimal device for remote network surveillance systems.

　An optical terminal has two parts: one for transmission and one for reception, connected via optical fiber. The transmitting end of the optical terminal converts the camera's video signal into an optical-electrical signal, which is transmitted over the optical fiber and then converted back into a video signal by the receiving end of the optical terminal, reaching the monitor. It is mainly used for long-distance transmission, such as over several kilometers.
A network video server converts the camera's video signal into a digital signal and transmits it over the network, allowing video images to be viewed via IE browser.

Composition of a Network Video Server:

　　A network video server is a dedicated device that implements audio/video data encoding and network transmission processing. It consists of an audio/video codec, network interface, audio/video interface, RS422/RS485 serial interface, RS232 serial interface, etc.

　　Audio/Video Compression Codec: Since analog video data is extremely large in volume, and after digital-to-analog conversion the data volume remains large, mature encoding technology must be used to encode the video data at a high compression ratio while meeting the technical indicators required for network transmission. Earlier network video servers generally used encoders such as M-JPEG, which could not achieve higher compression bitrates suitable for various network environments, and could only achieve mediocre network transmission results by reducing the frame rate. Currently, various companies have launched MPEG4 network video servers to better meet the requirements of video network transmission.

　　Network Interface: Since earlier analog products were mainly networked through the establishment of expensive dedicated optical fiber for network transmission, the Ethernet interface of a network video server can conveniently implement IP networking and data transmission. Network video servers mainly use protocols such as TCP/IP to achieve network transmission of audio/video data, control data, and status detection information.

　　Audio/Video Interface: A network video server comes with standard analog audio/video input interfaces, facilitating monitoring of video signals on each channel. The NVS900 adopts Dynamic Stream Control technology to ensure real-time bidirectional audio transmission, with video frame rate automatically adjusted according to bandwidth, and automatic reconnection after network interruption.

　　RS422/RS485 Serial Interface: A network video server comes with an RS422/RS485 serial communication interface, allowing external devices such as pan-tilt heads and speed domes to be connected via communication cables.

　　A network surveillance video server can be used with computer central control software to implement large-system networking solutions. Some manufacturers provide open SDKs for network video servers, enabling users or third-party vendors to develop and build new application methods.

　　　The difference is that one requires cabling while the other does not, but an optical terminal can achieve real-time transmission, while a network video server generally cannot. The main reason is bandwidth; local area networks can perform slightly better.