Differences Between Video Optical Terminals and Network Video Servers
Composition and Functions of Video Optical Terminals and Network Video Servers
An optical terminal is a device used to convert optical signals and electrical signals to each other, without any compression of the transmitted signals.
A network video server is a device used to digitize analog signals and compress digital signals.
Optical terminals are divided into optical transmitters and optical receivers. The optical transmitter receives 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 performs MPEG digital compression encoding before network transmission. 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 optical fiber and then converted back into a video signal by the receiving end of the optical terminal for display on a 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 is used to encode the video data with a high compression ratio while meeting the technical indicators required for network transmission. Previously, network video servers generally used encoders such as M-JPEG, which could not achieve higher compression bit rates suitable for various network environments, and could only achieve mediocre network transmission effects by reducing frame rates. Currently, various companies have launched MPEG4 network video servers to better meet the requirements of video network transmission.
Network Interface: Since previous 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: The network video server has 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: The network video server has an RS422/RS485 serial communication interface, which can connect external devices such as pan-tilt heads and speed domes via communication cables.
Network surveillance video servers can be used with computer central control software to implement large-scale system networking solutions. Some manufacturers provide open SDKs for network video servers, allowing 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 optical terminals can achieve real-time transmission, while network video servers generally cannot. The main reason is bandwidth; local area networks can perform slightly better.