First, the video signal interface
Monitoring video line type introduction:
According to the material, there are two kinds of SYV and SYWV. The physical material structure of the insulating layer is different. SYV is a solid polyethylene cable; SYWV is a high physical foaming cable, and the physical foaming cable has better transmission performance than polyethylene. (S--coaxial cable Y--polyethylene V--polyvinyl chloride W--stable polyethylene)
According to the impedance, it can be divided into SYV 50-XX SYV 75-XX SYV-100 XX......XX represents the outer diameter of the insulation layer.
1. Composite video signal: general connector is BNC, RCA (lotus head)
75 represents resistance, and the rear 3 and 5 represent its outer diameter (3 mm/5 mm). Video line points:
75-3 transmission distance is about 200 meters;
75-5 transmission distance is about 500 meters;
The speed of 75-7 is about 500-800 meters;
75-9 transmission speed is about 1000---1500 meters;
The speed of 75-12 is about 2000----3500 meters.
2, S-terminal (or Y/C)
Its scientific name is called "two-component video interface", commonly known as S-terminal, and the transmission distance is 15 meters short.
The S-Video connection specification is a specification developed by the Japanese, and S refers to "SEPARATE", which separates the luminance and chrominance output, thereby avoiding mutual interference of luminance and chrominance when the mixed video signal is output. The S interface is actually a five-core interface consisting of two lines of brightness signals, two video chrominance signals, and one common shielded ground line.
Compared with the AV interface, since it does not perform Y/C hybrid transmission, there is no need to perform bright color separation and decoding, and the use of separate transmission channels largely avoids signal crosstalk in the video device. The image is distorted, greatly improving the sharpness of the image. However, S-Video still needs to mix two color difference signals (Cr Cb) into one chrominance signal C, transmit it and then decode it into Cb and Cr in the display device for processing, so that it still brings some signal loss. Distortion (this distortion is small but can still be found when testing under strict broadcast-quality video equipment). Moreover, due to the mixing of Cr Cb, the bandwidth of the chrominance signal is also limited, so S-Video is quite good, but it is far from perfect. Although S-Video is not good, it is one of the most popular video interfaces considering other factors such as current market conditions and overall cost.
3, VGA signal
VGA (Video Graphics Array) is a video transmission standard introduced by IBM in 1987 with PS/2. It has the advantages of high resolution, fast display speed and rich colors. It has been widely used in the field of color display, but Easy to attenuate, short transmission distance, and susceptible to interference. Its 3+4/6VGA transmission distance is 15-30M.
4, component video (RGBHV signal)
The color difference interface is based on the S interface, and the blue difference (b) and the red difference (r) in the chrominance (C) signal are separately transmitted, and the resolution can reach 600 lines or more. It usually uses two symbols, YPbPr and YCbCr, the former represents the progressive scan color difference output, and the latter represents the interlaced color difference output. Nowadays, many TV products rely on the color difference input to improve the input signal quality, and through the color difference interface, you can input multiple levels of signals, from the most basic 480i to the 480p of the multi-frequency scanning, even 720p, 1080i, etc. To pass the color difference input, there is a way to transmit the signal to the TV. The transmission distance of 75-2RGB is 30-50M, and the transmission distance of 75-3RGB is 50-70M.
5, DVI
DVI-A (Analog, analog) interface: This interface is actually a variant of the VGA interface. It used to be used on some high-end CRT monitors, but it has been basically eliminated. The "fake DVI interface" we often refer to is DVI-A because it still transmits analog signals, not digital signals that embody the advantages of DVI technology.
DVI-D (Digital) interface: DVI-D is a true digital signal interface, which is more advanced than DVI-A; however, DVI-D interface is also insufficient, that is, users can not use this interface Compatible with old-fashioned CRT monitors, if it happens to have a D-Sub interface on the LCD monitor, then the user will only have to blink.
DVI-I (Integrated) interface: This is a hybrid interface that combines DVI-A and DVI-D. It is compatible with both DVI-D and DVI-A (it can also be transferred through the adapter). Connected to D-Sub), is a good DVI interface for compatibility
In general, when transmitting video signals below 1600 × 1200 @ 60 Hz, there is no significant difference between using single-channel DVI and dual-channel DVI. If your monitor can support Full HD (1920×1080) or higher resolution, do not select a single-channel DVI cable. DVI-D can only receive digital signals; DVI-I can receive digital signals and analog signals at the same time, the transmission distance is short, 7-15M.
6, HDMI
It uses the same underlying protocol as the DVI digital signal, so it can also be interchanged with the DVI signal through the adapter and is compatible with DVI signals. More powerful than the DVI interface, HDMI allows high-fidelity audio signals to be transmitted over HDMI cables when developing communication protocols. Seamless connectivity reduces the hassle of wiring and makes HDMI more widely compatible. The transmission distance of the HDMI cable's near-lossless image quality is within 15 meters and the maximum length is 30 meters.
Compared to DVI, HDMI can transmit digital audio signals and add support for HDCP while providing better DDC options. HDMI supports 5Gbps data transfer rate, up to 15 meters, enough to handle a 1080p video and an 8-channel audio signal. And because a 1080p video and an 8-channel audio signal require less than 4GB/s, HDMI has a lot of headroom. This allows it to be connected to a DVD player, receiver and PRR with a single cable. In addition, HDMI supports EDID and DDC2B, so devices with HDMI have the characteristics of “plug and playâ€, and “negotiation†is automatically performed between the signal source and the display device to automatically select the most suitable video/audio format.
7, SDI
SDI (serial digital interface) is a "digital component serial interface". Then HD-SDI is a high-definition digital component serial interface. HD-SDI is a real-time uncompressed high-definition radio and television-grade camera. It is another technological advancement in the field of security monitoring, providing high-definition image source equipment for the monitoring center.
Second, the control signal
Common control signals, RS232, RS422, RS485, IR, CR-NET (CREATOR control signal)
The RS232 transmission rate is low. In asynchronous transmission, the baud rate is 20Kbps. The interface uses a signal line and a signal return line to form a common transmission form. This common transmission is prone to common mode interference, so it is resistant. Noise interference is weak. The transmission distance is 15 meters to 20 meters. When using a 150pF/m communication cable, the maximum communication distance is 15m; if the capacitance per meter of cable is reduced, the communication distance can be increased. Another reason for the short transmission distance is that RS-232 is a single-ended signal transmission, which has common ground noise and cannot suppress common mode interference. Therefore, it is generally used for communication within 20m.
RS-422 is a differential mode transmission with strong anti-interference ability. It can transmit 1200 meters and the maximum transmission rate is 10Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate, and it is possible to reach the maximum transmission distance below the 100 kb/s rate. The Zui high-rate transmission can only be obtained at a short distance. The maximum transmission rate that can be obtained on a typical 100-meter twisted pair is only 1 Mb/s.
The maximum communication distance of RS-485 is about 1219 meters, and the high transmission rate of data Zui is 10Mbps. The RS-485 interface is a combination of balanced driver and differential receiver, which has enhanced anti-common mode dry capability, that is, good anti-noise interference.
IR infrared (CREATOR central control infrared port) transmission distance of 150 meters.
CR-NET (CREATOR control signal) transmission distance of 800 meters.
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