I. Video signal interface
Monitoring video line types introduction:
According to the materials, SYV and SYWV are divided into two types. The physical layer structure of the insulation layer is different. SYV is a solid polyethylene cable. SYWV is a high-physical foam cable, and the physical foam cable has better transmission performance than polyethylene.
The S--coaxial cable Y--polyethylene V--polyvinyl chloride W--stable polyethylene can be classified into SYV50-XXSYV75-XXSYV-100XXXX according to the impedance representing the outer diameter of the insulation layer.
1. Composite video signal: General connector is BNC, RCA (Lotus head)
75 stands for resistance, followed by 3 and 5 for its insulating outer diameter (3mm/5mm).
SYV S - coaxial RF cable, Y - polyethylene, V - PVC.
SYV75-3 transmission is effective within 200 meters.
SYV75-5 transmission is better within 500 meters.
Video line 75-3 (about 200 meters) Transmission distance 75-5 (about 500 meters) Transmission distance 75-7 (about 500--800 meters) Transmission speed 75-9 (about 1000 --- 1500 meters) Speed distance 75-12 (about 2000----3500 meters) speed transmission distance 2.S- terminal (or Y/C)
Its scientific name is called "two-component video interface", commonly known as the S-Video transmission distance is shorter than 15 meters S-Video connection specification is a specification developed by the Japanese, S refers to the "SEPARATE (separation)", it will brightness and color The output is separated to avoid the mutual interference of luminance and chrominance when the hybrid video signal is output. The S interface is actually a five-wire interface and is composed of five luminance lines, two video color signals, and a common shield ground line.
Compared with the AV interface, since it is no longer Y/C mixed transmission, it does not need to perform bright color separation and decoding work, and the use of independent transmission channels largely avoids signal crosstalk in the video equipment. The distortion of the image greatly improves the sharpness of the image. However, S-Video still needs to combine the two channels of color difference signals (CrCb) into one channel of color signal C, and then transmit it to the Cb and Cr in the display device for processing. This will still cause some signal loss and distortion. (This distortion is small but can still be found when testing under strict broadcast video equipment). Moreover, since the mixing of CrCb leads to a certain limitation on the bandwidth of the chroma signal, S-Video, although it is already excellent, is far from perfect. Although S-Video is not the best, it is still one of the most popular video interfaces, taking into account current market conditions and other factors such as overall cost.
3.VGA signal VGA (Video Graphics Array) is a video transmission standard that IBM introduced with the PS/2 machine in 1987. It has the advantages of high resolution, fast display speed, and rich colors. It has been widely used in the color display field. Applications.
High frequency and easy attenuation, short transmission distance and easy interference 3+4/6VGA15-30M
4. Component video (RGBHV signal)
The color difference interface is based on the S interface, and transmits the blue difference (b) and the red difference (r) in the chroma (C) signal separately, and the resolution thereof can reach 600 lines or more. It usually uses two labels YPbPr and YCbCr. The former represents the progressive color difference output, and the latter represents the interlaced color difference output. Nowadays, many television products rely on the input of color difference to improve the quality of the input signal, and through the color-difference interface, multiple levels of signals can be input. From the most basic 480i to 480p of frequency-doubled scanning, even 720p, 1080i, etc. are all It is only through the input of color difference that there is a way to send the signal to the TV.
75-2RGB30-50M
75-3RGB50-70M
5.DVI
◎ DVI-A (Analog, analog) interface: This interface is actually a deformation of the VGA interface, previously used for some high-end CRT monitors, but now basically eliminated. We often say that "false DVI interface" refers to DVI-A because it still transmits analog signals instead of digital signals that show the advantages of DVI technology.
◎ DVI-D (Digital) Interface: DVI-D is a digital signal interface in the true sense. This is a more advanced place than DVI-A. However, the DVI-D interface also has its disadvantages. That is when the user uses the interface. Can not be compatible with the old-fashioned CRT monitor, if it happens that the LCD monitor only has D-Sub interface, then the user is only dry eyed.
◎DVI-I (Integrated) Interface: This is a hybrid interface that combines DVI-A and DVI-D. It is compatible with DVI-D and DVI-A (via adapter Switching to D-Sub) is the best compatible DVI interface. Generally speaking, there is no obvious difference between using single-channel DVI and dual-channel DVI when transmitting video signals below 1600×1200@60Hz. If your monitor can support FullHD (1920×1080) or above resolution, do not choose single-channel DVI data cable.
DVI-D: Can only receive digital signals DVI-I: Can simultaneously receive digital signals and analog signals Transmission distance is short 7-15M
6.HDMI
Uses the same underlying protocol as the DVI digital signal, so it can also be interchanged with the DVI signal through the adapter and compatible with the DVI signal. More powerful than the DVI interface, HDMI allows the transmission of high-fidelity audio signals over the HDMI cable when the communication protocol is established. The seamless connection reduces the connection trouble and also makes HDMI more widely compatible.
Supports 5Gbps data rates, up to 15 meters. Compared with DVI, HDMI can transmit digital audio signals and adds support for HDCP while providing better DDC optional features. HDMI supports data transmission rate of 5Gbps and can transmit up to 15 meters, enough to handle one 1080p video and one 8-channel audio signal. And because the demand for a 1080p video and an 8-channel audio signal is less than 4GB/s, there is still a lot of room for HDMI. This allows it to use one cable to connect the DVD player, receiver and PRR, respectively. In addition, HDMI supports EDID and DDC2B. Therefore, HDMI-equipped devices have the feature of “plug and play”, and the “negotiation” between the signal source and the display device is automatically performed, and the most suitable video/audio format is automatically selected.
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 broadcast-grade camera. It is another technological advancement in the field of security monitoring, providing high-definition image source equipment for the monitoring center.
II. Control signals
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 20 Kbps. The interface uses a signal line and a signal return line to form a common ground transmission format. This common ground transmission is prone to common mode interference, so the resistance Noise interference is weak. Transmission distance 15 meters to 20 meters. When using a 150pF/m communication cable, the maximum communication distance is 15m; if the capacity 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 communications within 20m.
RS-422 is differential mode transmission, strong anti-interference ability, can transmit 1200 meters, the maximum transmission rate is 10Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate. Below 100 kb/s, it is possible to reach the maximum transmission distance. The highest rate transmission can only be achieved at a short distance. The maximum transmission rate that can be obtained on a typical 100-meter long twisted pair is only 1 Mb/s.
The maximum communication distance of RS-485 is about 1219 meters, and the maximum data transmission rate is 10Mbps. The RS-485 interface uses a combination of balanced drivers and differential receivers. The resistance to common mode interference is enhanced, that is, the noise immunity is good.
CR-NET (CREATOR control signal) transmission distance is 800 meters.
