Video signal interface monitor video cable type introduction

Some time ago, a lot of weak friends often asked about the transmission distance of the interface. Today, we have come to a variety of video interface transmission distance.

First, the video signal interface monitoring video cable type description:

SYV and SYWV are divided into two types according to the materials. The physical layer structure of the insulating layer is different. SYV is a solid polyethylene cable. SYWV is a high-physical foaming cable. 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 can be divided into SYV 50-XX SYV 75-XX SYV-100 XX ... XX represents the outer diameter of the insulating 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). Video line points: 75-3 transmission distance of about 200 meters; 75-5 transmission distance of about 500 meters; 75-7 transmission speed of about 500--800 meters); 75-9 transmission speed of 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, the transmission distance is short 15 meters. The S-Video connection specification is a specification developed by the Japanese, and S refers to "SEPARATE (separation)", which separates luminance and chrominance output, avoiding 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 the generation of signal crosstalk in the video equipment. The distortion of the image greatly improves the sharpness of the image. However, S-Video still needs to mix the two channels of color difference signals (Cr Cb) into one channel of color signal C for transmission and then decode it into Cb and Cr in the display device for processing. This will still cause some signal loss and generate Distortion (This distortion is small but can still be found when testing under strict broadcast video equipment). Moreover, since the mixing of Cr Cb leads to a certain limitation on the bandwidth of the chroma signal, S-Video, although it is already relatively good, 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, but Easy to attenuate, short transmission distance, easily disturbed. 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 transmits the blue difference (b) and the red difference (r) in the chroma (C) signal separately, and its resolution 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 TV 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. The transmission distance of 75-2RGB is 30-50M, and the transmission distance of 75-3RGB is 50-70M.

5, DVIDVI-A (Analog, analog) interface: This interface is actually a deformation of the VGA interface, previously used for some high-end CRT monitors, but now has 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 the disadvantage that users cannot use this interface. Compatible with old-fashioned CRT displays, if you happen to have only a D-Sub interface on the LCD monitor, the user will only be able to take a look. DVI-I (Integrated) Interface: This is a hybrid interface that combines DVI-A and DVI-D. It is both compatible with DVI-D and DVI-A (via adapter Connecting 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 Full HD (1920×1080) or higher resolution, do not select the single-channel DVI cable. DVI-D can only receive digital signals; DVI-I can simultaneously receive digital signals and analog signals with a short transmission distance of 7-15M.

6, HDMI

Uses the same underlying protocol as the DVI digital signal, so it can also be interchanged with the DVI signal via the adapter and is compatible with DVI signals. More powerful than the DVI interface is that HDMI allows the transmission of high-fidelity audio signals via the HDMI cable when the communication protocol is established. The seamless connection reduces the connection trouble and also makes HDMI more widely compatible. Supports data transmission rate of 5Gbps and can transmit up to 15 meters. Compared with DVI, HDMI can transmit digital audio signals and add 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 4 GB/s, HDMI has a large margin. 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.

Second, the control signal

Common control signals, RS232, RS422, RS485, IR, CR-NET (CREATOR control signal) RS232 transmission rate is low, in asynchronous transmission, the baud rate is 20Kbps, the interface uses a signal line and a signal return line This forms a common ground transmission format. This common ground transmission is prone to common mode interference and therefore has weak noise immunity. 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-end 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, the maximum transmission distance is possible. 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. IR IR (CREATOR control infrared port) transmission distance 150 meters. CR-NET (CREATOR control signal) Transmission distance 800 meters.