Video Switcher Introduction

The video switcher is a key device that constitutes the main console in the control center, and is the device that selects the video image signal. Simply put, several video signals are input, and one of the video signals is selected for output by controlling it. In a TV monitoring system composed of multiple cameras, it is generally not necessary to use the same number of cameras as the cameras to display the image signals of the cameras of each channel. If so, the cost is high, the operation is inconvenient, and it is easy to cause confusion, so in general, a monitor is used to alternately display the image signals of several cameras according to a certain ratio. Video switches now mostly use analog switches made of integrated circuits. This form of switching control is convenient, and it is convenient to form a matrix switching form. The switching control signal can be coded.

The video switcher on the main console currently used is generally made into a matrix switching form and a building block type. According to the number of cameras in the system and the ratio of the camera to the monitor, the number of input and output channels of the video switcher and the arbitrary composition switching ratio can be selected.

The main technical indicators of the video switcher:
1. Switching ratio, this index refers to the number of input channels of the switch and the number of output channels after switching. If it is a matrix-type video switcher, the switching ratio can be arbitrarily selected through coding. If the switching ratio is fixed, the commonly used ones are "four choose one", "six choose one" and so on.

2. Isolation: This indicator measures the degree of isolation between multiple video signals and between them and the output signal after switching when multiple video signals are input to the switch. Generally expressed in decibels (dB), the higher the index value, the better.

3. Differential gain DG, differential phase DP Differential gain DG refers to the degree of distortion in amplitude between the video signal output after being switched and the signal before switching. The smaller the value of this indicator, the smaller the distortion.

Differential phase DP refers to the distortion in phase of the video signal output after being switched and the signal before switching. The smaller the value of this index, the smaller the distortion in phase. Generally, DG≤8% and DP≤8 ° of the video switcher used in the TV monitoring and control system are required.

4. Input level and output level Some video switchers also give technical indicators of input level (or input voltage) and output level (or output voltage). The input level refers to the input video signal voltage amplitude requirements of the video switcher, generally 0.8Vp-p to 1.2Vp-p; the output level refers to the output voltage amplitude standard of the video switcher output, generally 1Vp -p to 1.2Vp-p.