Security Video Surveillance System Digital Multiplexing and Image Processor
Digital multiplexing processor, that is, the aforementioned frame field switching processor. In practical applications, the frame-field switching processor must be used in conjunction with a video recorder, which can switch multiple video signals from each monitoring point at frame (field) intervals and record them with a video recorder. When performing video playback, the video signal output by the video recorder must pass through the frame-field switching processor to arbitrarily select a certain image to watch. At this time, the playback image will still have a slight stagnation (the so-called cartoon effect), which is due to Due to dropped frames (fields). Common frame switching processors are mostly 8-channel and 16-channel, while field switching processors are mostly 4-channel and 8-channel. Some frame-field switching processors can provide multi-screen display on the same screen while performing frame-field switching recording Function. The principle of multi-screen display on the same screen is the same as that of the screen splitter introduced earlier.
- Frame Switcher
The frame switcher switches the input video signals at the time interval of the frame period (40ms) of the TV signal, so that the selected signal is sent to the output port. The output port is directly connected to the video signal input port of the video recorder, so the video recording will be multiple video signals rotated at frame intervals.
The frame switcher has two basic functions: one is to cooperate with a video recorder to record multiple video signals by frame switching; the other is to automatically switch the alarm. Generally, while performing frame switching recording, it is required to be able to monitor each video signal on the same screen or alternately; during video playback, it is required that the playback screen should be as continuous as possible. In addition, some frame switchers can also provide the function of zooming in on a part of the screen by 2 times during single-screen playback, which is convenient for careful viewing of the details of a recorded image.
- Field switcher
The working principle of the field switcher is similar to that of the frame switcher, but the switching interval is based on the field of the image, that is, 20ms. Since the switching time interval is reduced by half, the cartoon effect is twice as good as that of the frame switcher during video playback. For example, when switching video playback through 4 channels, the repetition interval of each picture of the same channel image is 20×4=80ms, which is equivalent to a field repetition frequency of 12.5Hz, so that the picture seen by the human eye is basically smooth.
Since the signal formats of the odd and even fields are slightly different, the synchronization requirement of the field switcher for the odd and even field is higher than that of the frame switcher for adjacent frames. Theoretically, each video signal can be switched by line interval, that is, each line of video signal corresponds to one camera picture, so that there will be no frame loss or field loss, but the vertical resolution of the image will decrease, such as 4-channel Line switching will reduce the vertical resolution of the image to 1/4 of the original, which is similar to the effect of ordinary four-split single-channel playback, and the cost of equipment will be very high, so there is basically no such product.
- Image processor
The image processor is a device that synthesizes multiple video signals for recording and monitoring. Its basic parameters are:
The number of input video signal channels, according to different models, there are 4916 channels and other specifications:
simplex or duplex;
color or black and white;
image_effect(pixel);
Whether there is a video motion alarm function, etc.
The image processor contains all the functions of the multi-viewer, thus replacing the multi-viewer in most cases.