Large-scale Digital Video Switching Matrix Technology Based on IP address Switching

1. From circuit switching technology to group Switching Technology

The most basic application of circuit switching is that a signal occupies one line. This physical line is occupied by this signal until the electronic switch switches to another signal. This signal can be a digital signal or analog signal. To transmit multiple signals on a physical line and improve the utilization of the line, one method is to use the frequency division multiplexing technology to modulated multiple signals into different frequencies, for transmission over a line, the signal source can be a digital signal or analog signal. Another method is to use time-division multiplexing technology, the time-division multiplexing technology is divided into fixed-time-division multiplexing technology and statistical time-division multiplexing technology. The transmitted signal is a digital signal, and the analog signal must be digitalized for post-transmission.

The most typical application of fixed-time-division multiplexing technology is the telephone network that has been running for more than a hundred years. It is also a classic of circuit switching: when users require sending information, the switch establishes a physical data transmission channel with a fixed time slot between the caller terminal and the called user terminal. This channel is a fixed bandwidth, regardless of whether there is data transmission or how big the data transmission is, it occupies and only occupies the fixed bandwidth until the caller terminal and the called user terminal terminate the connection.

Statistical time-division multiplexing technology is the basis of all group exchange technologies. The difference between group exchange technologies is only the difference in packet formats, and the difference in processing control. No fixed time slots are allocated between the caller and the called user, and the bandwidth is dynamically adjusted according to application requirements. In recent decades, the group exchange technology has experienced X.25, FR Frame Relay), ATM asynchronous transmission mode, and so on. With the development of optical communication technology and the popularization of the INTERNET, IP address applications based on group exchange technology are absolutely dominant.

Compared with circuit switches, group switches consume less bandwidth and have higher transmission efficiency. Therefore, group switches will replace Circuit switches.

2. Features of analog video switching matrix based on Circuit Switching

In traditional video image monitoring, video signals are always in the form of analog signals. The emergence of the analog video switching matrix is an epoch progress in the development history of Video Image Monitoring. Its main feature is multi-channel M-channel analog video image input, single-channel or multi-channel N-channel) video image output. Generally, N outputs are less than M inputs. According to the preset rules, N outputs are switched to any input in M, this allows you to monitor all M-Channel Video images. M may be very large, but it is very costly to display M-path images at the same time. From the perspective of application placement, it is not necessary to continuously monitor the same image, the video Switching Matrix meets this requirement. For example:

Medium M-path image video image input and N-path image output. N output video images can be connected to the MONITOR for real-time monitoring by security personnel, or to the hard disk recorder of the video recorder. Any path in N-way output image can come from any path in M-way image. The switching rule can be programmed in advance and controlled by the microprocessor.

The simulated switching matrix is easy to implement and easy to use. Currently, the number of switches in a switching matrix is very high, and more than 1000 switches can be achieved.

It can be seen that the input/output of video signals are analog signals. How can we switch the remote video image signal as the broadband network develops today? It is unrealistic to transmit all remote video image signals using analog signals, which requires network transmission technology.

3. IP switching-based digital video switching matrix technology

With the development of broadband technology, the demand for remote centralized monitoring is increasing and the scale is growing. One is to rebuild the private network and use the existing CATV technology, including the WDM Technology, directly transmit analog signals without processing to the monitoring center for centralized monitoring. The disadvantage is that the network construction cost is very high and the WDM Technology must be passive in the middle of bare optical brazing ), in some applications, it is feasible in a small area, but the cost of centralized monitoring is high. Another method is to use the existing digital network to digitally compress audio and video signals, and compress the bitstream into IP packets through the TCP/IP protocol, transmit these IP packets to the monitoring center for real-time decoding of video images for centralized monitoring. The digital network can be VPN, private network, or public network, such as PSTN, ISDN, GPRS, CDMA, ADSL, broadband MAN, and INTERNET.

Is a typical application:

In the Application diagram above, the PC management host can configure, manage, and control each video server at the front end through an IP network, and monitor the video images of each video server in real time. If there are too many video images and the entire network is too large, a management host can monitor the images of many video servers at the same time and display the video images through a PC display, and switch the image signal through preset rules. For example, if switching is performed once every 15 seconds, one cycle is required. a pc can perform 16-way decoding computing at the same time, and a PC can monitor 64-Channel Video images at the same time, the two PCs can monitor the 128-channel video image, and so on.

If multiple video decoding cards are inserted into the PC, the video decoding card supports avoutput and can form a TV wall. multiple PCs can form a huge TV wall for centralized monitoring and management.

4. The era of analog video switching matrix to digital video Switching Matrix

The simulation of centralized monitoring is often a building, a compound, and a residential area. When the scope exceeds a certain distance, the simulation of centralized monitoring is very costly and difficult to implement ).

With the development of the following technologies, the era of digital video switching matrix has been promoted:

1. The development of video compression technology, the implementation of real-time compression of video images, the greatly reduced video image compression code streams, and reduced network bandwidth requirements;

2. With the development of network technology, the coverage of IP networks is still expanding, and the cost of network transmission is continuously decreasing;

3. The development of streaming media technology is more controllable.

Compared with the analog video switching matrix, the digital video switching matrix has the following advantages:

Digital Monitoring can use existing networks without the need to create a transmission network for Image Monitoring. As long as the IP network can be covered, you can perform centralized monitoring, including through the INTERNET.

1. Integration of Circuit Switching Technology and group Switching Technology
2. Exchange Technology-introducing the evolution of Exchange Technology