Those engaged in broadcasting and television technology know that the television broadcasting control system is the heart of the television broadcasting system, and it is the hub for the collection of various signals such as program recording signals and broadcasting signals. The overall control matrix scheduling system is the core of the overall control system, serving as a bridge connecting the broadcasting control room and various studios within the station, as well as transmitting external signals through satellites, optical fibers, microwaves, and other means. Therefore, how to design and layout the TV signal matrix, and how it is applied, will directly affect whether the entire control system is convenient to use, whether it has a safe and reliable guarantee, and even reflect the technical level of a TV station's control system.

Classification of a Television Signal Matrix

The television signal matrix can be divided into two categories: analog composite video audio matrix and digital video matrix. Composite Video has good stability, compatibility, and versatility, with low requirements for equipment and transmission cables, and rich signal sources. The input and output video signals of the analog composite video audio matrix are all composite video signals, and the audio signals are generally balanced analog audio signals, which are applied to analog TV systems.

The input and output interfaces of the Digital Video matrix are all Serial Digital Interface (SDI). A coaxial cable can simultaneously transmit a digital component video signal and a 4-channel digital audio signal. SDI digital signals have the advantages of high video and audio signal quality and long-distance transmission, with no additional hardware required within a distance of 200 meters. Widely used in current digital television technology systems.

The common video signal matrices, according to the different input and output channels, generally include 8 * 8, 16 * 16, 32 * 16, 32 * 32, 64 * 32, 64 * 64, 96 * 96, 128 * 128, etc. The conventional understanding is that the number before the multiplication sign represents the number of input channels, and the number after the multiplication sign represents the number of output channels. The basic principle of designing a video matrix is to determine the number of channels in the matrix and reserve a certain amount of development space based on the number of signal sources and required terminals.

In addition, it can also be classified according to the purpose of the matrix. For example, the main control system matrix of Shenzhen TV is divided into input matrix, main control matrix, broadcast matrix, emergency switching matrix, etc. No matter how the matrices are classified, their control methods are roughly the same: front panel button control, separate keyboard control, third-party (computer) control, etc.

The Application of Two TV Signal Matrix in the Control System

A television station with a certain scale often requires its overall control system to be composed of multiple signal matrices. How to design, layout, and arrange the functions of the matrix will play a crucial role in the convenience and security of the entire system. Taking the Shenzhen TV control matrix system as an example, let's talk about the specific application of the control TV signal matrix.

1. Overall layout of the overall control TV signal matrix

The overall control matrix system of Shenzhen Television Station mainly consists of a 64 * 64 input matrix, a 128 * 96 main control matrix, and a 64 * 64 broadcast matrix. The layout diagram of its composition is shown in Figure 1.

The input matrix, control matrix, and broadcast matrix are all Leitch digital matrices. The input and output of this matrix are all SDI digital signals. Each matrix has a technical monitoring port (Tech. monitor) and an output monitoring port (Monitor Out). The technical supervision port can monitor each input signal, and the output supervision port can monitor each output signal. This matrix adopts dual power sources and provides hot backup for each other. When any group of power sources fails, the other group of power sources can automatically bear the full power of the matrix without the need for manual switching. In addition to the main control panel, the matrix can also be equipped with several sub control panels that control the output of a certain outlet signal, and can be connected to control the serial port of the computer to receive switching commands from the computer, which is very convenient to operate.

2. Input matrix

The input matrix is located at the front end of the matrix system and serves as an intermediary bridge for external signals such as satellites, optical fibers, microwaves, etc. to access the main control system. It mainly plays a role in accessing and monitoring external signals, transmitting programs to the outside world, and providing a directory control source for the station. The input signals of the input matrix in Figure 1 include external signals such as satellite reception signals, cable TV set-top box signals, fiber optic and microwave transmission from other TV bases, as well as 8 output signals from the main control matrix. This allows the input matrix to not only schedule external signals, but also indirectly schedule internal signals of the main control system through the main control matrix. Its output signal is mainly used for connecting with the main control matrix, external signal monitoring, signal communication with other external TV bases, and program recording signal sources. All input and output signals of the input matrix are not directly involved in television broadcasting, so all signals are not required to be synchronized with the main control system. But it has 8 output signals that are input into the main control matrix through a frame synchronizer. In this way, all signals in the input matrix can participate in signal communication within the main control system through the main control matrix and can be indirectly broadcasted. In addition to the main control panel, there is also a sub control panel at the section directory system end for the input matrix, making it very convenient to choose the recording signal source.

3. Main control matrix

The master matrix is the center of the matrix system. Its main function is to undertake signal communication within the main control system, the broadcasting halls on each floor of the building, and the main control system, and to a certain extent, play the role of input matrix and broadcast matrix, enhancing the flexibility of system application and enhancing the safety performance of the system.

The input signal of the main control matrix of Shenzhen TV station in the figure is mainly the output signal of the input matrix synchronized by the 8-channel synchronous machine, which can indirectly participate in signal communication within the system; The satellite signals synchronized by the 7-channel Jingzhen synchronous machine and 2 signals from each of the three external bases can allow external signals to be directly used and broadcasted within the system without going through the input matrix. Therefore, the main control matrix plays a certain backup role for the input matrix; There are also 20 main and backup signals from various broadcasting halls; 12 channels broadcasting video recorder signals; 20 channels broadcast server main and backup signals, as well as 20 channels broadcast up key signals and clean signals that have not been up key. It can be seen that the input signal of the main control matrix basically covers all signals within the system and some external signals that are frequently needed within the system. All input signals of the main control matrix are synchronized by the system and can be directly transferred to various channels for broadcasting.

The output signal of the main control matrix has 8 outputs to the input matrix, which can meet the requirements of the input matrix for internal signals in the system; 8-way output to the monitoring screen, which can monitor signals that are currently or are about to be broadcast, as well as those that need to be monitored; 12 output signals are sent to various external TV bases; 9-way output signals are sent to various broadcast channels for broadcasting, while also serving as a backup for the broadcast matrix; There are 10 output signals connected to the broadcast matrix, which can expand the input signal source of the broadcast matrix; 25 output signals are used for signal communication with various studios; There are also 3 outputs as upload signal sources for the broadcast server. The main control matrix has a main control panel, a sub control panel at the upload end that controls the selection of upload signals, and multiple sub control panels located on other floors where system signals need to be monitored to control a certain exit signal.

4. Broadcast matrix

The broadcast matrix, as the name suggests, is a matrix that serves broadcasting. Its input signals mainly include satellite signals, signals from various studios, broadcast video recorder signals, output signals from the main control matrix, delayed broadcast signals, subtitle machine signals, as well as signals such as clocks and test cards. All these signals are commonly used signals for broadcasting, and the output signal of the main control matrix plays a role in expanding the broadcasting signal source. The broadcast matrix provides 3 channels of broadcast signals for each channel switching station, that is, 30 channels of signals for 10 broadcast channels of Shenzhen TV Station; Provide one main signal source and one backup signal source for each of the four delay devices. The backup signal and the delayed main signal are simultaneously sent to a 2x1 switch (the 2x1 switch plays an emergency switching role), which is then sent to various broadcast channels and loopback broadcast matrices for other purposes. The broadcast matrix also has 4 outputs to the main control matrix for signal exchange within the system.

The Application of Triple Auxiliary Matrix in the General Control System

In the TV control system, there are also some small auxiliary matrices. The size of auxiliary matrices is usually relatively small, such as 32 * 32, 32 * 16, 16 * 2, 16 * 4, etc. The auxiliary matrix has two main functions: firstly, it serves as an extension signal source for the main equipment, and secondly, it serves as a backup switching station for broadcasting.

The L-band matrix of the front 32X32 of the satellite receiver controlled by Shenzhen Television Station is a small auxiliary matrix that serves as an expansion signal source. Shenzhen TV Station has 15 satellite receivers under its overall control, and the satellite receives 26 signals. Through the L-band matrix, each receiver's reception selection signal can be extended to 26 channels.

The backup matrix for Shenzhen TV broadcasting switching stations is a small matrix of 16 × 2. All broadcast signals are simultaneously sent to the main switching station and backup matrix through video division, and the main and backup signals enter the broadcast channel through a 2x1 selector switch. When the main switching station fails, the 2x1 switch can be switched to select the backup matrix for playback. The broadcast ports of the main switching station and backup matrix are controlled synchronously by the same computer, so their output signals are switched synchronously. So as long as the 2x1 switch is switched in time, it will not affect the broadcast. The other output of the backup matrix can be used to pre monitor the broadcast signal, as shown in Figure 2.

Four Summary

From the above analysis, it can be seen that the overall control matrix system of Shenzhen Television Station is a circular structure, with me and you in it. The main control matrix is the center of the matrix system and can also serve as a backup for the input matrix and broadcast matrix. When any matrix malfunctions, the impact on the system is minimal, and the system can still operate normally. Therefore, the advantage of this structural design is its flexible use and guaranteed safety.

From Modern Television Technology