With the rapid development of the broadcasting industry, people's demand for broadcasting content is also increasing. After several years of effort, Dalian Radio has expanded from one news channel to five channels today. The previous simple transmission method from live broadcast rooms to microwave transmission has been limited in practical work. How to scientifically and effectively transmit programs from 5 or even more channels, and establish a safe, reliable, high performance, and high-quality broadcasting technology system? Our station is investigating the work situation of external stations and, combined with the actual situation of our station, has introduced the matrix system widely used abroad. Below is an introduction to the matrix design and actual usage used by our station, for reference by our sister stations.

The main control system is the core of the broadcasting transmission system, and all live and broadcast signals of programs are collected in the main control room. As the core of the overall control system, the program exchange matrix plays an irreplaceable role in achieving automatic program broadcasting and mutual conversion. Our station is currently using a 44 × 56 digital matrix developed by Student Company. This product adopts a modular design and a front plug-in board structure system. If there is a problem with the system, only the faulty module will be replaced (all inputs and outputs in the system, including the power board, support hot plug-in boards), without causing the entire matrix system to be completely paralyzed, and it is maintainable. Another characteristic of modular design is anti-interference. The input and output boards are independently wired, greatly reducing interference between analog and digital. Good safety performance brings convenience to system maintenance.

The matrix adopts dual power supplies, with mutual hot backup. The working voltage of the power board is 15V, with 5V as one group, totaling four groups. When any two sets of power boards fail, the other two sets of power boards automatically bear the full power of the matrix without manual intervention, and any two of the four sets of power boards can independently support system operation. There are indicator lights on the panel that display the various voltage supply status of each power board. The Student D19m 44 × 56 matrix is a synchronization matrix that operates at a fixed sampling frequency. It can use both internal and external synchronization, and requires high system accuracy. The matrix has timed automatic switching and manual switching modes. The computer switching control software completes the allocation of signals from input to output (the matrix has a good human-machine interface). The fully Chinese control software switching interface matched with the matrix more intuitively reflects the matrix input and output situation, making it easy to operate.

Actual usage:

1. Number matrix

Our station has 5 sets of self-produced programs signal sources to relay satellite signals from China National Radio and China Radio International, a total of 7 sets of programs. Considering the peripheral equipment that must be connected to the matrix, such as CD pad music machine, six tone alarm timing, etc., and the possibility of future expansion, we select a 44 × 56 composite/mono channel audio digital matrix, that is, three digital and five analog modules, a total of 44 inputs (each module has four outputs/inputs, each digital module inputs a stereo, and each analog module inputs a mono), and six digital and two analog modules have a total of 56 outputs. The numbers are uniformly in AES/EBU format. Except for the 5 digital input ports occupied by the output signal of the live broadcast room, the other 7 digital input ports are respectively connected to the quotation, speech repetition, CD player, and digital recording studio. This is to consider that if any live broadcast room encounters major problems and cannot be used, it can be used as a temporary live broadcast room. Pre arrange broadcasting equipment such as mixing consoles, CD players, MD players, audio workstations, etc. in these rooms, which have studio functions in both usage and interior design requirements. Usually, quotes and language repetitions are used for recording and synthesizing programs, which can be recorded into audio workstations, booths, MDs, etc., providing a richer signal source for broadcasting. The broadcast signal and the six ring alarm are analog signals that are input from the matrix analog block, converted into digital signals through analog-to-digital conversion, and sent to the required live broadcast rooms. Because the main signal of the mixing console in the live broadcast room is required to be a digital signal. It is worth mentioning that the analog matrix used in the past, despite losing its main role in the digitization of broadcast signals today, still plays an indispensable role in broadcast signal transmission through clever use. For example, we connect the input and output of a digital matrix with the output and input of an analog matrix. This way, the analog matrix can not only serve as a backup for the digital matrix, but also as a pathway for providing signals to each other, for sharing broadcast signal resources. For example, before the broadcast of the CCTV news at 6:30 a.m., the signal "digital matrix returned to the live broadcast room", which is usually the main broadcast signal, was suddenly interrupted. In order to ensure the normal broadcast, there are two emergency handling methods. One is the backup broadcast signal sent to the live broadcast room by the analog matrix in advance, which can deal with similar emergencies in a timely and rapid manner, fully reflecting the traditional backup role of the analog matrix. Another method, when time permits, is to transfer the broadcast signal of the analog matrix through the path connected to the digital matrix to the "digital matrix return live broadcast room" along the way, and turn the backup analog signal into the main digital signal. Although the latter method is more cumbersome than the former method, the flexible signal allocation method of the latter has practical application value for analogy.

The digital matrix of 44 × 56 composite/mono audio can not only fully meet the existing broadcasting routines, but also retain a certain margin in the design for expansion, which only requires some minor adjustments.

2. Alarm system

The output signal of the digital matrix is divided into four channels through the audio processor (specific allocation depends on the actual needs of each unit). All the signals are sent to the optical transmitter as the main signal for frequency modulation broadcasting at the transmitting station. The other three channels are respectively sent to: meter bridge - the output signal level of each live broadcast room is clear at a glance, slow recording - the computer records the audio signal for convenient future viewing, and the alarm system. The system consists of an AM-32 audio monitor and an AL-32 audio alarm. The AM-32 audio monitor locks the monitored matrix output signal and the corresponding radio received signal, and sets them within a dynamic range that meets the broadcast output standard. When the signal exceeds or does not meet the standard, the AL-32 alarm sends an alarm signal to prompt the operator to take necessary emergency measures. The AM-32 monitor can also monitor the input signal of the matrix, and the computer can switch the input signal of the matrix to the one used for monitoring. The use of alarm systems not only helps to solve the problem of untimely monitoring, but also helps check-in personnel reduce work intensity and fatigue when monitoring multiple signals, which is beneficial for work. The signal alarm system helps to monitor and monitor broadcast signals, but regular patrols and inspections are still important for ensuring the quality of broadcast signals.

3. Emergency system

In addition to the analog matrix mentioned in the above matrix system as an emergency facility, we have also added a jumper board as another emergency measure. When the matrix fails, the audio channel of the matrix cannot transmit signals normally, or the control computer cannot switch normally, the emergency system can discard the matrix and output directly with the jumper. The input and output of the jumper board should correspond one-to-one, with the upper wire for signal acquisition and the lower wire for signal transmission. The analog board and digital board cannot jump to each other.

Excerpt: Yima Lion Network Author: Mou Dafen Dalian Radio Broadcasting Department