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The TV truck
A working vehicle that relays video
Television broadcasting vehicle is a kind of small "TV station" which has the characteristics of flexibility and wide range of activities. It can be far away from the television center for live recording, on-site editing work, and can immediately transmit the recorded program to the television center for live broadcast. In the late 1930s, France produced the first television broadcasting car. After decades of development, it has been widely adopted by all countries in the world.
- Chinese name
- The TV truck
- Foreign name
- outside broadcast van (OBV)
- Word language
- The TV truck
- note
- dian shi zhu R R
- exegesis
- A car carrying television relay equipment
catalogue
A car carrying television relay equipment. For live broadcast. With video recording, editing and other functions. The equipment can also be moved to the site for filming. The signal will be sent to the television station for broadcast by microwave equipment.
camera
Appearance of a large TV transfer car
With multiple TV signal input and more than one output, it can perform a multi-level screen stunt combination of two or more video signals for the director to switch selectively.
Microwave transmitting equipment
The signal output by the switcher is sent to the microwave transmitter on the commanding height through the cable, the microwave transmitter modulates the TV signal, and the microwave transmitting antenna directly transmits the wave to the microwave receiving equipment on the roof of the TV center, and the demodulated signal is sent to the TV broadcasting center.
Video recorder
The switching output signal is also sent to the VCR, which can record the program uninterrupted and perform various on-site editing tasks. The slow-motion control box equipped in the broadcast of sports programs can be remotely controlled by the video recorder for slow-motion replay.
synchro
Various timing and reference signals are generated to make the scanning system of each TV equipment work synchronously.
Sound equipment
Including microphone, mixer, recorder, audio jack board, audio distributor, etc. The live program sound is converted into an electrical signal by a microphone, and then sent to the relay car through the audio cable, and then sent to the video recorder, microwave transmitter and monitoring speaker through the audio jack board and audio distributor.
Monitoring system
Each camera is correspondingly equipped with a monitor in the car for the director to select the picture and the technician to monitor the technical quality.
Communication system
In the process of program production, in order to ensure the direction of the director and the coordination of the staff of various positions, special wired and wireless communication systems must be equipped.
Power supply air conditioning system Power supply system
It is generally powered by external mains and the generator in the car. The air conditioning system should ensure the stability of the working conditions and equipment in the car.
With the development of electronic technology and computer technology, the equipment of modern TV broadcasting vehicle is becoming more and more perfect, and its functions are increasing day by day. Cameras are increasingly controlled by microcomputers and fully automated, and multiple cameras can be adjusted at once through a centralized control unit. The application of these technologies has greatly enhanced the ability of television broadcasting vehicles to produce programs.
[1]
The study found that the general broadcasting vehicle internal space is small, not much work, making the HD broadcasting vehicle system more complex. Design principles can be divided into the following aspects:
① Design function perfection: In the design to have a global concept, to prepare for the future function upgrade, and to provide international universal signal, and can be multi-output.
② Technical advancement: The design system should be as far as possible in line with the future development of the television industry, to have a certain sense of advance. System equipment adopts stable advanced technology.
③ System operation reliability: the broadcast vehicle system should have good reliable performance, the design scheme must have perfect emergency operation measures, but also pay attention to the safety, reliability, networking of the system, and have automatic fault diagnosis function.
Control flexibility: the operating system should be simple and convenient, while easy to maintain and flexible signal deployment. By means of technology, the system integration can be reduced, and the safety and flexibility of the whole system signal scheduling can be improved.
The study found that the general TV broadcast truck adopts the following three types of car body structure: direct trailer car body structure, trailer car body structure and integrated car body structure, as shown in Table 1 below. Trailer car body structure, generally suitable for the station area and the number of equipment and other requirements are relatively high, large, large relay vehicle, this model has the characteristics of more production stations, large interior area, strong carrying capacity; Generally, the direct-mounted vehicle body structure is mostly suitable for medium-sized broadcasting vehicles, and its equipment installation and carrying capacity are relatively large, but the number of vehicle area and production station is relatively small. The unibody structure is often suitable for small relay vehicles that require strong flexibility.
In the design of the broadcast car, it is necessary to make full use of the limited space in the car, but also to fully consider the interaction and comfort of the human-machine interface can be modular integration of the production station in the car, and a large number of stations and equipment cabinets can be arranged reasonably in the limited space.
Audio system design
The development trend of modern digital television audio system in China is to use 5.1 channels, while the domestic digital high-definition TV broadcast trucks are using analog dual-channel audio signals. The direct transition from digital dual-channel audio to multi-channel audio is not easy, and usually involves upgrading an existing audio system to 6-channel audio.
The quality of HDTV program is based on the development of DVD level, so the use of 5.1 channel audio signal is the inevitable trend of the development of audio system of broadcast car. Sound recording is divided into 2, 4 and 8 channels. Of the eight channels, the seventh and eighth channels are free use channels, and the first to sixth channels.
The sampling frequency, frequency range, quantized bits, pre-weighted network and calibrated electrical parity standards of the audio system of the broadcast car are as follows:
Sampling frequency: First choose 48kHz, can also choose 32kHz or 44.1kHz. The sampling frequency of the low-frequency enhanced sound is 1/96 of the sampling frequency of the main sound channel.
Frequency range: the channel frequency range of low-frequency enhanced sound is 15Hz ~ 120Hz, and the frequency range of other channels is 20Hz ~ 20kHz;
Quantization bit: The encoding method generally used is PCM audio, preferably 20bt linear quantization, in addition, 16, 18 and 24 bt linear quantization can also be selected;
Calibration level: GY/T 192-2003 "Full level of digital audio equipment";
Pre-emphasis network: Pre-emphasis network cannot be used.
(2) Audio system design
The standard design of the HD broadcast system is a 5.1 channel audio system, which requires the use of multiple monitors
Digital mixing console
. In the audio system design: First, the audio signal is recorded in digital format. Both audio recording digital recorders and HD recording digital video recorders usually use the AES/EBU digital audio interface standard. The interface is 48KHz sampling and 20/24bt quantization. Secondly, the monitoring system is also much more complex than the usual system, and it is necessary to use a 6-channel full-band audio monitoring system.
Compared to the traditional design, the 5.1 audio design system concept has many advantages:
The flexibility of the system is large. The audio matrix adopts a modular structure, and these modules are designed for digital audio systems and can be directly connected to various audio devices, avoiding conversion between different interfaces. The tuning system has more bus bars, the control panel is flexible, and the whole system can be flexibly configured according to the work needs.
Audio system size is unlimited. The audio matrix should have 192x192 (3097x3097) input and output functions, and the tuning system should have multi-DSP channel performance, in addition to a clear structure and easy connection.
The reliability of the system is high, and the system security of this design scheme is promoted to a new level. All modules can be hot-swappable and can be backed up redundantly, as well as the motherboard and control unit as needed, with a fully backed up dual-star topology for truly barrier-free operation from component to system.
The signal strength of the system is high and is not limited by the transmission distance. Because the entire system structure is distributed, the audio system can receive signals at the signal station nearest to the system, and then achieve long-distance connection through optical fiber, which reduces the electromagnetic interference in transmission and grounding noise between different places.
Video system design
(1) Video standards
According to the State Administration of Radio, Film and Television HDTV standard:
1080/60i indicates that the number of effective scanning lines is 1080, and the interlaced scanning field frequency is 60Hz; 720/60p indicates that the number of effective scanning lines is 720 lines, and the progressive scanning frame rate is 60Hz.
High definition digital TV uses SMPTE 292M standard, the interface adopts serial digital component to transmit digital component signal and its embedded multi-channel digital audio signal, the sampling frequency is 74.25MHz, the quantization level is 10 bits, and the bit rate is 1485 Mbps.
(2) Synchronous system
The synchronization signal of high definition video system adopts three level synchronization signal. In order to achieve accurate synchronous separation with minimum oscillation, the midpoint of the timing edge should be placed in the middle of the video blanking level, so that the system can maintain the reliability and accuracy of timing in the multi-noise environment.
The design scheme of master/standby switchover is adopted, using two synchronizers and an automatic synchronizer, when one synchronizer fails and cannot provide synchronization signal, the other synchronizer will automatically start, so as to ensure that the system can continue to provide synchronization signal.
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