TV relay vehicle is a small vehicle mounted "TV station" with the characteristics of mobility, flexibility and large range of activities.It can record and edit live programs far away from the TV center, and transmit recorded programs to the TV center for live broadcast.In the late 1930s, France produced the first television relay vehicle.After decades of development, it has been widely adopted by all countries in the world.
A car carrying television equipment.It is used for live broadcast.It has video recording, editing and other functions.The equipment can also be moved to the site for shooting.The signal will be sent to TV station for broadcast by microwave equipment.
equipment
video camera
Appearance of large TV relay vehicle
The camera on the vehicle is equipped according to different production requirements.According to the director's intention, the camera is placed in different positions on the scene.The TV signal output by the camera is sent to the rebroadcast vehicle through the cable.
It has multiple TV signal inputs and more than one output, and can perform multi-level stunt combination on two or more video signals for directors to selectively switch.
Microwave transmitting equipment
The signal output by the switcher is sent to the microwave transmitter installed on the commanding point through the cable. After the microwave transmitter modulates the TV signal, the microwave transmitting antenna directly transmits the radio wave to the microwave receiving equipment on the top of the TV center building, and the demodulated signal is sent to the TV broadcast center.
video recorder
The switching output signal is also sent to the video recorder, which can record programs uninterruptedly and perform various on-site editing work.The slow motion control box equipped in the relay of sports programs can remotely control the video recorder for slow motion replay.
Synchronizer
Generate various timing and reference signals to make the scanning system of each TV device work synchronously.
hi-fi equipment
Including microphone, mixer, recorder, audio jack board, audio distributor, etc.The live program sound is converted into an electrical signal from a microphone, and then sent to the rebroadcasting vehicle through an audio cable, and then sent to the video recorder, microwave transmitter and monitoring speaker through an audio jack board and an audio distributor.
Monitoring system
Each camera is correspondingly equipped with a monitor on the vehicle for directors to select pictures and technicians to monitor technical quality.
Call system
In the process of program production, special wired and wireless communication systems must be equipped to ensure the coordination between the director and the staff at all posts.
Power supply Air conditioning system Power supply system
Generally, the power is supplied by the external mains and the built-in generator.The air conditioning system shall ensure the stability of working conditions and equipment in the vehicle.
development
With the development of electronic technology and computer technology, the equipment and functions of modern TV relay vehicles are increasingly improved.More and more cameras are controlled by microcomputer and adjusted automatically, and multiple cameras can be adjusted at one time through a centralized control unit.The application of these technologies has greatly enhanced the ability of TV relay vehicles to produce programs.[1]
Design
Announce
edit
Design principles
It is found that the internal space of the general broadcast vehicle is narrow and there are not many working positions, which makes the HD broadcast vehicle system more complex.The design principles can be divided into the following aspects:
① Completeness of design function: in the design, we should have a holistic concept, prepare for future function upgrading, and provide international universal signals, which can be multiplexed.
② Advanced technology: the design system should be as consistent as possible with the future development of television industry, and there should be a certain sense of advance.The system equipment adopts stable and advanced technology.
③ System operation reliability: the relay vehicle system must have good reliability, the design scheme must have perfect emergency operation measures, and pay attention to the system's safety, reliability, networking, and automatic fault diagnosis function.
④ Control flexibility: the operating system should be simple and convenient, and the maintenance should be convenient and the signal allocation should be flexible.Reduce system integration through technical means, and improve the security and flexibility of signal dispatching of the whole system.
overall design
It is found that the following three types of car body structures are adopted for general TV relay vehicles: direct mounted car body structure, towed car body structure and integrated car body structure, as shown in Table 1 below.The trailer type car body structure is generally applicable to super large and large broadcast vehicles that have high requirements on the area of stations and the number of equipment. This model has the characteristics of many production stations, large interior area and strong bearing capacity;The general direct hanging car body structure is mostly suitable for medium-sized broadcast vehicles, and its equipment installation and bearing capacity are also relatively large, but the car interior area and the number of production stations are relatively small compared with the trailer type car body structure;The integrated body structure is often suitable for small broadcast vehicles that need strong flexibility.
In the design of the rebroadcast vehicle, the limited space in the vehicle shall be fully utilized, and the interaction and comfort of the human-computer interface shall be fully considered. The production stations in the vehicle can be modularized and integrated, and a large number of stations and equipment cabinets can be reasonably arranged in the limited space.
The development trend of modern digital TV audio system in China is to use 5.1 channels, while domestic digital high-definition TV relay vehicles use analog dual channel audio signals.It is not easy to directly transition from digital dual channel audio to multi-channel audio. Usually, the existing audio system is upgraded to 6-channel audio.
The quality of HD TV program is based on the development of DVD level, so the adoption of 5.1 channel audio signal is the inevitable trend of the development of the audio system of the rebroadster.Sound recording is divided into 2 channels, 4 channels and 8 channels.Among the eight channels, the seventh and eighth channels are free use channels, and the first to sixth channels.
The sampling frequency, frequency range, quantization bit, pre emphasis network, calibration level and other standards of the audio system of the relay vehicle are as follows:
Sampling frequency: 48kHz, 32kHz or 44.1kHz can be selected first.The sampling frequency of low-frequency enhanced sound is 1/96 of the sampling frequency of the main 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: PCM audio is generally used as the encoding method, and 20 bt linear quantization is preferred. In addition, 16, 18 and 24 bt linear quantization can also be used;
Calibration level: GY/T 192-2003 Full Scale Level of Digital Audio Equipment;
Pre emphasis network: pre emphasis network cannot be used.
(2) Audio System Design
The standard design of the HD rebroadcast system is a 5.1 channel audio system, which requires the use of multiple monitorsdigital mixer 。When designing the audio system: First, record the audio signal in digital format.AES/EBU digital audio interface standard is usually used for both digital recorders for audio recording and digital video recorders for high-definition recording.The interface is 48KHz sampling and 20/24bt quantization.Secondly, the monitoring system is also much more complex than the usual system, and a 6-channel full band audio monitoring system must be used.
Compared with the traditional design, the 5.1 audio design system has many advantages:
The system is flexible.The audio matrix adopts a modular structure. These modules are specially designed for digital audio systems, and can be directly connected to various audio devices to avoid conversion between different interfaces.There are many bus bars in the tuning system, and the control panel can be flexibly combined. The whole system can be flexibly configured according to the work needs.
The scale of audio system is unlimited.The audio matrix shall have 192x192 (3097x3097) channel input and output functions, and its tuning system shall have the performance of multiple DSP channels. In addition, it shall have clear structure and simple connection.
The reliability of the system is high, and the security of the system in this design scheme is upgraded to a new level.All modules can be hot pluggable and redundant backup can be performed, and the mainboard and control unit can also be backed up as required. The fully backed up dual star topology is adopted to realize the truly barrier free operation from components to the system.
The system signal strength is high and is not limited by the transmission distance.Since the whole system structure is distributed, the audio system can receive signals at the signal station nearest to the system, and then realize remote 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 HDTV standard of SARFT:
1080/60i means the number of effective scanning lines is 1080, and the interlaced scanning field frequency is 60Hz;720/60P means that the number of effective scanning lines is 720, and the progressive scanning frame rate is 60Hz.
The high-definition digital TV meets the SMPTE 292M standard. The interface uses serial digital components to transmit digital component signals and their embedded multi-channel digital audio signals. The sampling frequency is 74.25 MHz, the quantization level is 10 bits, and the code 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 synchronization 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 a multi noise environment.
The design scheme of main and standby switchover is adopted. Two synchronizers and one automatic synchronous switcher are used. When one synchronizer fails and cannot provide synchronous signal, the other synchronizer is automatically started, so that the system can continue to provide synchronous signal.[2]
