1. In the production of TV studios and OB trucks, the Tally system is an auxiliary system when the video transmission system is working. It prompts the cameraman, host, director, producer and technician through the color display of the indicator light or characters. It is also known as the av source indication system and plays a role in coordinating the cooperation of the staff in each position and be clear of working status in a timely manner during the program production process. No matter it is in the studio or the OB vehicle system, the tally system is a very important component.
In ESP (Electronic Studio Production) and EFP (Electronic Field Production) systems, the Tally lamp can be seen inside and on top of the camera's viewfinder. The red Tally light is used to indicate which camera signal is being switched out. It helps the broadcaster to face the camera and ensure the correct line of sight. It also reminds the cameraman that the camera signal has been cut out by the guide. It cannot be adjusted at this time. At the same time, there will be Tally instructions on the monitoring wall and camera control panel in the production area to remind the production staff and technicians which signal is currently cut out. Some Tally lights will also display yellow, indicating that the camera signal has been preselected and will be cut immediately. When the director directs the switching effects such as wipe or superimpose, the red Tally lights of the two cameras will light up at the same time. At this time, the camera operator needs to operate according to the intent of the director.
2. Development of Tally system
In the earliest Tally system, above each monitor on the monitoring wall in the production area, there was a prompt board with plexiglass lettering illuminated by backlight. The character content of the prompt board was fixed, that is, the monitor displayed Source name. The backlight is turned on or off by an external on-off trigger signal to achieve Tally prompting. This Tally system is a monochrome display (often off / red light), the disadvantage is that once the source name display needs to be changed, the prompt board must be replaced. A
Later, a LED light-emitting dot matrix with character settings was developed. The character content of this Tally lamp can be modified by software. Its working state is still triggered by an external on-off signal, and the lighting method becomes two-color. The selected signal source shows green, and the signal cut by PGM shows red. A
With the emergence of UMD character display module, the Tally system has become more complicated and can display intelligent dynamic source names. UMD (Under Monitor Display) is a display module for dynamically indicating the name and status of the signal source on the monitoring screen wall of TV studios and OB vehicles. In use, it can dynamically display the name of the signal source according to the change of the current matrix intersection And status. The signal it receives is a serial digital signal, and the displayed content can be changed in real time, with great flexibility. This Tally system has a three-color display, unselected signal sources display green, PVW preselected signals display yellow, and PGM cut-out signals display red.
3. Tally classification and principle
According to the working principle, Tally display can be divided into parallel Tally and serial Tally. Parallel Tally means that the Tally controller uses the Tally control signal to drive the CCU of the camera and other devices that need to be controlled. This system is generally directly controlled by the GPO of the switcher and can only control the red and green indicator lights. Serial Tally is to read and transmit Tally data to related equipment through serial data protocol, or convert to parallel Tally drive through serial-to-parallel converter. Serial Tally can complete very complicated control. In addition to the light indication, it can also control the UMD character display content, color and size. At the same time, the light indication and UMD can be dispatched on the monitoring wall together with the bound signal source. A
Serial Tally can also use different control protocols. At present, TSL protocol is the most commonly used Tally and source name control protocol for broadcast TV systems, and has been supported by most TV equipment manufacturers. The centralized control method using the TSL protocol is to use a computer to set up the Tally controller, connect to the switcher, matrix and monitoring system through different serial protocols, translate and exchange data, so that the decentralized system becomes a centralized Controlled system.
4. Tally system as an important part of the OB truck, with the development of network technology, it is also constantly moving towards digitalization, networking and intelligence. Nowadays, the application of Tally signals is no longer a simple broadcast prompt function in the traditional sense. The emergence of serial Tally provides us with rich signal source status information and provides a powerful guarantee for the intelligent control of the system. Users can develop and apply various functions to the Tally signal according to their own requirements for the system, so that they can play a greater role in the OB vehicle system.