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Abstract: This paper elaborates the DPTV system based on CTV100 platform from two aspects of hardware and software, and gives the overall design block diagram and design flow chart. This project uses STMicroelectronics' (ST) CTV100 solution to achieve efficient digital domain processing of traditional analog TV signals, significantly improving the image quality of TV pictures; and by using OS20 embedded operating system based on 32bit CPU A variety of functions not possible with traditional analog TV.Keywords: digital processing TV ; embedded operating system; state machine ; upconversion
DPTV, that is, digital processing TV, which performs analog-to-digital conversion of the received analog full-TV signal under the analog broadcast television transmission system, then stores, processes and transmits the digital signal, and finally passes through the D/A conversion circuit. Reconverted to an analog signal and displayed a color TV receiver that is broadcast. The biggest difference between DPTV and traditional analog TV is that it will receive the analog full TV signal and then output it through the digital image of the internal digital chip of the TV. As a result, its overall performance has been greatly improved compared to traditional analog TV. The system introduced in this paper is two-chip scheme, the hardware circuit design is simple; the software system adopts the idea of ​​layered design and modular design, with clear hierarchy and reasonable structure; the project adopts PEG tool specially developed for embedded system graphical interface, making this The menus and games developed by the system have a good visual effect and are a good solution for DPTV TV.
Hardware platform construction
The overall design block diagram and the overall design block diagram of the hardware platform are shown in Figure 1. The STV2310 is a high-quality video processing front-end chip for processing standard analog signals and converting them to digital signal outputs. The signals it can handle include CSCBS TV signals in NTSC/PAL/SECAM format, as well as analog RGB and YCrCb signals.
Figure 1 overall design block diagram
The STV3500 is a low-cost, highly integrated processor chip dedicated to the 100Hz TV solution, which gives the STV2310 a strong support. It includes internal line and field multipliers, an interface for controlling peripherals in the machine, and a 32-bit ST20 series CPU core, as well as an internal OSD generator that can display text and images. It can receive composite standard video decoding chip (STV2310). The transmitted video stream conforms to the ITU2RBT.601/656 standard.
The display processing module is composed of two chips, STV9211 and STV9118. The STV9211 is used to pre-amplify the RGB signals output by the STV3500 and provide adjustments for brightness, contrast, drive level, and black level. The STV9118 is used to implement all functions related to line deflection. These functions are implemented by setting the value of the relevant register. The input signal switching module is composed of a CD4052 chip, which mainly performs switching between various video input signals.
System Workflow The entire DPTV system is roughly divided into three parts, a bottom plate portion, a digital plate portion, and a display portion. The bottom plate part and the display part are the same as the traditional analog TV, and the digital board part of the system is not available in the traditional analog TV, and is the most critical part of the whole system.
The tuning of the high frequency signal is selected via the bottom plate portion tuner module, and the television signal is sent to the television receiver. After mixing, the intermediate frequency TV signal is sent to the intermediate frequency processing chip for processing, and the entire television signal and the audio signal extracted therefrom are respectively sent to the respective decoding chips for processing. The full TV signal is transmitted to the STV2310 on the digital board. The A/D conversion module STV2310 receives various analog TV signals from the TV backplane, converts them into digital signals, and sends them to the bright color separation module of the STV2310. The performance of the digital comb filter used by the STV2310 is far superior to the traditional analog. The analog bright color separation module of the TV, the crosstalk between the bright and color signals can be minimized, and the image quality is greatly improved. Thereafter, the luminance and chrominance signals are processed separately, recombined, and output in a 4:2:2 YCrCb format. Its output will be sent to the central processor chip STV3500.
In the STV3500, the input video data stream is first converted to the desired display format. The up-conversion technology is to improve the large-area flicker caused by the low field frequency of the traditional analog TV by multiplying the field frequency (50Hz to 100Hz), so that the image is more stable and smooth. This chip can generate the correct video display sequence according to the up-conversion mode. After processing through the image enhancement techniques in the chip, the TV menu, cursor and background will be superimposed on the TV image. Finally, the overlay signal will be sent to the video display module connected to the STV3500. After some necessary processing is performed on the display effect of the image in the video display module, the image will be sent to the display portion of the DPTV system in RGB format for display.
Software system implementation
Software Architecture The software system of this project adopts hierarchical structure design. The whole system can be divided into four levels, namely system layer, driver layer, service layer, and application layer. With this structure, the entire system is highly flexible, easy to transplant, and easy to understand and develop.
1) System layer. Used to provide operating system function interfaces for other three layers. The system uses the OS20 real-time multitasking embedded operating system, which provides an operating system abstraction layer (OSAL) that enables the other layers to be completely independent of the operating system.
2) Driver layer. A layer that directly interacts with the hardware. This layer adopts a modular design concept. Different chip or chip functions are divided into different modules, and each driver layer module provides an interface for the upper layer to access the chip or chip function.
3) Service layer. Located above the driver layer, this layer integrates the driver layer module functionality to provide an interface to its upper application layer.
4) Application layer. It is the core part of the entire software system, the user menu is generated at this level, and the management of the entire software system is also implemented at this level.
The software flow program flow chart is shown in Figure 2.
Figure 2 DPTV software flow chart
After the initialization of the operating system kernel is completed, the system prerequisites such as interrupts, handles, and semaphores are then initialized, and the entire operating system is fully operational. The system then creates its main task, and all other subtasks are created in this main task. After the initialization of each driver layer module and service layer module is completed, according to the division of the system module, the operating system creates multiple subtasks, and subsequent control for different modules is performed by the tasks corresponding to the modules. After that, the main task enters an infinite loop waiting for the arrival of an external message. The Peg task responsible for managing the OSD menu also enters an infinite loop waiting for an external message to be triggered. The state machine is used to implement the processing of a large number of different messages. When the user needs to turn off the TV, the operating system first deletes each subtask, releases the semaphore, handle and other resources and ends the main task. At this time, the system only runs the most basic functions of the operating system to wait for the user to activate the entire system again.
The state machine mechanism is the core of the entire software system. When the user presses the remote control or the front panel button of the fuselage, the message is sent to the main state machine of the loop waiting message. The main state machine analyzes and processes the message, and operates the corresponding chip on the bottom layer through the driver layer module to change the state of the TV set according to the user's request, and simultaneously transmits a message to the Peg task in the user interface layer through the ap_mmi_KeyStrike() function, requesting a menu change. The Peg state machine accepts messages from the main state machine and changes the user interface as required. If necessary, the Peg state machine can also request hardware operations from the underlying layer via the callback function ap_cmd_PegCallBack().
System performance analysis
Compared with traditional analog TV and other DPTVs, this system uses a number of unique technologies to make the quality of TV pictures significantly improved. The main features of this system include:
1) The 32-bit 100MHz CPU embedded in the STV3500. This greatly improves the data processing capability of the system and provides a guarantee for high-quality picture quality.
2) Unique upconversion algorithm. The algorithm provides up-conversion of multiple modes (AA*B*B, ABAB, Proscan, and interpolated modes) to suit different applications and input signal types. Depending on the source of the signal, the CPU automatically selects the optimized multiplier mode to process the data.
3) Unique OSD generator and image synthesizer. Used for overlaying each layer, the embedded 2D acceleration engine speeds up the display of images; supports 256-color display, supports 256-level transparency settings, and makes the system's menus and game colors more rich.
4) Image enhancement module. Within the STV3500, image quality is improved through various digital domain processing techniques. These technologies mainly include: chrominance enhancement, 3D instantaneous noise reduction, motion estimation, contrast enhancement, and so on.
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