introduction
Digital cinema refers to the production, storage, and transmission of digital media and equipment through physical media such as satellite, optical fiber, magnetic disk, optical disk, etc., to restore digital signals to video and sound in accordance with film technology standards, and to screen movies on the screen. works. Compared with traditional movies, it has the characteristics of clear picture, high stability, cost saving and environmental protection. From an international point of view, after the initial stage of exploration, digital film technology has been relatively mature, and the creators have gradually transformed from the past using digital special effects into a performance method that integrates them with traditional filming and traditional stunts. In China, digital cinema has undergone the process of introduction, digestion, imitation and innovation. In order to encourage and promote the development of digital cinema in China, the state has invested a large amount of money to build more than 100 digital cinemas across the country. According to China's national conditions, the first is to popularize and promote the development of digital cinema in our community and rural areas. Therefore, a large number of low-end configuration of mobile digital cinema projection equipment is needed.
DaVinci technology is a connotation-rich technology complex. It is a collection of DSP-based system solution components tailored for TI's digital multimedia applications. It simplifies design and accelerates product innovation for multimedia device developers. Integrated processors, software and tools. TI has designed a system framework for audio and video codec multimedia applications on the DaVinci platform, providing a rich system programming interface (SPI), application programming interface (API), and video, image, voice, and audio. More than a thousand kinds of streaming media algorithm components. Application system developers can easily design high-availability and high-reliability digital video products by simply packaging them into a running package.
In order to meet the actual needs of China, this paper puts forward the scheme of developing digital cinema projection system and its specific implementation method based on the Da Vinci software hardware platform based on the Da Vinci system hardware platform. This program helps to shorten the product development cycle and capture the market faster.
1 Hardware Design The digital film projection system is mainly realized by the digital multimedia processor TMS320DM6446. The TMS320DM6446 is TI's highly integrated video processing chip, which is known as the DaVinci Digital Media System-on-Chip (DMSoC). Figure 1 is a block diagram of the functional structure of the TMS320DM6446.
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As shown in FIG. 1, the DMSoC includes an ARM subsystem, a DSP subsystem, a video processing subsystem (VPSS), a system control module, a power management module, an external storage interface, a peripheral control module, and a switching center resource (SCR). Among them, the ARM subsystem is mainly responsible for the overall configuration and module function control of the TMS320DM6446 system, as well as calling video algorithms. The DSP subsystem operating at nearly 600 MHz is responsible for the execution of the video algorithm, with a maximum processing power of 4800 MIPS, greatly enhancing the decoding capabilities of audio and video. The video processing subsystem includes a video front end input interface (VPFE) and a video end output interface (VPBE). The video front end input interface is used to capture video signals, and the video end output interface outputs images to the OSD for display.
The structural block diagram of this system is shown in Figure 2. The system externally connects 64 MB of NAND Flash through the asynchronous external memory interface (EMIF) to store boot code and data to boot the ARM Linux operating system. The ATA controller interface is connected to an external 160 GB 2.5 in ATA hard disk, which is mainly used for storage of file systems, applications and a large number of digital movie files of Linux systems. Since the ATA hard disk outputs a 3.3 V voltage signal, and the TMS320DM6446 hard disk controller outputs a voltage signal of 1.8 V, in order to make the hard disk and the main CPU connect normally, a voltage conversion chip is required to ensure the normal operation of the hard disk. In addition, in order to facilitate the change of video programs and easy to test, the system also expands the 2 GB SD card and USB2.0 interface through the MMC/SD memory card interface. The TMS320DM6446's 32-bit DDR2 controller is used to buffer 256 MB DDR2 SDRAM buffered video input graphics data, which acts as a buffer for the OSD to store ARM and DSP code.
The system's video front-end input interface (VPFE) supports composite video (CVBS) input and S-terminal input. The video end output interface VPBE supports analog video output, including composite video (CVB-S) output, S-terminal output, component video output (YPbPr) and VGA output. At the same time, it supports digital video output (DVI). The video decoding module uses TI's high-quality video decoding chip TV-P5158 to convert common baseband analog video formats into digital video formats. The input video data is converted into a 10-bit YUV4:2:2 format by the TVP5158 video decoding chip, and then sent to the video front end for processing, and the processed data is processed by the video end and saved to the hard disk. The audio decoding module uses TI's low-power stereo decoding chip TLV320AIC33. Considering that the system needs to connect multiple modules, the I2C protocol supported by the AIC33 serial bus control is used here, and the audio interface of the DSP is connected through the I2C interface. In addition, in order to monitor the startup of the hardware platform, the UART peripheral controller integrated with the TMS320DM6446 is used to extend the UART universal asynchronous serial port, and RS232 is configured for the console at system startup.
2 Software Design The software design of the digital cinema projection system is mainly done in the Linux system environment, using the Da Vinci software framework structure. By packaging audio and video algorithms that conform to digital media standards (xDM) into Codec Server (code server) managed by CodecEngine, the ARM-side application can invoke audio and video algorithms integrated into Codec Server. Decode audio, video, and voice data from the Linux file system and output it to the Linux device driver on the TMS320DM6446 that controls video and voice peripherals.
2.1 Da Vinci Software Development Method When developing the system software, the software development process is shown in Figure 3.
The specific steps of software development are as follows:
1DSP side, in the CCS3.3 development environment introduced by TI, the audio and video decoding algorithm is modified to conform to the digital media standard (xDM) form, and compile and generate an algorithm library file*. Lib (equivalent to *.a64P in Linux environment, modify the file suffix directly in the Linux environment).
2 Generate an executable program running on the DSP*. x64P (ie.out file), which is Codec Server. The system's Codec Server integrates MPEG-2, MPEG-4, and H. 264, AAC, MP3, G. 71l various forms of audio and video decoders.
3 According to the name of Codec Server and the specific audio and video decoding algorithm included in it, create Codec Engine configuration file *.cfg, including different configuration and name of Engine, Codec included in each Engine and each Codec running in ARM or DSP side and so on. For example, at. In the cfg file, you can modify the relevant statements of the Codec module and reference the Codec module as needed. The statements for obtaining different modules are as follows; 
Code modules can be developed on their own, or they can take advantage of third-party software technologies. Any xDM-compatible algorithm can be integrated into Codec Server. This avoids the duplication of development and reduces the difficulty of development.
4 will collect different audio and video Codec package, Codec Server and Engine configuration file *. The cfg and the application are compiled and linked to finally generate an ARM-side executable file.
2.2 Da Vinci Middle Frame Codec Engine
The Codec Engine is the middle layer between applications and code servers and is a key component in simplifying digital product development with DaVinci technology. It provides a VISA interface for applications that can easily call xDM-compliant algorithm components using the API provided by Codec Engine without having to worry about complex video, image, voice, and speech processing algorithms (VISA).
2.3 ARM-side decoding application design The application of this system is implemented in the Linux system environment, using the API provided by the Codec Engine of DaVinci technology. The application runs on the ARM side of the TMS320DM6446 dual-core processor, decodes the audio, video, and voice data stored in the hard disk, and outputs it through the video end output interface (VPBE) for real-time display on the OSD.
The process of decoding the thread is shown in Figure 4.
The application mainly includes five POSIX threads: the main thread (control thread), the video thread, the display thread, the voice thread, and the audio thread. As can be seen from Figure 4, the video, voice, and audio threads are generated before the main thread becomes the control thread. The display thread is generated by the video thread. "MSP430+IR" is used to receive commands entered by the user. The video thread can only be created when a video file is provided on the command line. At the same time, since audio and voice require the same peripherals (AIC33), audio and voice files cannot be decoded at the same time. In addition, all threads are preemptive, priority-based timing (SCHED_FIFO), where the display thread has the highest priority, followed by the video thread, which has the lowest priority. The initialization of the thread is synchronized by the Rendezvous utility module. This module uses POSIX conditions to synchronize thread initialization. The Rendezvous object is notified after each thread performs its initialization. After all the threads have finished initializing, they are unlocked at the same time and the main loop is executed.
3 Test Results The software development of this system is carried out under the Linux operating system on the virtual machine. The version of the Linux operating system is Monta Vista Linux Professional Edition v4. Before testing, connect the hardware platform to the host through the switch and configure the NFS (Network File System) service so that the development board and the host can access each other. At the same time, in the Windows environment of the host, the development board Connect to the host with a serial cable, set up the HyperTerminal, monitor the startup of the hardware system through the HyperTerminal, and set the command parameters.
During the test, the decoding command is input in the HyperTerminal. The hardware system parses the input command through the MSP430, reads the audio and video data stored in the HDD (hard disk), and displays the decoded video online using the OSD. Figures 5 to 7 are for MPEG-2, MPEG-4, and H. Decoded image of 264 audio and video.
Conclusion This paper combines Da Vinci digital multimedia technology to propose a hardware solution and software design method for digital cinema projection system. DaVinci's support for high-level Linux, standardized APIs, and product-based underlying drivers greatly reduce the complexity of designing digital video systems and shorten the product development cycle. Tests show that the designed digital cinema projection system supports high-definition playback of digital movies in multiple formats with high stability and high reliability. The design can also be used for the development of other digital products such as IP set-top boxes, network cameras, medical image processing, video conferencing, and more.
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