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A high definition media information release terminal design

In Electronic Infomation Category: A | on April 20,2011

1 Introduction

With the continuous development of communication technology, the increasing popularity of high-definition applications, the traditional multimedia information terminals can not meet the demand for high-definition media playback. There is existing technology systems for complex, high cost, inadequate and LP2950CZ-3.3 datasheet and poor playback quality, this paper presents a high-definition media information release terminal design program, which uses an embedded platform architecture and LP2950CZ-3.3 price and hardware decoding technology to support multiple audio, video and LP2950CZ-3.3 suppliers and pictures format, enabling video, audio, pictures, and scrolling marquee combination of multimedia information such as playback, playback quality can be achieved excellence in high-definition TV quality. HD media distribution system as a terminal node, the system in a remote central control system management and control can be realized timed or instant advertising, news, weather, property notifications and other information, the first time the freshest information passed to the audience groups; Focus of this mode of transmission can be broken down audience, distinguished audience demand, optimizing communication process and improve the accuracy of audience coverage, dissemination of results to achieve the optimal, in the building TV, banking, community , railway stations, airports and other advertising and information distribution market has broad application prospects.

2 hardware system architecture

Use the main processor of the system S igma Designs companys professional-grade high-definition video decoder chip EM8623L. The chip also integrates a V ideo Decoder (R ISC), ARM, DSP three chips, support includes MPEG - 1 / 2 / 4 SD / HD, WMV9 SD / HD, D ivx, H 264, VC - 1, etc., decode a variety of video formats, audio: MPEG - 1, Layer1 / 2 / 3 (MP3), AC - 3, AAC, PCM, WMA9 and so on. The ARM embedded 200MH z is responsible for controlling the core, 32-bit memory bandwidth, and maximum support for 256MB of DDR, support 64MB of flash memory expansion. Responsible for 32-bit DSP audio processing, 16-bit R ISC processor is responsible for video decoding. EM8623L also has 2D graphics engine and IDE, DV I, PC I, U SB and other rich interface support. The embedded architecture and hardware-based decoder chip solution in terms of cost, power and efficiency can well meet the demand for high-definition media player terminals.

HD media information described in this article published structure of the terminal hardware systems include: high-definition decoder chip EM 8623L; 128MB SDRAM and 8MB flash memory; network interface controller; front panel control circuit; built-in 25-inch notebook SATA hard disk interface; provide high-definition digital multimedia interface (HDM I), high-definition video color component interface (YPbPr), composite video signal interface (V IDEO) and other video interfaces, optical digital audio interface (S / PD IF), coaxial digital audio interface ( COAX IAL), two-channel stereo audio interface (R-AUD IO - L) and other audio interfaces. Also provides a USB2 0 interface with an external removable storage device, which plays audio and video resources, and provide the firmware update function.

3 Software Design

3.1 software architecture design

Software system based on principles of embedded systems and multimedia information publishing applications for design, system architecture in Figure 1, mainly driven by the hardware layer, real-time operating system layer, middle layer and application layer. Hardware drivers layer is most closely associated with the hardware, software layers, including audio and video output interfaces, N IC, SATA controller, USB2 0 controller, F lash, RS232 and front panel / remote control drivers, and hardware address, and access register the API, is the system stable and efficient operation of the important foundation. Loading device drivers can start with the operating system loaded in the kernel can also be followed up in the operating system, a separate module is loaded, concrete driver in the kernel compile time configuration is loaded, making the kernel size setting more flexible, convenient space under the F lash make appropriate adjustments.

Figure 1, the system software structure

Real-time operating system is a core part of embedded device software. uC linux is designed for embedded processor features a real-time operating system, it inherits the standard L inux powerful network functions and multi-task management, supports multiple file systems, provides a standard rich API, with the implementation of high efficiency, small footprint, scalability, strong and good portability and other advantages. In addition, he also designed for non-MMU processor design, and the L inux memory management and process management has been rewritten to meet the development requirements of the processor without MMU. As EM8623L is a processor without MMU, so the system uses uC linux as the operating system kernel.

Middle tier includes proprietary protocol stack modules, PPPOE (Po int-to-po intpro tocol over E thernet) modules, audio and video decoding module and the 2D graphics accelerator module. These modules in real-time operating system layer and application layer, up to provide API interfaces for applications to call down real-time operating system implementation through the API level interface functions to the hardware driver mapping. Private stack module is a proprietary UDP-based reliable datagram protocol, a large amount of data to support remote downloading and autonomous design. The stack can take a different packet loss rate of adaptive re-issued, replacement and other fault tolerance mechanisms to overcome the UDP protocol for data transmission is not reliable. Higher packet loss rate in the network the network environment can show a more robust data reception, the better to meet the large volume of data, high-speed and reliable HD media downloads, effective bandwidth, data download rates of up to 80% of the existing . PPPOE ADSL network access module features support system through a standard open source PPPOE on L inux code into the embedded uC linux kernel implementation. Audio and video decoding module developed by Sigma Designs is a complete file player, for playing EM86231 supports multi-standard pronunciation hardware decoding video files and advanced display processing capabilities (support HDM I / YPbPr / AV and other video output and S / PDIF , two-channel audio output, etc.). 2D graphics accelerator to support high-speed OSD and GU I, to provide high-quality high-definition display images.

Software application layer is the top level, to achieve the main function of the system applications, including remote control receiving and processing, graphical user interface display, HD media, download files locally, online upgrade, system log of the remote server up certification , video / audio / pictures / words such as sharing flight control playback and mix shows.

3.2 System design of the task

Released for HD media information required accuracy, and timeliness of real-time and the system design of the four systems the main tasks are: master the task, time threads, thread and flying missions word play thread. The master is responsible for scheduling tasks, monitoring server on the main window and the flight control command issued by the word window (such as pause, fast forward, rewind, stop, continue other operations), and downloaded to the local hard drive under a variety of programming Play the corresponding single-media programs can play in order, insertion control and manual control by the time broadcast shows. Network tasks, including control of the thread thread and data messaging download thread. Control information and data send and receive threads to complete high-definition media file thread remote download and local storage, the main thread is responsible for sending and receiving control information Xieyi handshake, that protocol information is not initiated until the end of the 200ms agreed protocol information within the reach, it times out and determine Xin Xi re-issued; data network thread is responsible for pushing the media files downloaded and stored locally.

Time thread is responsible for access to the current system time, then the control system time and local time, each record in the list of play time, insertion control list of the playing time of each record to compare, if you have time to play records , the corresponding player deal, the player deal with the main window and sub-fly word window. Fly word word play thread implementation cycle under the fly playlists, fly the word list spots, flying time control word order in the list of programs broadcast the appropriate word to fly operation. Specific steps the whole system work flow is as follows:

(1) start the bootloader, the necessary hardware initialization;

(2) start from the flash rom fs;

(3) to determine whether to start a successful, if successful, then extract the app bin gz, the kernel initialization, load the appropriate device driver, start the top of the application.

(4) If unsuccessful read from the hard disk rom fs b in, and write ROM, and repeated (3) operation;

(5) read the default configuration parameters in flash and set the corresponding parameters;

(6) start the DHCP, to obtain IP address, gateway, DNS server, IP, subnet mask, etc.;

(7) start network thread task of docking the terminal and the server, registration certification; media data downloads; if a successful connection with the server, then sync terminal system time;

(8) Start the master task, in accordance with the play list of priorities Play the broadcast program. Master the task flow chart shown in Figure 2.

Figure 2 master task flow

4 Conclusion

Paper designed a media release on HD EM8623L terminals with low power consumption, compact structure, high stability and so on. Efficient and reliable high-definition media support for local programs to download; support the order of playback, instant playback and playback time; supports almost all smooth playback of HD video media; to video, audio, pictures, and scrolling marquee players such as the combination of multimedia information; and accept real-time monitoring front-end control system; with a variety of audio and video output interfaces, support 1080P HD display pure. Combination of front-end current control system in banks, airports and other places have been widely promoted and applied.

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