The Design Of Video Transmission System Based On USB 2.0 And Streaming Technologies

1. The purpose of the topic researchIn multimedia information, the video frequency information shares the mostin the information. Compared with the analogy video, the digital video has theobvious advantage at memory, editing, transmission etc. but the information ofthe digital video takes much space. To take the 320×240 resolution for VGA asan example, suppose to the broadcast speed as 60 frames per sec., and record theRGB information of those pixels with 24 bits of binary system, its data measuresabout 105.469 Mbits. It is obvious that, the data of the video which didn'tcompressed would be over the 100 Mbits for one second. And it requests thetransmission for the higher speed, lower the mistake rate. The characteristics likevast data, real time of the video information show that the equipments are putforward the higher request towards catch, transmission, memory and display.The technique of streaming is a kind of multimedia applied technique thatdevelops from the Internet, its main characteristics is transmitting the multimediafiles with flowing. Streaming media solves the low bandwidth network totransmit the multimedia information. For streaming not only can carry out realtime broadcasting the sound, video and the multimedia contents, but alsoordering programme. When receiving, processing and rendering a streamingmedia file at the client, that file will not take up a great deal of saving space, anddelete after transacted and finished playing. Streaming media applied to transmit,processing video data, which is lower the requests of the bus speed and thesaving space of the client.The DirectShow is the multimedia structure developed by the MicrosoftCompany. It defines a series of modules (Filters), for controlling and handlingthe flowing multimedia data took time stamp, released with DirectX SDK. TheDirectShow provides the powerful support for catching and rendering of theflowing multimedia. Make use of the DirectShow can very expediently catchfrom the collecting card which supporting WDM (Windows Driver Model), andhandle various medium, making rendering multimedia data become easy toaccomplish. At the same time, the DirectShow is an open developmentenvironment, can customize the module according to the demand. It providesdoable project for developing multi-video sources collection, and multi-videoformat processing, which is use of streaming media.Current real time video transmits with the bus, such as: the PCI, 1394 andUSB (the Universal Serial Bus). The relative characteristic of the three, theprotocol of the USB high speed is fast, universal, credible, saving power, hotplug etc. Compare with traditional video transmission system which based onPCI bus or 1394 bus, it is flexible, universal, convenient install, easily expand,especially in the occasion needing the notebook and other portable equipmentsfor video output. The USB2.0 breaks the bottleneck of the USB1.1, can providethe high speed for collecting and transmitting vast data, and can satisfy theresolution as the need that common QVGA video collecting and transmitting. Itdoes not need compress the data, thus that it raises up real time, lower the cost ofthe system.Presently, among the flat panel displays, the Organic Light EmittingDevice (OLED) has the advantages, such as the self-moving light, the breadthangle of view, the quickly responding speed, the weight is light,and can bemanufactured in the gentle bottom of underlay. In recent years it is favored byscience and the industry, and develops quickly. The topic group namely carriedout the design and simulation work of the AMOLED screen's drive circuit. Thework is about the physical design of the AMOLED intergrated screen ciruit,simulation and researching the assorted periphery ASIC. Now we already haveformed the innovation and feasible scheme. With the foundation above, thisarticle introduces the research and development of AMOLED's video displayingand transferring system based on streaming and USB2.0 technology in detail.In this information technology changing quickly period, people haveincreasingly exigent and increasingly high requirement for collecting andtransforming the video image. The research and development of AMOLEDdisplay drive circuit based on streaming and USB2.0 technology aims at thosefeatures, such as large data of video image, many data format and high realtime.Adopting the streaming technology catching and disposing the video data canreduce the requirements for the speed of the transmit bus and the memory spaceof client, and realize multiple video sources. Using with USB2.0 technology canrealize transforming high speedly, stably, and processing data, also enhancemobility of system and reduce cost. So that, it is satifed the development of thetopic group and the future of video application that reaserching and developingthe AMOLED's video displaying and transferring system based on streamingand USB2.0 technology.2. System designObtaining the video source is an important part of the system design.Nowadays is is a science and technology developing quickly'society that videoexist with multi-way. It becomes an emphasis of obtaining mode of the videosource that how to obtain needed information and make video source richness.The system adopts the streaming for video source obtaining and videoprocessing.Video dataVideo Data BufferUSB DataCommunicationSRAMCPLDOLEDLineDriveOLED Row DriveOLEDScreenUSB DeviceDirectShowUSB BusApplicationVideo DataProcessingApplicationVideo Frame GrabUSB ChipFigure 1 Video Transmition SystemFigure 1 show that what composes of the video transmitting system. Thewhole system is divided into three parts: the Application procedure on the host,the USB periphery and the drive circuit of OLED. There are many ways toobtain the data of multimedia, such as: internet, pickup camera, collection cardand video files, etc. In order to satisfy the requirement of OLED display screen,we take 320×240 resolution video file with MPEG compression for example.The application controls the component of DirectShow to decode the video dataobtained from the video files. Then video data decoded will be saved intodatabuffer with 24-bits RGB format. The video frame grab component replicatesone frame data from data buffer, and sends the video data to buffer module. Thevideo data buffer module performs blocking and parcel with video data, for theneed of streaming data's transmission. At the same time, the video card showsthe video data read from data buffer on the screen. If we transfer 320 * 240resolution image contained data about 255kbytes for a second, the data will bemade up to 13.5Mbytes. Since the USB2.0 has the feature of the swiftnesstransfer speed, could be realized the large data transfer. The application controlsthe USB data communication module to get the video data packages from thevideo data buffer module, and continuesly send the data to USB device throughthe USB bus with synchronous transmission mode.The USB2.0 chip sends the video data package to CPLD with GPIFinterface. Then CPLD upacks reform and save the video data to SRAMgroup.The SRAM group is formed of twain pieces same SRAM. The CPLDaccesses the twain pieces of SRAM in turn, which ensures the real time of videodata processing. When the OLED needs viewdata, the CPLD can get video datafrom the SRAM group directly, and then control the drive circuit to display theimages.3. ConclusionThis article is based on USB2.0 and streaming technology. It supplys theAMOLED's display with a video source and a transmission avenue. The majorreaserch works are the following:First, analyses the principle of streaming system, and design the videoobtaining processing module with streaming component (DirectShow) byprogramming. Make use of USB development's Base Class supplied by CypressCorporation and Windows multithreading programme method to design USBCommunication Module.Second, analyses realize theory ofsynchronous transmission on USB busand the hierarchical structure of the WDM driver. According to the requirementof video transmission, programme USB driver.Third, make use of configuring endpoints and GPIF interface technology ofthe Cypress corporate's FX2 series chip, design the USB firmware which can fitthe requirement of transforming video data by high speed.Forth, design the USB periphery application circuit and the circuit for videotransmission and store. Design with the Verilog HDL language and realize theGPIF interface between USB and CPLD, and the control module of the datatransmission memory circuit integrated on one chip.In this article we go into streaming and USB2.0 technology. Also we design the videotransmission system of the 320×240 resolution of the AMOLED screen. And we develop thevideo obtain module and processing module based on streaming technology, USBdriver ,USB firmware and USB peripheral ciciut. We through analysesing and debugging theUSB driver, USB firmware and flowing data transmission controlled by CPLD, make thedesign come to an expectant design objective. And we get the desire control signasl andvideo data flows which can satisfy with displaying requirement by the 320×240 resolution ofthe AMOLED screen.