Video Capture System Based on PXA270 Platform

In this paper, the author introduces a video capture system based on embedded Linux PXA270 platform. First, the paper briefly introduces PXA270 platform. The author then describes implementation of video capture on the platform. The system captures a real-time video stream by USB camera and designs video program by Video 4 Linux APIs. The paper particularly presents the method and process of realizing video data capture, as well as how to implement the application to target board. DOI: 10.4018/japuc.2012010104 30 International Journal of Advanced Pervasive and Ubiquitous Computing, 4(1), 29-34, January-March 2012 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. 2. PXA270 PLATFORM INTRODUCTION The PXA270 processor is the first Intel XScale technology-based processor to include Intel Wireless MMX technology. This enables highperformance multimedia acceleration with an industry proven instruction set. Enabled by Intel Quick Capture technology, the PXA270 provides one of the industry’s most flexible and powerful camera interfaces for capturing digital images and video (Lin, Liu, Xiong, Wang, & Zhang, 2007). A set of serial devices and general-system resources offers computational and connectivity capability for a variety of applications. Figure 1 shows the development platform of PXA270 processor. The paper introduces a video data capture system based on PXA270 platform. 3. VIDEO CAPTURE SYSTEM In Linux, device driver to the application details of shielding concrete implementation of hardware, so the application can operate like a normal file to operate as an external device. In Linux, the normal use of video capture device relies on the support of Video4Linux standards (Liao, Zhang, Peng, & Li, 2010). Video4Linux (referred to as the V4L) is a Linux kernel on the video device driver that is for video equipment to provide a series of application programming interface functions, these video devices including TV cards, video capture card and USB cameras. The general process of video capture is: (1) Open the video device; (2) Read the device information; (3) Video capture; (4) On the acquisition of video data processing and display; (5) Off the video equipment. Video capture comes from two methods: (1) Read directly from the device; (2) Memory map. The system uses the second method for video acquisition, and the advantage is when using memory mapping, the direct use of mmap () system call allows processes by mapping a regular file with the shared memory. Common file address space is mapped to the process, the process can access the common memory, the same as the file access, do not have to call read (), write () and other operations. The use of shared memory communication is an obvious advantage is efficiency, because the process can read and write memory directly without any data copies. Using memory-mapped portion of video capture source code is as follows: (1) call VIDIOCGBUF information for mapping the buffer ioctl (vd-> fd, VIDIOCGBUF, & (vd -> mbuf)) (2) to mmap with video_mbuf bound int v4l_mmap_init (v4l_Device * vd) {if (v4l_get_mbuf (vd) ; map = mmap (0, vd-> mbuf.size, Port_READ | PORT_WRITE, MAP_SHARED, vd-> fd)) (3) pre-set for image capture int v4l_grab_init (v4l_device * vd) {vd-> mmap.width = 640; / / set the image window vd-> mmap. height = 480; / / window size is 640 × 480 vd-> mmap.format = VEDIO_PALETTE_YUV420P; / / sample format for YUV420P ; ...} (4) start a call interception VIDIOCMCAPTURE ioctl (vd-> fd, VIDIOCMCAPTURE, & (vd-> mmap)); (5) call to wait for an interception VIDIOSYNC end If (ioctl (vd-> fd, VIDIOSYNC, & frame) the function returns successfully, said an acquisition has been completed, the collected 4 more pages are available in the full version of this document, which may be purchased using the "Add to Cart" button on the product's webpage: www.igi-global.com/article/video-capture-system-basedpxa270/68804?camid=4v1 This title is available in InfoSci-Journals, InfoSci-Journal Disciplines Communications and Social Science. Recommend this product to your librarian: www.igi-global.com/e-resources/libraryrecommendation/?id=2