转自：http://blog.csdn.net/kickxxx/article/details/6336346
在网上找了一个测试程序， 看了看，是根据capture.c修改的。测试步骤如下 1. gcc -o capture_image capture_image.c 2. ctrl+alt+f1 切换到ubuntu的控制台，切换到控制台模式是因为在图形模式下看不到测试图形，这可能和framebuffer的设置有关 3. sudo modprobe vivi 4. sudo ./capture_image -d /dev/video0 这时可以看到在屏幕左上角有一个640x480大小窗口，内容是彩色条格，彩色条格不停的移动，持续时间5秒 在ubuntu下还可以使用cheese测试 1. sudo apt-get install cheese 2. sudo modprobe vivi 2. 启动 cheese后，就可以看到滚动的彩色条格 附上测试程序 [c-sharp] view plain copy #include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <getopt.h> #include <fcntl.h> #include <unistd.h> #include <errno.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/time.h> #include <sys/mman.h> #include <sys/ioctl.h> #include <asm/types.h> #include <Linux/videodev2.h> #include <linux/fb.h> #define CLEAR(x) memset (&(x), 0, sizeof (x)) struct buffer { void * start; size_t length; }; static char * dev_name = NULL; static int fd = -1; struct buffer * buffers = NULL; static unsigned int n_buffers = 0; static int time_in_sec_capture=5; static int fbfd = -1; static struct fb_var_screeninfo vinfo; static struct fb_fix_screeninfo finfo; static char *fbp=NULL; static long screensize=0; static void errno_exit (const char * s) { fprintf (stderr, "%s error %d, %s/n",s, errno, strerror (errno)); exit (EXIT_FAILURE); } static int xioctl (int fd,int request,void * arg) { int r; do r = ioctl (fd, request, arg); while (-1 == r && EINTR == errno); return r; } inline int clip(int value, int min, int max) { return (value > max ? max : value < min ? min : value); } static void process_image (const void * p){ //ConvertYUVToRGB32 1; unsigned char* in=(char*)p; int width=640; int height=480; int istride=1280; int x,y,j; int y0,u,y1,v,r,g,b; long location=0; for ( y = 100; y < height + 100; ++y) { for (j = 0, x=100; j < width * 2 ; j += 4,x +=2) { location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) + (y+vinfo.yoffset) * finfo.line_length; y0 = in[j]; u = in[j + 1] - 128; y1 = in[j + 2]; v = in[j + 3] - 128; r = (298 * y0 + 409 * v + 128) >> 8; g = (298 * y0 - 100 * u - 208 * v + 128) >> 8; b = (298 * y0 + 516 * u + 128) >> 8; fbp[ location + 0] = clip(b, 0, 255); fbp[ location + 1] = clip(g, 0, 255); fbp[ location + 2] = clip(r, 0, 255); fbp[ location + 3] = 255; r = (298 * y1 + 409 * v + 128) >> 8; g = (298 * y1 - 100 * u - 208 * v + 128) >> 8; b = (298 * y1 + 516 * u + 128) >> 8; fbp[ location + 4] = clip(b, 0, 255); fbp[ location + 5] = clip(g, 0, 255); fbp[ location + 6] = clip(r, 0, 255); fbp[ location + 7] = 255; } in +=istride; } } static int read_frame (void) { struct v4l2_buffer buf; unsigned int i; CLEAR (buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; if (-1 == xioctl (fd, VIDIOC_DQBUF, &buf)) { switch (errno) { case EAGAIN: return 0; case EIO: default: errno_exit ("VIDIOC_DQBUF"); } } assert (buf.index < n_buffers); printf("v4l2_pix_format->field(%d)/n", buf.field); //assert (buf.field ==V4L2_FIELD_NONE); process_image (buffers[buf.index].start); if (-1 == xioctl (fd, VIDIOC_QBUF, &buf)) errno_exit ("VIDIOC_QBUF"); return 1; } static void run (void) { unsigned int count; int frames; frames = 30 * time_in_sec_capture; while (frames-- > 0) { for (;;) { fd_set fds; struct timeval tv; int r; FD_ZERO (&fds); FD_SET (fd, &fds); tv.tv_sec = 2; tv.tv_usec = 0; r = select (fd + 1, &fds, NULL, NULL, &tv); if (-1 == r) { if (EINTR == errno) continue; errno_exit ("select"); } if (0 == r) { fprintf (stderr, "select timeout/n"); exit (EXIT_FAILURE); } if (read_frame ()) break; } } } static void stop_capturing (void) { enum v4l2_buf_type type; type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (-1 == xioctl (fd, VIDIOC_STREAMOFF, &type)) errno_exit ("VIDIOC_STREAMOFF"); } static void start_capturing (void) { unsigned int i; enum v4l2_buf_type type; for (i = 0; i < n_buffers; ++i) { struct v4l2_buffer buf; CLEAR (buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = i; if (-1 == xioctl (fd, VIDIOC_QBUF, &buf)) errno_exit ("VIDIOC_QBUF"); } type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (-1 == xioctl (fd, VIDIOC_STREAMON, &type)) errno_exit ("VIDIOC_STREAMON"); } static void uninit_device (void) { unsigned int i; for (i = 0; i < n_buffers; ++i) if (-1 == munmap (buffers[i].start, buffers[i].length)) errno_exit ("munmap"); if (-1 == munmap(fbp, screensize)) { printf(" Error: framebuffer device munmap() failed./n"); exit (EXIT_FAILURE) ; } free (buffers); } static void init_mmap (void) { struct v4l2_requestbuffers req; //mmap framebuffer fbp = (char *)mmap(NULL,screensize,PROT_READ | PROT_WRITE,MAP_SHARED ,fbfd, 0); if ((int)fbp == -1) { printf("Error: failed to map framebuffer device to memory./n"); exit (EXIT_FAILURE) ; } memset(fbp, 0, screensize); CLEAR (req); req.count = 4; req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; req.memory = V4L2_MEMORY_MMAP; if (-1 == xioctl (fd, VIDIOC_REQBUFS, &req)) { if (EINVAL == errno) { fprintf (stderr, "%s does not support memory mapping/n", dev_name); exit (EXIT_FAILURE); } else { errno_exit ("VIDIOC_REQBUFS"); } } if (req.count < 4) { //if (req.count < 2) fprintf (stderr, "Insufficient buffer memory on %s/n",dev_name); exit (EXIT_FAILURE); } buffers = calloc (req.count, sizeof (*buffers)); if (!buffers) { fprintf (stderr, "Out of memory/n"); exit (EXIT_FAILURE); } for (n_buffers = 0; n_buffers < req.count; ++n_buffers) { struct v4l2_buffer buf; CLEAR (buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = n_buffers; if (-1 == xioctl (fd, VIDIOC_QUERYBUF, &buf)) errno_exit ("VIDIOC_QUERYBUF"); buffers[n_buffers].length = buf.length; buffers[n_buffers].start =mmap (NULL,buf.length,PROT_READ | PROT_WRITE ,MAP_SHARED,fd, buf.m.offset); if (MAP_FAILED == buffers[n_buffers].start) errno_exit ("mmap"); } } static void init_device (void) { struct v4l2_capability cap; struct v4l2_cropcap cropcap; struct v4l2_crop crop; struct v4l2_format fmt; unsigned int min; // Get fixed screen information if (-1==xioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) { printf("Error reading fixed information./n"); exit (EXIT_FAILURE); } // Get variable screen information if (-1==xioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) { printf("Error reading variable information./n"); exit (EXIT_FAILURE); } screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8; if (-1 == xioctl (fd, VIDIOC_QUERYCAP, ∩)) { if (EINVAL == errno) { fprintf (stderr, "%s is no V4L2 device/n",dev_name); exit (EXIT_FAILURE); } else { errno_exit ("VIDIOC_QUERYCAP"); } } if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) { fprintf (stderr, "%s is no video capture device/n",dev_name); exit (EXIT_FAILURE); } if (!(cap.capabilities & V4L2_CAP_STREAMING)) { fprintf (stderr, "%s does not support streaming i/o/n",dev_name); exit (EXIT_FAILURE); } CLEAR (cropcap); cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (0 == xioctl (fd, VIDIOC_CROPCAP, &cropcap)) { crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; crop.c = cropcap.defrect; if (-1 == xioctl (fd, VIDIOC_S_CROP, &crop)) { switch (errno) { case EINVAL: break; default: break; } } }else { } CLEAR (fmt); fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; fmt.fmt.pix.width = 640; fmt.fmt.pix.height = 480; fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; if (-1 == xioctl (fd, VIDIOC_S_FMT, &fmt)) errno_exit ("VIDIOC_S_FMT"); init_mmap (); } static void close_device (void) { if (-1 == close (fd)) errno_exit ("close"); fd = -1; close(fbfd); } static void open_device (void) { struct stat st; if (-1 == stat (dev_name, &st)) { fprintf (stderr, "Cannot identify '%s': %d, %s/n",dev_name, errno, strerror (errno)); exit (EXIT_FAILURE); } if (!S_ISCHR (st.st_mode)) { fprintf (stderr, "%s is no device/n", dev_name); exit (EXIT_FAILURE); } //open framebuffer fbfd = open("/dev/fb0", O_RDWR); if (fbfd==-1) { printf("Error: cannot open framebuffer device./n"); exit (EXIT_FAILURE); } //open camera fd = open (dev_name, O_RDWR| O_NONBLOCK, 0); if (-1 == fd) { fprintf (stderr, "Cannot open '%s': %d, %s/n",dev_name, errno, strerror (errno)); exit (EXIT_FAILURE); } } static void usage (FILE * fp,int argc,char ** argv) { fprintf (fp, "Usage: %s [options]/n/n" "Options:/n" "-d | --device name Video device name [/dev/video]/n" "-h | --help Print this message/n" "-t | --how long will display in seconds/n" "", argv[0]); } static const char short_options [] = "d:ht:"; static const struct option long_options [] = { { "device", required_argument, NULL, 'd' }, { "help", no_argument, NULL, 'h' }, { "time", no_argument, NULL, 't' }, { 0, 0, 0, 0 } }; int main (int argc,char ** argv) { dev_name = "/dev/video0"; for (;;) { int index; int c; c = getopt_long (argc, argv,short_options, long_options,&index); if (-1 == c) break; switch (c) { case 0: break; case 'd': dev_name = optarg; break; case 'h': usage (stdout, argc, argv); exit (EXIT_SUCCESS); case 't': time_in_sec_capture = atoi(optarg); break; default: usage (stderr, argc, argv); exit (EXIT_FAILURE); } } open_device (); init_device (); start_capturing (); run (); stop_capturing (); uninit_device (); close_device (); exit (EXIT_SUCCESS); return 0; } 这个测试程序是根据vivi驱动hard code的， 并不一定适合其他的camera驱动 比如，我手头上的logitech stv06xx usb camera, 因为不支持640x480模式，参见代码59 60行， 代码348行 if (-1 == xioctl (fd, VIDIOC_S_FMT, &fmt)) 应该是个协商的过程， 343 fmt.fmt.pix.width = 640; 344 fmt.fmt.pix.height = 480; 345 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; 346 fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; 这几行只是应用的期望格式，驱动会根据这个格式选择一个相近的格式返回，应用最后的显示处理要根据返回的格式进行处理，即process_image要做相应修改
本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/sky-heaven/p/6904014.html，如需转载请自行联系原作者
