V4L2 camera 驱动 capture测试程序【转】

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

. gcc -o capture_image capture_image.c

. 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

. sudo modprobe vivi

. 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

.  sudo apt-get install cheese

. sudo modprobe vivi

. 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 = -;
    struct buffer * buffers = NULL;
    static unsigned int n_buffers = ;
    static int time_in_sec_capture=;
    static int fbfd = -;
    static struct fb_var_screeninfo vinfo;
    static struct fb_fix_screeninfo finfo;
    static char *fbp=NULL;
    static long screensize=;  

    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 (- == 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
        ;
        unsigned char* in=(char*)p;
        int width=;
        int height=;
        int istride=;
        int x,y,j;
        int y0,u,y1,v,r,g,b;
        long location=;  

        for ( y = ; y < height + ; ++y) {
            for (j = , x=; j < width *  ; j += ,x +=) {
              location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/) +
                (y+vinfo.yoffset) * finfo.line_length;  

              y0 = in[j];
              u = in[j + ] - ;
              y1 = in[j + ];
              v = in[j + ] - ;          

              r = ( * y0 +  * v + ) >> ;
              g = ( * y0 -  * u -  * v + ) >> ;
              b = ( * y0 +  * u + ) >> ;  

              fbp[ location + ] = clip(b, , );
              fbp[ location + ] = clip(g, , );
              fbp[ location + ] = clip(r, , );
              fbp[ location + ] = ;      

              r = ( * y1 +  * v + ) >> ;
              g = ( * y1 -  * u -  * v + ) >> ;
              b = ( * y1 +  * u + ) >> ;  

               fbp[ location + ] = clip(b, , );
              fbp[ location + ] = clip(g, , );
              fbp[ location + ] = clip(r, , );
              fbp[ location + ] = ;
              }
            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 (- == xioctl (fd, VIDIOC_DQBUF, &buf)) {
            switch (errno) {
            case EAGAIN:
            return ;
            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 (- == xioctl (fd, VIDIOC_QBUF, &buf))
            errno_exit ("VIDIOC_QBUF");  

        return ;
    }  

    static void run (void)
    {
        unsigned int count;
        int frames;
        frames =  * time_in_sec_capture;  

        while (frames-- > ) {
            for (;;) {
                fd_set fds;
                struct timeval tv;
                int r;
                FD_ZERO (&fds);
                FD_SET (fd, &fds);  

                tv.tv_sec = ;
                tv.tv_usec = ;  

                r = select (fd + , &fds, NULL, NULL, &tv);  

                if (- == r) {
                    if (EINTR == errno)
                        continue;
                    errno_exit ("select");
                }  

                if ( == 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 (- == xioctl (fd, VIDIOC_STREAMOFF, &type))
            errno_exit ("VIDIOC_STREAMOFF");
    }  

    static void start_capturing (void)
    {
        unsigned int i;
        enum v4l2_buf_type type;  

        for (i = ; 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 (- == xioctl (fd, VIDIOC_QBUF, &buf))
                errno_exit ("VIDIOC_QBUF");
            }  

        type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  

        if (- == xioctl (fd, VIDIOC_STREAMON, &type))
            errno_exit ("VIDIOC_STREAMON");  

    }  

    static void uninit_device (void)
    {
        unsigned int i;  

        for (i = ; i < n_buffers; ++i)
            if (- == munmap (buffers[i].start, buffers[i].length))
                errno_exit ("munmap");  

        if (- == 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, );
            if ((int)fbp == -) {
                printf("Error: failed to map framebuffer device to memory./n");
                exit (EXIT_FAILURE) ;
            }
        memset(fbp, , screensize);
        CLEAR (req);  

        req.count = ;
        req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        req.memory = V4L2_MEMORY_MMAP;  

        if (- == 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 < ) {    //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 = ; 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 (- == 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 (-==xioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
                printf("Error reading fixed information./n");
                exit (EXIT_FAILURE);
            }  

            // Get variable screen information
         if (-==xioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
                printf("Error reading variable information./n");
                exit (EXIT_FAILURE);
           }
        screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / ;  

        if (- == 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 ( == xioctl (fd, VIDIOC_CROPCAP, &cropcap)) {
            crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            crop.c = cropcap.defrect;  

            if (- == 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 = ;
        fmt.fmt.pix.height = ;
        fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
        fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;  

        if (- == xioctl (fd, VIDIOC_S_FMT, &fmt))
            errno_exit ("VIDIOC_S_FMT");  

        init_mmap ();  

    }  

    static void close_device (void)
    {
        if (- == close (fd))
        errno_exit ("close");
        fd = -;
        close(fbfd);
    }  

    static void open_device (void)
    {
        struct stat st;    

        if (- == 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==-) {
                printf("Error: cannot open framebuffer device./n");
                exit (EXIT_FAILURE);
            }  

        //open camera
        fd = open (dev_name, O_RDWR| O_NONBLOCK, );  

        if (- == 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[]);
    }  

    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' },
    { , , ,  }
    };  

    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 (- == c)
            break;  

            switch (c) {
            case :
            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 ;
    }  

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 (- == xioctl (fd, VIDIOC_S_FMT, &fmt)) 应该是个协商的过程，
   fmt.fmt.pix.width = ;
   fmt.fmt.pix.height = ;
   fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
   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