摄像头预览【v4l2+framebuffer】

#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=10;
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

    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;
    int xpos = (vinfo.xres-width)/2;
    int ypos = (vinfo.yres-height)/2;

    for ( y = ypos; y < height + ypos; ++y) {
        for (j = 0, x=xpos; 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);
    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;

        }

        //if(frames%10 == 0)
        {
            printf("\r %4d ", frames);
            fputc ('.', stdout);
            fflush (stdout);
        }

    }
    printf("\n");
}

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, &cap)) {
        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_NONE;

    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/video1";

    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;
}