v4l2_openvc

main.cpp

#include <opencv2/opencv.hpp>
#include <iostream>
#include <stdio.h>
#include "v4ldevice.h"

using namespace cv;

void ShowImage(char* Name, IplImage* Img, int Attribute )
{
    cvNamedWindow(Name, Attribute );
    cvShowImage( Name, Img );
    cvWaitKey(0);
    cvDestroyWindow( Name );
}



int main ()
{

    IplImage* pOpenCVImage;
    IplImage* pColorCVImage;

    CvSize ImageSize;
    unsigned char* ImageBuffer = NULL;
    int wKey = -1;

    ImageSize.width = 640;
    ImageSize.height = 480;

    cvNamedWindow( (char*)"Camera", 1 );


    printf("Program started\n");


    pOpenCVImage = cvCreateImage(ImageSize , IPL_DEPTH_8U, 1 ); // Grayscale
    pColorCVImage = cvCreateImage(ImageSize , IPL_DEPTH_8U, 3 ); // Color image



    open_device((char*)"/dev/video0");
    init_device(ImageSize.width, ImageSize.height);


    printf("Start capturing\n");



    start_capturing();



    while(wKey == -1 )
    {
        ImageBuffer = snapFrame();

        if( ImageBuffer != NULL )
        {
            memcpy( pOpenCVImage->imageData, ImageBuffer, pOpenCVImage->imageSize);
            cvCvtColor(pOpenCVImage,pColorCVImage,CV_BayerGB2RGB); // Create a color image from the raw data

            cvShowImage( (char*)"Camera",pColorCVImage);
            wKey = cvWaitKey(10);
        }
        else
        {
            printf("No image buffer retrieved.\n");
            break;
        }
    }

    cvDestroyWindow( (char*)"Camera" );
    stop_capturing();
    uninit_device();
    close_device();

    printf("Program ended\n");

    return 0;

}

Makefile

all: opencv-test


opencv-test: main.cpp v4ldevice.cpp
	$(CXX) -Wall -g -O0 -o opencv-test main.cpp v4ldevice.cpp $(shell pkg-config --libs-only-l opencv libv4l2)

clean:
	$(RM) *.o
	$(RM) opencv-test

v4ldevice.cpp

/*
 *  V4L2 video capture example
 *
 *  This program can be used and distributed without restrictions.
 *
 *      This program is provided with the V4L2 API
 * see http://linuxtv.org/docs.php for more information
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>


#include <fcntl.h>              /* low-level i/o */
#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 <linux/videodev2.h>

#define CLEAR(x) memset(&(x), 0, sizeof(x))

enum io_method
{
    IO_METHOD_READ,
    IO_METHOD_MMAP,
    IO_METHOD_USERPTR,
};

struct buffer
{
    void   *start;
    size_t  length;
};

struct v4l2_buffer buf;

char            dev_name[1024];
enum io_method   io = IO_METHOD_MMAP;
int              fd = -1;
struct buffer          *buffers;
unsigned int     n_buffers;
int              out_buf;
int              force_format = 1;
int              frame_count = 10;


void errno_exit (const char *s)
{
    fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
    exit(EXIT_FAILURE);
}


int xioctl (int fh, int request, void *arg)
{
    int r;

    do
    {
        r = ioctl(fh, request, arg);
    } while (-1 == r && EINTR == errno);

    return r;
}


int read_frame (void)
{
    //struct v4l2_buffer buf;
    unsigned int i;

    switch (io)
    {
        case IO_METHOD_READ:
        {
            if (-1 == read(fd, buffers[0].start, buffers[0].length))
            {
                switch (errno)
                {
                    case EAGAIN:
                        return 0;

                    case EIO:
                        /* Could ignore EIO, see spec. */

                        /* fall through */

                    default:
                        errno_exit("read");
                }
            }

            break;
        }
        case IO_METHOD_MMAP:
        {
            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:
                        /* Could ignore EIO, see spec. */

                        /* fall through */

                    default:
                        errno_exit("VIDIOC_DQBUF");
                }
            }

            assert(buf.index < n_buffers);

           

            if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
                errno_exit("VIDIOC_QBUF");
            break;
        }
        case IO_METHOD_USERPTR:
        {
            CLEAR(buf);

            buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = V4L2_MEMORY_USERPTR;

            if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
            {
                switch (errno)
                {
                    case EAGAIN:
                        return 0;

                    case EIO:
                        /* Could ignore EIO, see spec. */

                        /* fall through */

                    default:
                    {
                        errno_exit("VIDIOC_DQBUF");
                    }
                }
            }

            for (i = 0; i < n_buffers; ++i)
            {
                if (buf.m.userptr == (unsigned long)buffers[i].start
                    && buf.length == buffers[i].length)
                    break;
            }
            assert(i < n_buffers);

           

            if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
            {
                errno_exit("VIDIOC_QBUF");
            }
            break;
        }
    }

    return 1;
}


unsigned char* snapFrame()
{
      //printf("Start snapFrame\n");
      for (;;)
      {
	  fd_set fds;
	  struct timeval tv;
	  int r;

	  FD_ZERO(&fds);
	  FD_SET(fd, &fds);

	  /* Timeout. */
	  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;
	  /* EAGAIN - continue select loop. */
      }
      //printf("End snapFrame\n");
      
     // v4l2_buffer* pI = ((v4l2_buffer*)buffers[buf.index].start);
      //return pI;
      return (unsigned char*)buffers[buf.index].start;
 
}

void stop_capturing (void)
{
    enum v4l2_buf_type type;

    switch (io)
    {
        case IO_METHOD_READ:
        {
            /* Nothing to do. */
            break;
        }
        case IO_METHOD_MMAP:
        case IO_METHOD_USERPTR:
            type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
            {
                errno_exit("VIDIOC_STREAMOFF");
            }
            break;
    }
}

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

    switch (io)
    {
        case IO_METHOD_READ:
        {
            /* Nothing to do. */
            break;
        }
        case IO_METHOD_MMAP:
        {
            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");
            }
            break;
        }
        case IO_METHOD_USERPTR:
        {
            for (i = 0; i < n_buffers; ++i)
            {
                struct v4l2_buffer buf;

                CLEAR(buf);
                buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                buf.memory = V4L2_MEMORY_USERPTR;
                buf.index = i;
                buf.m.userptr = (unsigned long)buffers[i].start;
                buf.length = buffers[i].length;

                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");
            }
            break;
        }
    }
}

void uninit_device (void)
{
    unsigned int i;

    switch (io)
    {
        case IO_METHOD_READ:
            free(buffers[0].start);
            break;

        case IO_METHOD_MMAP:
            for (i = 0; i < n_buffers; ++i)
                if (-1 == munmap(buffers[i].start, buffers[i].length))
                    errno_exit("munmap");
            break;

        case IO_METHOD_USERPTR:
            for (i = 0; i < n_buffers; ++i)
                free(buffers[i].start);
            break;
    }

    free(buffers);
}

void init_read (unsigned int buffer_size)
{
    buffers = (buffer*)(calloc(1, sizeof(*buffers)));

    if (!buffers)
    {
        fprintf(stderr, "Out of memory\n");
        exit(EXIT_FAILURE);
    }

    buffers[0].length = buffer_size;
    buffers[0].start = malloc(buffer_size);

    if (!buffers[0].start)
    {
        fprintf(stderr, "Out of memory\n");
        exit(EXIT_FAILURE);
    }
}

void init_mmap (void)
{
    struct v4l2_requestbuffers req;

    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 < 2)                          \
    {
        fprintf(stderr, "Insufficient buffer memory on %s\n",
                dev_name);
        exit(EXIT_FAILURE);
    }

    buffers = (buffer*)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 /* start anywhere */,
                 buf.length,
                 PROT_READ | PROT_WRITE /* required */,
                 MAP_SHARED /* recommended */,
                 fd, buf.m.offset);

        if (MAP_FAILED == buffers[n_buffers].start)
            errno_exit("mmap");
    }
}

void init_userp (unsigned int buffer_size)
{
    struct v4l2_requestbuffers req;

    CLEAR(req);

    req.count  = 4;
    req.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_USERPTR;

    if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req))
    {
        if (EINVAL == errno)
        {
            fprintf(stderr, "%s does not support "
                    "user pointer i/o\n", dev_name);
            exit(EXIT_FAILURE);
        }
        else
        {
            errno_exit("VIDIOC_REQBUFS");
        }
    }

    buffers = (buffer*)calloc(4, sizeof(*buffers));

    if (!buffers)
    {
        fprintf(stderr, "Out of memory\n");
        exit(EXIT_FAILURE);
    }

    for (n_buffers = 0; n_buffers < 4; ++n_buffers)
    {
        buffers[n_buffers].length = buffer_size;
        buffers[n_buffers].start = malloc(buffer_size);

        if (!buffers[n_buffers].start)
        {
            fprintf(stderr, "Out of memory\n");
            exit(EXIT_FAILURE);
        }
    }
}

void init_device ( int width,int height)
{
    struct v4l2_capability cap;
    struct v4l2_cropcap cropcap;
    struct v4l2_crop crop;
    struct v4l2_format fmt;
    unsigned int min;

    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);
    }

    switch (io)
    {
        case IO_METHOD_READ:
        {
            if (!(cap.capabilities & V4L2_CAP_READWRITE))
            {
                fprintf(stderr,
                        "%s does not support read i/o\n",
                        dev_name);
                exit(EXIT_FAILURE);
            }
            break;
        }
        case IO_METHOD_MMAP:
        case IO_METHOD_USERPTR:
        {
            if (!(cap.capabilities & V4L2_CAP_STREAMING))
            {
                fprintf(stderr, "%s does not support streaming i/o\n",
                        dev_name);
                exit(EXIT_FAILURE);
            }
            break;
        }
    }


    /* Select video input, video standard and tune here. */


    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; /* reset to default */

        if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop))
        {
            switch (errno)
            {
                case EINVAL:
                    /* Cropping not supported. */
                    break;
                default:
                    /* Errors ignored. */
                    break;
            }
        }
    }
    else
    {
        /* Errors ignored. */
    }


    CLEAR(fmt);

    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (force_format)
    {
        fmt.fmt.pix.width       = width;
        fmt.fmt.pix.height      = height;
        fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_GREY;
        fmt.fmt.pix.field       = V4L2_FIELD_NONE;

        if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
            errno_exit("VIDIOC_S_FMT");

        /* Note VIDIOC_S_FMT may change width and height. */
    }
    else
    {
        /* Preserve original settings as set by v4l2-ctl for example */
        if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt))
            errno_exit("VIDIOC_G_FMT");
    }

    /* Buggy driver paranoia. */
    min = fmt.fmt.pix.width * 2;
    if (fmt.fmt.pix.bytesperline < min)
        fmt.fmt.pix.bytesperline = min;
    min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
    if (fmt.fmt.pix.sizeimage < min)
        fmt.fmt.pix.sizeimage = min;

    switch (io)
    {
        case IO_METHOD_READ:
            init_read(fmt.fmt.pix.sizeimage);
            break;

        case IO_METHOD_MMAP:
            init_mmap();
            break;

        case IO_METHOD_USERPTR:
            init_userp(fmt.fmt.pix.sizeimage);
            break;
    }
}

void close_device(void)
{
    if (-1 == close(fd))
        errno_exit("close");

    fd = -1;
}

void open_device(char* devicename)
{
    struct stat st;
    strcpy( dev_name,devicename);

    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);
    }

    fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);

    if (-1 == fd) {
        fprintf(stderr, "Cannot open '%s': %d, %s\n",
                dev_name, errno, strerror(errno));
        exit(EXIT_FAILURE);
    }
}

v4ldevice.h

 void open_device(char* devicename); 
 void close_device(void);
 void init_device (int width, int height );
 void init_userp (unsigned int buffer_size);
 void init_mmap (void);
 void init_read (unsigned int buffer_size);
 void uninit_device (void);
 void start_capturing (void);
 void stop_capturing (void);
 int read_frame (void);
 void errno_exit (const char *s);
 int xioctl (int fh, int request, void *arg);
 
 unsigned char* snapFrame();

I have a problem with building this simple:
Building target: Connect_camera
Invoking: NVCC Linker
/usr/local/cuda-8.0/bin/nvcc --cudart static --relocatable-device-code=false -gencode arch=compute_60,code=compute_60 -gencode arch=compute_60,code=sm_60 -m64 -link -o "Connect_camera" ./main.o ./v4ldevice.o -lopencv_stitching -lopencv_superres -lopencv_videostab -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_dpm -lopencv_face -lopencv_photo -lopencv_freetype -lopencv_fuzzy -lopencv_img_hash -lopencv_line_descriptor -lopencv_optflow -lopencv_reg -lopencv_rgbd -lopencv_saliency -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_surface_matching -lopencv_tracking -lopencv_datasets -lopencv_text -lopencv_dnn -lopencv_plot -lopencv_xfeatures2d -lopencv_shape -lopencv_video -lopencv_ml -lopencv_ximgproc -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_flann -lopencv_xobjdetect -lopencv_imgcodecs -lopencv_objdetect -lopencv_xphoto -lopencv_imgproc -lopencv_core
./main.o: In function cv::String::~String()': /usr/local/include/opencv2/core/cvstd.hpp:648: undefined reference to cv::String::deallocate()'
./main.o: In function cv::String::operator=(cv::String const&)': makefile:58: recipe for target 'Connect_camera' failed /usr/local/include/opencv2/core/cvstd.hpp:656: undefined reference to cv::String::deallocate()'
collect2: error: ld returned 1 exit status
make: *** [Connect_camera] Error 1