IMX8 + Linux + 海康威视 实现获取摄像头 源码

获取海康威视摄像头的源码，需要先了解一下摄像头的型号和接口类型。如果是USB接口的摄像头，可以使用V4L2(UVC)驱动来进行操作。如果是CSI接口的摄像头，需要根据具体的型号和规格书来开发对应的驱动程序。以下是一个使用V4L2驱动的示例程序：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>

#define CAMERA_DEVICE "/dev/video0"
#define CAPTURE_FILE "frame.raw"
#define IMAGE_WIDTH 640
#define IMAGE_HEIGHT 480

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

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;
}

static void process_image(const void *p, int size)
{
    FILE *fp;
    fp = fopen(CAPTURE_FILE, "wb");
    if (fp) {
        fwrite(p, size, 1, fp);
        fclose(fp);
    }
}

static int read_frame(int fd, struct buffer *buffers)
{
    struct v4l2_buffer buf;

    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");
        }
    }

    process_image(buffers[buf.index].start, buf.bytesused);

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

    return 1;
}

static void mainloop(int fd, struct buffer *buffers)
{
    unsigned int count;
    count = 100;

    while (count-- > 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(fd, buffers))
                break;
        }
    }
}

static void stop_capturing(int fd)
{
    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(int fd, struct buffer *buffers)
{
    unsigned int i;
    enum v4l2_buf_type type;

    for (i = 0; i < 4; ++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_QUERYBUF, &buf))
            errno_exit("VIDIOC_QUERYBUF");

        buffers[i].length = buf.length;
        buffers[i].start = mmap(NULL /* start anywhere */, buf.length,
                                PROT_READ | PROT_WRITE /* required */,
                                MAP_SHARED /* recommended */, fd, buf.m.offset);

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

    for (i = 0; i < 4; ++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(struct buffer *buffers)
{
    unsigned int i;

    for (i = 0; i < 4; ++i)
        if (-1 == munmap(buffers[i].start, buffers[i].length))
            errno_exit("munmap");
}

static void init_mmap(int fd, struct buffer **buffers, unsigned int *n_buffers)
{
    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", CAMERA_DEVICE);
            exit(EXIT_FAILURE);
        } else {
            errno_exit("VIDIOC_REQBUFS");
        }
    }

    if (req.count < 2) {
        fprintf(stderr, "Insufficient buffer memory on %s\n",
                CAMERA_DEVICE);
        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 /* 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");
    }
}

static void init_device(int fd)
{
    struct v4l2_capability cap;
    struct v4l2_format fmt;

    if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
        if (EINVAL == errno) {
            fprintf(stderr, "%s is no V4L2 device\n", CAMERA_DEVICE);
            exit(EXIT_FAILURE);
        } else {
            errno_exit("VIDIOC_QUERYCAP");
        }
    }

    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        fprintf(stderr, "%s is no video capture device\n", CAMERA_DEVICE);
        exit(EXIT_FAILURE);
    }

    if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
        fprintf(stderr, "%s does not support streaming i/o\n", CAMERA_DEVICE);
        exit(EXIT_FAILURE);
    }

    CLEAR(fmt);

    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = IMAGE_WIDTH;
    fmt.fmt.pix.height = IMAGE_HEIGHT;
    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");

    if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_YUYV) {
        fprintf(stderr, "Libv4l only supports V4L2_PIX_FMT_YUYV format\n");
        exit(EXIT_FAILURE);
    }
}

int main(int argc, char *argv[])
{
    struct buffer *buffers;
    unsigned int n_buffers;

    int fd = open(CAMERA_DEVICE, O_RDWR | O_NONBLOCK, 0);
    if (-1 == fd) {
        fprintf(stderr, "Cannot open %s\n", CAMERA_DEVICE);
        exit(EXIT_FAILURE);
    }

    init_device(fd);
    init_mmap(fd, &buffers, &n_buffers);
    start_capturing(fd, buffers);
    mainloop(fd, buffers);
    stop_capturing(fd);
    uninit_device(buffers);

    close(fd);

    return 0;
}

这个程序会从摄像头中获取视频流，并将每一帧保存到文件中。您需要根据自己的需求进行修改。需要注意的是，这个程序只适用于使用V4L2驱动的摄像头，如果您使用的是CSI接口的摄像头，需要开发对应的驱动程序。