C语言打开UVC摄像头并显示

在C语言中打开UVC摄像头并显示，可以使用Video4Linux2（V4L2）接口来操作。

下面是一个简单的示例代码：

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

#define BUFFER_COUNT 4

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

int main(int argc, char **argv) {
    int fd;
    struct v4l2_capability cap;
    struct v4l2_format fmt;
    struct v4l2_requestbuffers req;
    struct v4l2_buffer buf;
    enum v4l2_buf_type type;
    struct buffer *buffers;
    int i, n_buffers;

    fd = open("/dev/video0", O_RDWR);
    if (fd == -1) {
        perror("open");
        return EXIT_FAILURE;
    }

    if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
        perror("VIDIOC_QUERYCAP");
        return EXIT_FAILURE;
    }

    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        fprintf(stderr, "The device does not support video capture.\n");
        return EXIT_FAILURE;
    }

    memset(&fmt, 0, sizeof(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;
    if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
        perror("VIDIOC_S_FMT");
        return EXIT_FAILURE;
    }

    memset(&req, 0, sizeof(req));
    req.count = BUFFER_COUNT;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;
    if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
        perror("VIDIOC_REQBUFS");
        return EXIT_FAILURE;
    }

    buffers = calloc(req.count, sizeof(struct buffer));
    if (!buffers) {
        perror("calloc");
        return EXIT_FAILURE;
    }

    for (i = 0; i < req.count; i++) {
        memset(&buf, 0, sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;
        if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1) {
            perror("VIDIOC_QUERYBUF");
            return EXIT_FAILURE;
        }

        buffers[i].length = buf.length;
        buffers[i].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
        if (buffers[i].start == MAP_FAILED) {
            perror("mmap");
            return EXIT_FAILURE;
        }
    }

    for (i = 0; i < req.count; i++) {
        memset(&buf, 0, sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;
        if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
            perror("VIDIOC_QBUF");
            return EXIT_FAILURE;
        }
    }

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (ioctl(fd, VIDIOC_STREAMON, &type) == -1) {
        perror("VIDIOC_STREAMON");
        return EXIT_FAILURE;
    }

    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 (r == -1) {
            perror("select");
            return EXIT_FAILURE;
        }

        if (r == 0) {
            fprintf(stderr, "select timeout\n");
            return EXIT_FAILURE;
        }

        memset(&buf, 0, sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
            perror("VIDIOC_DQBUF");
            return EXIT_FAILURE;
        }

        // process the frame here (buffers[buf.index].start)

        if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
            perror("VIDIOC_QBUF");
            return EXIT_FAILURE;
        }
    }

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if (ioctl(fd, VIDIOC_STREAMOFF, &type) == -1) {
        perror("VIDIOC_STREAMOFF");
        return EXIT_FAILURE;
    }

    for (i = 0; i < req.count; i++) {
        if (munmap(buffers[i].start, buffers[i].length) == -1) {
            perror("munmap");
            return EXIT_FAILURE;
        }
    }

    free(buffers);

    if (close(fd) == -1) {
        perror("close");
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}

该代码使用mmap（内存映射）方式获取摄像头数据，并使用VIDIOC_DQBUF和VIDIOC_QBUF命令从缓冲区中获取和放回帧数据。在这里，您需要实现处理帧的代码。