Which OS are you using ? im adding an example to open /dev/video0 and capture a frame on linux using the built in V4L2 (I am unfamiliar with the windows alternative)

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

int main() {
    int fd = open("/dev/video0", O_RDWR);  // Open the video device
    if (fd == -1) {
        perror("Opening video device");
        return 1;
    }

    struct v4l2_capability cap;
    if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
        perror("Querying Capabilities");
        return 1;
    }

    struct v4l2_format 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_MJPEG;  // Set format to MJPEG
    fmt.fmt.pix.field = V4L2_FIELD_NONE;
    
    if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
        perror("Setting Pixel Format");
        return 1;
    }

    struct v4l2_requestbuffers req;
    req.count = 1;  // Request a single buffer
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;

    if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
        perror("Requesting Buffer");
        return 1;
    }

    struct v4l2_buffer buf;
    memset(&buf, 0, sizeof(buf));
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = 0;

    if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1) {
        perror("Querying Buffer");
        return 1;
    }

    void* buffer = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);

    if (buffer == MAP_FAILED) {
        perror("mmap");
        return 1;
    }

    if (ioctl(fd, VIDIOC_STREAMON, &buf.type) == -1) {
        perror("Stream On");
        return 1;
    }

    // Queue the buffer
    if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
        perror("Queue Buffer");
        return 1;
    }

    // Dequeue the buffer
    if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
        perror("Dequeue Buffer");
        return 1;
    }

    FILE* out = fopen("capture.jpg", "wb");
    if (!out) {
        perror("Cannot open image");
        return 1;
    }

    fwrite(buffer, buf.bytesused, 1, out);  // Save buffer to JPEG
    fclose(out);

    munmap(buffer, buf.length);
    close(fd);

    return 0;
}

Ive used this for a MATLAB project, to capture and analyse binning of pixels on a certain display and camera. I hope it helps