main.c

// gcc -o main main.c -lv4l2
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libv4l2.h>
#include <linux/videodev2.h>


int main(int argc, char* argv[]) {

    char* device = "/dev/video0";
    int width = 624;
    int height = 480;
    int opt = 0;
    while ((opt = getopt(argc, argv, "d:w:h:")) != -1) {
        switch (opt) {
        case 'd': { device = optarg; } break;
        case 'w': { width = atoi(optarg); } break;
        case 'h': { height = atoi(optarg); } break;
        default: { fprintf(stderr, "error: \'%c\' \'%c\'\n", opt, optopt); return 1;}
        }
    }

    int fd = v4l2_open(device, O_RDWR);
    if (fd < 0) {
        perror("error: v4l2_open");
        return 1;
    }

    struct v4l2_format fmt;
    memset(&fmt, 0, sizeof(fmt));
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = width;
    fmt.fmt.pix.height = height;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
    fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;

    int res = v4l2_ioctl(fd, VIDIOC_S_FMT, &fmt);
    if (res != 0) {
        perror("error");
        return 1;
    }

    if (fmt.fmt.pix.width != width ||
        fmt.fmt.pix.height != height ||
        fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) {
        printf("unexpected format\n");
        return 1;
    }

    puts("[format]");
    printf("width                : %u\n", fmt.fmt.pix.width);
    printf("height               : %u\n", fmt.fmt.pix.height);
    printf("bytesperline         : %u\n", fmt.fmt.pix.bytesperline);
    printf("sizeimage            : %u\n", fmt.fmt.pix.sizeimage);
    printf("bytesperline * height: %u\n", fmt.fmt.pix.bytesperline * fmt.fmt.pix.height);


    v4l2_close(fd);

    return 0;
}