使用V4L2获取摄像头的信息

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V4L2全称是Video for Linux 2，通过它可以驱动摄像头。

在Ubuntu中，已经内置了V4L2，因此不需要安装多余的东西。在WRTnode中，如果你需要使用V4L2，需要这样： 

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Libraries  --->    libv4l

然后直接上代码： 

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#include <stdio.h>
#include <fcntl.h>
#include <linux/videodev2.h>

char videodevice[] = "/dev/video0";
void printFrameInterval(int fd, unsigned int fmt, unsigned int width, unsigned int height)
{
    struct v4l2_frmivalenum frmival;
    memset(&frmival,0,sizeof(frmival));
    frmival.pixel_format = fmt;
    frmival.width = width;
    frmival.height = height;
    while (ioctl(fd, VIDIOC_ENUM_FRAMEINTERVALS, &frmival) == 0) 
    {
        if (frmival.type == V4L2_FRMIVAL_TYPE_DISCRETE) 
            printf("[%dx%d] %f fps\n", width, height, 1.0*frmival.discrete.denominator/frmival.discrete.numerator);
        else
            printf("[%dx%d] [%f,%f] fps\n", width, height, 1.0*frmival.stepwise.max.denominator/frmival.stepwise.max.numerator, 1.0*frmival.stepwise.min.denominator/frmival.stepwise.min.numerator);
        frmival.index++;    
    }
}
int main()
{
	//打开摄像头设备
	int fd = -1;
	fd = open (videodevice, O_RDWR, 0);
	if(fd<0){
		printf("failed to open\n");
		return -1;
	}
	printf("打开摄像头设备成功，%s\n", videodevice);

	//查询摄像头信息，VIDIOC_QUERYCAP
	printf("------------\n");
	struct v4l2_capability cap;
	ioctl (fd, VIDIOC_QUERYCAP, &cap);
	printf("Driver Name:%s\nCard Name:%s\nBus info:%s\nDriver Version:%u.%u.%u\n\n",cap.driver,cap.card,cap.bus_info,(cap.version>>16)&0XFF, (cap.version>>8)&0XFF,cap.version&0XFF);

	//查询摄像头视频格式，VIDIOC_ENUM_FMT
	printf("------------\n");
	struct v4l2_fmtdesc fmtdesc;
	fmtdesc.index=0;
	fmtdesc.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;
	printf("Supportformat:\n");
	while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc)!=-1)  
	{
		printf("\t%d.%c%c%c%c\t%s\n",fmtdesc.index+1,fmtdesc.pixelformat & 0xFF, (fmtdesc.pixelformat >> 8) & 0xFF,(fmtdesc.pixelformat >> 16) & 0xFF, (fmtdesc.pixelformat >> 24) & 0xFF,fmtdesc.description);
		fmtdesc.index++;
	}

	v4l2_close(fd);
	return 0;
}
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gcc test.c -o test -lv4l2
./test

这里我获取了三个摄像头的信息。