opencv打开USB摄像头

#include <thread>

Mat gImage;
#define FRAME_RATE 30  //默认帧率30

/* 默认分辨率720p */
#define DEFAULT_WIDTH 1280
#define DEFAULT_HEIGHT 720


/******************************USB摄像头  *******************************/
void threadUsbCapture()
{
	VideoCapture cap;


	prctl(PR_SET_NAME,"threadOpencvCapture");
	cap.open(4);

	/* opencv默认是640*480，这里修改成720p */
	cap.set(CAP_PROP_FRAME_WIDTH, DEFAULT_WIDTH);
	cap.set(CAP_PROP_FRAME_HEIGHT, DEFAULT_HEIGHT);

	while(1)
	{
		cap >> gImage;
		usleep(1000 * 1000 / FRAME_RATE);
	}
}


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

	/* 初始化显示窗口 */
	const string wintitle = "camera";
	namedWindow(wintitle);

	thread t(threadUsbCapture);
	while (1)
	{
		/* 获取video0的数据 */
		if (gImage.empty())
			continue;

		/* 显示图片 */
		imshow(wintitle, gImage);
		/* 等待按键 */
		if (waitKey(30) >= 0)
		{
			break;
		}
	}
}