OpenCV -- 打开视频

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1、OpenCV打开摄像头

2、打开视频流文件

3、VideoCapture关闭和释放资源

4、读取一帧视频

5、获取视频、相机属性

播放时间 秒 = 总帧数/帧率

6、设置视频的播放进度

7、打开视频代码演示

    VideoCapture video;
	video.open("1.mp4");
	if (!video.isOpened())
	{
		cout << "open video failed!" << endl;
		getchar();
		return -1;
	}

	cout << "open video success!" << endl;
	namedWindow("video");
	Mat frame;
	int fps = video.get(CAP_PROP_FPS);  // 获取帧率
	
	int s = 30;
	if (fps!=0)
	{
		s = 1000 / fps;
	}

	cout << "fps is " << fps << endl;
	int fcount = video.get(CAP_PROP_FRAME_COUNT);
	cout << "total frame is " << fcount << endl;
	cout << "total second is " << fcount / fps;

	for (;;)
	{
		//if (!video.read(frame))
		//{
		//	break;
		//}
		//读帧，解码
		if (!video.grab())
		{
			break;
		}
		//转换颜色格式
		if (!video.retrieve(frame))
		{
			break;
		}
		int cur = video.get(CAP_PROP_POS_FRAMES);  // 获取视频当前属性
		if (cur > fps * 3) 
		{
			video.set(CAP_PROP_POS_FRAMES, 0);  // 3秒后回到开始位置
			continue;
		}
		imshow("video", frame);
		waitKey(s);
	}
	getchar();

8、VideoWriter 创建视频文件

操作完成之后，需要主动关闭；

9、VideoWriter

    VideoCapture cam(0);
	namedWindow("cam");
	if (!cam.isOpened()) 
	{
		cout << "cam open failed!" << endl;
		getchar();
		return -1;
	}
	cout << "cam open success!" << endl;
	Mat img;
	VideoWriter vw;
	int fps = cam.get(CAP_PROP_FPS);
	if (fps <= 0)fps = 25;

	vw.open("out.avi", VideoWriter::fourcc('X', '2', '6', '4'), fps, 
		Size(cam.get(CAP_PROP_FRAME_WIDTH), cam.get(CAP_PROP_FRAME_HEIGHT)));

	if (!vw.isOpened())
	{
		cout << "VideoWriter open failed!" << endl;
		getchar();
		return -2;
	}
	cout << "VideoWriter open success!" << endl;
	while (1)
	{
		cam.read(img);
		if (img.empty())break;
		imshow("cam", img);
		vw.write(img);
		if (waitKey(5) == 'q')break;
	}

	waitKey(0);

10、FFmpeg工具的使用

1）抽取音频

2）剪切音频

3）音频合并