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下面这行代码是获取摄像头每帧的时间戳：
double timestamp = cap.get(cv::CAP_PROP_POS_MSEC);
改变帧率的方法是：
cap.set(cv::CAP_PROP_FPS, 30); //帧率改为30
但是实际测试时发现帧率并未被改变，这个可能和VideoCapture cap(cv::CAP_V4L2)有关，cv::CAP_V4L2只是其中一种读取方法，这个参数可能需要和相机采用的驱动方法有关。
编译：
g++ camera_data.cpp -lopencv_core -lopencv_highgui -lopencv_imgcodecs -lopencv_videoio
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>#include <time.h>using namespace std;// OpenCV includes
#include "opencv2/core.hpp"
#include "opencv2/highgui.hpp"
using namespace cv;int main(int argc, const char** argv)
{// 1.创建视频采集对象;VideoCapture cap(cv::CAP_V4L);// 2.打开默认相机;cap.open(0);int curFPS=cap.get(cv::CAP_PROP_FPS);cout<< "FPS: "<< curFPS<<endl;cap.set(cv::CAP_PROP_FPS, 30);int curFpsSet=cap.get(cv::CAP_PROP_FPS);cout<< "set FPS: "<< curFpsSet<<endl;// 3.判断相机是否打开成功;if (!cap.isOpened())return -1;namedWindow("Video", 1);for (;;){// 获取新的一帧;Mat frame;double timestamp = cap.get(cv::CAP_PROP_POS_MSEC);cout<<fixed;cout<<"time: "<< timestamp<<endl;time_t end_time = time(NULL);printf("ctime is %s\n",ctime(&end_time)); //得到日历时间cap >> frame;if (frame.empty())return 0;// 显示新的帧;imshow("Video", frame);// cv::waitKey(1);// 按键退出显示;if (waitKey(3) >= 0) break;}// 5.释放视频采集对象;cap.release();return 0;
}