OpenCV:VideoCapture :: get(CV_CAP_PROP_FPS)返回0 FPS

Question

我试图从我的相机获取fps,以便我可以将其传递给VideoWriter输出视频.但是,我通过VideoCapture::get(CV_CAP_PROP_FPS)相机调用获得0 fps .如果我硬编码,我的视频可能太慢或太快.

#include "opencv2/opencv.hpp"
#include <stdio.h>
#include <stdlib.h>

using namespace std;
using namespace cv;

int main(int argc, char *argv[])
{
    cv::VideoCapture cap;
    int key = 0;

    if(argc > 1){
        cap.open(string(argv[1]));
    }
    else
    {
        cap.open(CV_CAP_ANY);
    }
    if(!cap.isOpened())
    {
        printf("Error: could not load a camera or video.\n");
    }

    Mat frame;
    cap >> frame;
    waitKey(5);

    namedWindow("video", 1);
    double fps = cap.get(CV_CAP_PROP_FPS);
    CvSize size = cvSize((int)cap.get(CV_CAP_PROP_FRAME_WIDTH),(int)cap.get(CV_CAP_PROP_FRAME_HEIGHT));

    int codec = CV_FOURCC('M', 'J', 'P', 'G');
    if(!codec){ waitKey(0); return 0; }
    std::cout << "CODEC: " << codec << std::endl;
    std::cout << "FPS: " << fps << std::endl;
    VideoWriter v("Hello.avi",-1,fps,size);
    while(key != 'q'){
        cap >> frame;
        if(!frame.data)
        {
            printf("Error: no frame data.\n");
            break;
        }
        if(frame.empty()){ break; }
        v << frame;
        imshow("video", frame);
        key = waitKey(5);
    }
    return(0);
}

如何才能VideoCapture::get(CV_CAP_PROP_FPS)返回正确的fps或VideoWriter为所有网络摄像头提供通用的fps ？

Answer 1

据我所知，CV_CAP_PROP_FPS 仅适用于视频。如果您想从网络摄像头捕获视频数据，您必须自己正确计时。例如，使用计时器每 40 毫秒从网络摄像头捕获一帧，然后保存为 25 fps 视频。