OpenCV:VideoCapture :: get(CV_CAP_PROP_FPS)返回0 FPS [英] OpenCV: VideoCapture::get(CV_CAP_PROP_FPS) returns 0 FPS
问题描述
我想从我的相机获取fps,以便我可以将其传递到 VideoWriter
以输出视频。然而,我得到0 fps通过调用 VideoCapture :: get(CV_CAP_PROP_FPS)
从我的相机。如果我硬编码,我的视频可能太慢或太快。
I am trying to get the fps from my camera so that I can pass it to the VideoWriter
for outputting the video. However, I am getting 0 fps by calling VideoCapture::get(CV_CAP_PROP_FPS)
from my camera. If I hardcode it, my video may be too slow or too fast.
#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);
}
如何获得 VideoCapture :: get(CV_CAP_PROP_FPS )
以返回正确的fps或给所有网络摄像机普遍使用的 VideoWriter
提供fps?
How can I get VideoCapture::get(CV_CAP_PROP_FPS)
to return the right fps or give a fps to the VideoWriter
that works universally for all webcams?
推荐答案
CV_CAP_PROP_FPS只适用于我所知道的视频。如果你想从网络摄像头捕获视频数据,你必须自己正确的时间。例如,使用计时器每40ms从网络摄像头捕获一帧,然后保存为25fps视频。
CV_CAP_PROP_FPS only works on videos as far as I know. If you want to capture video data from a webcam you have to time it correctly yourself. For example use a timer to capture a frame from the webcam every 40ms and then save as 25fps video.
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