无法从网络摄像头抓取帧 [英] Can't grab frame from webcamera

问题描述

我正在将OpenCV 2.4.6，VS2010与Windows 7 64位一起使用.我无法从相机中抓取相框.下面的代码对于avi文件工作正常，但无法从相机捕获.谁能帮我，如何捕捉框架?在此先感谢....

I am using OpenCV 2.4.6, VS2010 with Windows 7 64 bit. I could not grab frame from the camera. The code below is working fine for avi file, but not working to capture from camera. Can anyone help me, how can I capture the frame? Thanks in advance.......

这部分实际上是问题:

bool bSuccess = cap.read(frame); //从视频中读取新帧

bool bSuccess = cap.read(frame); // read a new frame from video

    if (!bSuccess) //if not success, break loop
    {
        cout << "Cannot read a frame from video file" << endl;
        break;
    }

完整的源代码:

#include "opencv2/highgui/highgui.hpp"
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char* argv[])
{
    VideoCapture cap(0); // open the video camera no. 0

    if(!cap.isOpened())  // if not success, exit program
    {
        cout << "Cannot open the video file" << endl;
        return -1;
    }

    double dWidth = cap.get(CV_CAP_PROP_FRAME_WIDTH); //get the width of frames of the video
    double dHeight = cap.get(CV_CAP_PROP_FRAME_HEIGHT); //get the height of frames of the video

    cout << "Frame size : " << dWidth << " x " << dHeight << endl;

    namedWindow("MyVideo",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"

    while(1)
    {
        Mat frame;

        bool bSuccess = cap.read(frame); // read a new frame from video

        if (!bSuccess) //if not success, break loop
        {
            cout << "Cannot read a frame from video file" << endl;
            break;
        }

        imshow("MyVideo", frame); //show the frame in "MyVideo" window

        if(waitKey(30) == 27) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
        {
            cout << "esc key is pressed by user" << endl;
            break; 
        }
    }
    return 0;
}

推荐答案

在使用while循环之前，您应该阅读第一帧:

Mat frame;
cap.read(frame); 
while(1)
{
    bool bSuccess = cap.read(frame); // read a new frame from video

    if (!bSuccess) //if not success, break loop
    {
        cout << "Cannot read a frame from video file" << endl;
        break;
    }

    imshow("MyVideo", frame); //show the frame in "MyVideo" window

    if(waitKey(30) == 27) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
    {
        cout << "esc key is pressed by user" << endl;
        break; 
    }
}

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