OpenCV 无法从网络摄像头捕获帧

Question

我在 VS2010 中使用 OpenCV 2.4.6。

我认为我的网络摄像头无法捕获帧。当我执行它成功构建的代码时，但我没有得到输出。我想，当我检查if(!bSuccess) 时，它被执行并且无法从网络摄像头捕获帧。

我该如何解决这个问题？我的代码如下：

#include "opencv2/highgui/highgui.hpp" #include 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 &lt&lt "Cannot open the video file" &lt&lt 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 &lt&lt "Frame size : " &lt&lt dWidth &lt&lt " x " &lt&lt dHeight &lt&lt 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 &lt&lt "Cannot read a frame from video file" &lt&lt endl; break; } imshow("MyVideo", frame); //show the frame in "MyVideo" window if (waitKey(30) == 27) { cout &lt&lt "esc key is pressed by user" &lt&lt endl; break; } } return 0; }

Answer 1

添加此行cap.retrieve(frame);

在bool bSuccess = cap.read(frame);行之前

Answer 2

修复 VideoCapture 失败

在一些 openCV 库中，VideoCapture cap(0);bool bSuccess = cap.read(frame); 将首先返回一个0。因此，对于while(1) 循环，它将在第一次迭代时失败。所以你需要在进入无限循环之前运行一次cap.read(frame); 行

#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 cam" << 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"

    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 stream" << 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;

}

Answer 3

尝试不使用这部分代码：

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"

或在获取或设置相机属性之前尝试从相机中获取至少一帧 - 我认为在获取第一帧之前，opencv 中的 Windows 相机并未完全优化。

或者，您可以尝试使用不同的 API - 请参阅此处的答案：OpenCV on Mac is not opening USB web camera

Answer 4

不仅是第一帧，还可以跳过许多其他帧；-)

opencv 2.4.9 视觉工作室 10

#include <iostream>
#include <opencv2\core\core.hpp>
#include <opencv2\highgui\highgui.hpp>

using namespace std;
using namespace cv;

int main()
{
	VideoCapture webcam_0(0);                    //open stream
	if(!webcam_0.isOpened())
	{
		cout << "error: cannot open stream between webcam_0 and application" << endl;
		waitKey(0);
		return -1;
	}

	Mat frame;                                   //Mat header for frame storing from webcam_0
	int i = 0;                                   //index, we use it for testing
	
	while ((i++ < 100) && !webcam_0.read(frame)) //skip unread frames
	{
		cout << "frame " << i << " skipped" << endl;
	}

	if (i >= 100)                                //check webcam_0 failure
	{
		cout << "cannot read frames from webcam_0, check drivers" << endl;
		waitKey(0);
		return -1;
	} else
	{
		cout << "cam is ready" << endl;
	}

	char * window_name = "webcam_0 test; press \"ESC\" to exit";
	namedWindow(window_name, CV_WINDOW_AUTOSIZE);//make new window
	imshow(window_name, frame);                  //output 1st successfully read frame
	waitKey(10);
	
	while(1)                                     //reading frames from webcam_0
	{
		if(!webcam_0.read(frame))
		{
			cout << "cannot get frame from webcam_0, check drivers" << endl;
			waitKey(0);
			return -1;
		}
		imshow(window_name, frame);

		if (waitKey(10) == 27)                   //check if ESC is pressed
		{
			cout << "bye!" << endl;
			waitKey(0);
			break;
		}
	}
	return 0;
}

Answer 5

试试下面的代码：

#include "stdafx.h"
#include "highgui\highgui.hpp"  

using namespace cv;


void main()
{
    Mat Frame;

    VideoCapture cap(0);  // change the number to 1 for an external USB webcam

    while(1)
    {
        cap >> Frame;
        imshow("Camera Feed", Frame);

        if (waitKey(10) == 27)  return;
    }
}

Answer 6

在所有类似于下面提到的情况下删除“cv_”：

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);

它对我有用。