如何在Visual C ++ 2010或2008中使用OpenCV 2.1访问IP摄像机（compro IP50W）

Question

CvCapture* cam = cvCaptureFromFile("http:\\192.168.0.77");
IplImage* img;
img = cvQueryFrame(cam);

IplImage* current = cvCreateImage(cvGetSize(img),IPL_DEPTH_8U,1);
IplImage* comResult = cvCreateImage(cvGetSize(img),IPL_DEPTH_8U,1); 

double cam_w = cvGetCaptureProperty(cam, CV_CAP_PROP_FRAME_WIDTH);
double cam_h = cvGetCaptureProperty(cam, CV_CAP_PROP_FRAME_HEIGHT);
double fps = 10; 

Answer 1

Read the documentation :

CvCapture* cvCaptureFromFile(const char* filename);

Initializes capturing a video from a file.The function cvCaptureFromFile() allocates and initializes the CvCapture structure for reading the video stream from the specified file. Which codecs and file formats are supported depends on the back end library.

This functions reads from a file ! You need to have a camera connected to your computer to be able to retrieve frames from the camera.

However , if you compiled OpenCV with ffmpeg support you can read from a file in the network, but you must specify the filename in the url.

Notice in the code below that the filename is specified at the end:

CvCapture* camera = cvCaptureFromFile("http://username:pass@cam_address/axis-cgi/mjpg/video.cgi?resolution=640x480&req_fps=30&.mjpg");
if (!camera)
{
    printf("cvCaptureFromFile failed\n");
    exit(1);
}

Always test the return of OpenCV functions. How can you know if the function succeeded if you don't check it, right?!

Answer 2

I found this site helpful to solve this problem

It purpose a simple way to solve the problem regarding handling FFMPEG decode in opencv C++ (windows) and now I am able to retrieve image from IP camera using highgui