OpenCV & Virsual C++: save Frame data from Camera and then save to Jpg

I am an OpenCV and C++ beginner. I've got a problem with my student project.My Tutor wants to grab frames from a Camera and save the grabbed frames into jpg. So first I used "cvCreateCameraCapture，cvQueryFrame，cvSaveImage" and it worded ok. But the frame is relative big,about 2500x2000,and it takes about 1 second to save one Frame. But my Tutor requires at least to save 10 Frames per second.

Then I came out the ideas to save raw data first and after grabbing process I can save them into Jpg. So I wrote following test code.But the problem is that all the saved Images are the same and it seems they are just from the data of the last grabbed frame.I guess the problem is about my poor knowledge of c++ especially pointers.So I really 开发者_运维问答hope to get help here.

Thanks in advance!

void COpenCVDuoArryTestDlg::OnBnClickedButton1()
{
IplImage* m_Frame=NULL;
TRACE("m_Frame initialed");
CvCapture * m_Video=NULL;
m_Video=cvCreateCameraCapture(0);
IplImage**Temp_Frame= (IplImage**)new IplImage*[100]; 
for(int j=0;j<100;j++){

Temp_Frame[j]= new IplImage [112];

}
TRACE("Tempt_Frame initialed\n");

cvNamedWindow("video",1);
int t=0;

while(m_Frame=cvQueryFrame(m_Video)){ 

    for(int k=0;k<m_Frame->nSize;k++){
Temp_Frame[t][k]= m_Frame[k];

    }

cvWaitKey(30);
t++;

if(t==100){
break;
}

}


for(int i=0;i<30;i++){
CString ImagesName;

ImagesName.Format(_T("Image%.3d.jpg"),i);

if(cvWaitKey(20)==27) {
break;
}
else{

cvSaveImage(ImagesName, Temp_Frame[i]);

}    
}    

cvReleaseCapture(&m_Video);
cvDestroyWindow("video");
TRACE("cvDestroy works\n");

delete []Temp_Frame;
}

---

If you use C++, why don't you use the C++ opencv interface? The reason you get N times the same image is that the capture reuses the memory for each frame, if you want to store the frames you need to copy them. Example for the C++ interface:

#include <vector>
#include "cv.h"
#include "highgui.h"

using namespace cv;

int main(int, char**)
{
    VideoCapture cap(0); // open the default camera
    if(!cap.isOpened())  // check if we succeeded
        return -1;

    Mat edges;
    namedWindow("image",1);
    std::vector<cv::Mat> images(100);
    for(int i = 0; i < 100;++i) { 
        // this is optional, preallocation so there's no allocation
        // during capture
        images[i].create(480, 640, CV_8UC3);
    }
    for(int i = 0; i < 100;++i)
    {
        Mat frame;
        cap >> frame; // get a new frame from camera
        frame.copyTo(images[i]);
    }
    cap.release();
    for(int i = 0; i < 100;++i)
    {
        imshow("image", images[i]);
        if(waitKey(30) >= 0) break;
    }
    // the camera will be deinitialized automatically in VideoCapture destructor
    return 0;
}

---

Do you have a multicore/multiple CPU system? Then you could farm out the 1second tasks across 16cores and save 16frames/second !

Or you could write your own optimized jpeg routine on the GPU in Cuda/OpenCL.

If you need it to run for longer you could dump the raw image data to disk, then read it back in later and convert to jpeg. 5Mpixel * 3color * 10fps is 150Mb/s (thanks etarion!) which you can do with two disks and windows Raid.

edit: If you only need to do 10frames then just buffer them in memory and then write them out as the other answer shows.

---

Since you already know how to retrieve a frame, check this answer:

openCV: How to split a video into image sequence?

This question is a little different because it retrieves frames from an AVI file instead of a webcam, but the way to save a frame to the disk is the same!