How to extract Frames from AVI video

edit

Try this.(press "f" button to save frame)
it's your code with some changes!

#include<opencv\cv.h>
#include<opencv\highgui.h>
#include<opencv\ml.h>
#include<opencv\cxcore.h>
#include<fstream>



int main( int argc, char** argv ) {
cvNamedWindow( "DisplayVideo", CV_WINDOW_AUTOSIZE );
CvCapture* capture = cvCreateFileCapture( argv[1] );
IplImage* frame;
int num=0;
char s [20];
while(1) {
num++;
frame = cvQueryFrame( capture );
if( !frame ) break;
cvShowImage( "DisplayVideo", frame );
char c = cvWaitKey(33);
if( c == 27 ) break;
if (c == 'f')
{
sprintf(s,"frame%d.jpg",num);
cvSaveImage(s,frame);

}
}
cvReleaseCapture( &capture );
cvDestroyWindow("DisplayVideo" );
}