Save Image Sequence real time,but cannot save Consecutive pictures ，why?

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#include <opencv2/opencv.hpp>

#include<time.h>
int main() 
{
                      char file[256];  
        time_t mytime;
        mytime = time(NULL);
        struct tm tm = *localtime(&mytime);
        printf("now: %d-%d-%d %d:%d:%d\n", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);

        CvCapture* capture = cvCaptureFromCAM( CV_CAP_ANY );


       if ( !capture ) {
      fprintf( stderr, "ERROR: capture is NULL \n" );
      getchar();
      return -1;

}

 cvNamedWindow( "mywindow", CV_WINDOW_AUTOSIZE );



while ( 1 ) {
  IplImage* frame = cvQueryFrame(capture);
 if ( !frame ) {

   fprintf( stderr, "ERROR: frame is null...\n" );

   break;
 }
 cvShowImage( "mywindow", frame );

 sprintf(file,"%s%d%d%d_%d%d%d%d.jpg\n","D:/Projects/vs2010/text11/", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec); 

 cvSaveImage(file, frame,0);

 //sleep(2);
 // Do not release the frame!
 //If ESC key pressed, Key=0x10001B under OpenCV 0.9.7(linux version),
 //remove higher bits using AND operator
 if ( (cvWaitKey(10) & 255) == 27 ) break;

}

  cvReleaseCapture( &capture );
  cvDestroyWindow( "mywindow" );
  return 0;

}