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You don't need to release the image (cvReleaseImage(&ipl) because cvQueryFrame owns it.
Somewhere

Quoted

cvQueryFrame

Grabs and returns a frame from camera or AVI
IplImage* cvQueryFrame( CvCapture* capture );
capture
CvCapture representing camera or AVI file.

The function cvQueryFrame grabs a frame from camera or AVI and returns the pointer to grabbed image. Actually this function just successively calls cvGrabFrame and cvRetrieveFrame. The returned image should not be released by the user.

#include<QtCore/QCoreApplication>#include<cv.h>
#include<highgui.h>
#include<stdio.h>
#include<string.h>
intmain(intargc,char*argv[])
{
QCoreApplicationa(argc,argv);
CvCapture*AVIfile=NULL;
cvCaptureFromFile("C:\\OpenCV2.2\\samples\\cpp\\Qt_sample\\cube4.avi");
if(!AVIfile){
return1;
}
cvReleaseCapture(&AVIfile);
returna.exec();
}
This code just builds fine, but when I tried to run it, the application is crashed. When tried to debug by setting break points, I could notice that immediately after the cvCaptureFromFile method is invoked, some assembly code shows up, and a message box comes in telling that "Inferior stopped because it received a signal from the operating system. Signal Name : SIGSEGV. Signal meaning: Segmentation fault. My .pro file is

QT += core


QT -= gui

TARGET = Dec28C1
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp
INCLUDEPATH += C:\OpenCV2.2\include\opencv C:\OpenCV2.2\include
LIBS += C:\OpenCV2.2\lib\*.lib

I am struggling with this since 1st January. I could compile and run some other programs well. But don't know. What to do with this error. Please help me.