Memory leaks getting sub-images from video (cvGetSubRect)

i'm trying to do video windowing that is:

show all frames from a video and also some sub-image from each frame. This sub-image can change size and be taken from a different position of the original frame.

So , the code i've written does basically this:

1. cvQueryFrame to get a new image from the video
2. Create a new IplImage (img) with sub-image dimensions ( window.height,window.width)
3. Create a new Cvmat (mat) with sub-image dimensions ( window.height,window.width)
4. CvGetSubRect(originalImage,mat,window) seizes the sub-image
5. transform Mat (cvMat) to img (IplImage) using cvGetImage

my problem is that for each frame i create new IplImage and cvMat which take a lot of memory and when i try to free the allocated memory I get a segmentation fault or in the case of the CvMat the allocated space does not get free (valgrind keeps telling me its definetly lost space).

the following code does it:

int 
main(void){

    CvCapture* capture;

    CvRect window;
    CvMat * tmp;

    //window size
    window.x=0;window.y=0;window.height=100;window.width=100;

    IplImage * src=NULL,*bk=NULL,* sub=NULL;

    capture=cvCreateFileCapture( "somevideo.wmv");

    while((src=cvQueryFrame(capture))!=NULL){
        cvShowImage("common",src);

        //get sub-image
        sub=cvCreateImage(cvSize(window.height,window.width),8,3);
        tmp =cvCreateMat(window.height, window.width,CV_8UC1);
        cvGetSubRect(src, tmp , window);
        sub=cvGetImage(tmp, sub);

        cvShowImage("Window",sub);

        //free space
        if(bk!=NULL)
            cvReleaseImage(&bk);
        bk=sub;

        cvReleaseMat(&tmp);
        cvWaitKey(20);

        //window dimensions changes
        window.width++;
        window.height++;
    }
}

cvReleaseMat(&tmp); does not seem to have any effect on the total amount of lost memory, valgrind reports the same amount of "definetly lost" memory if i 开发者_StackOverflowcomment or uncomment this line.

cvReleaseImage(&bk); produces a segmentation fault. notice i'm trying to free the previous sub-frame which i'm backing up in the bk variable. If i comment this line the program runs smoothly but with lots of memory leaks

i'm using ubuntu 9.10 with opencv 2.0 .

I really need to get rid of memory leaks, can anyone explain me how to correct this or even better how to correctly perform image windowing?

Thank you

Someone report the same problem as a bug in the library. http://sourceforge.net/tracker/index.php?func=detail&aid=3025393&group_id=22870&atid=376677

I solved it by using ROI in the image instead of cvGetSubRect, that way you avoid to alloc another mat.