CODEWITHSUNDEEP
c++debuggingvideomemory-leaksopencv
fdh
fdh

Reputation: 5354

A memory leak in cvCaptureFromCAM?

It turns out that using cvCaptureFromCAM creates a memory in initialization. Usage of cvCaptureFromCAM creates a 48 byte memory leak of a NSAutoreleasePool object. I initially thought my program had a bug, but when replaced with a much simpler program, the memory leak still occurs.

For example: 

#include <opencv2/opencv.hpp>
int main()
{
   IplImage *frame = 0;
   CvCapture *capture = cvCaptureFromCAM (-1); //leak occurs on this line  
   //using 0 instead of -1 creates a leak too

   cvNamedWindow ("Output", CV_WINDOW_AUTOSIZE);

   while (1)
   {
      frame = cvQueryFrame (capture);
      cvShowImage ("Output", frame);
   }

   cvDestroyAllWindows ();
   cvReleaseCapture (&capture);

   return 0;
}

I am using Xcode Leaks to find memory leaks and am obviously using the Xcode IDE on Mac OS X 10.6. Does anyone know a solution to the leak? Am I doing something wrong or it a bug in OpenCV or a problem with my computer? I double checked my code and the OpenCV code but couldn't really find a problem. The memory leak is a one time thing - it doesn't keep building. However I am not comfortable with leaving ANY leaks in my program. Does anyone have any suggestions?

Upvotes: 2

Views: 963

Answers (3)

wrjohns
wrjohns

Reputation: 494

I was able to find the memory leaks with cv::VideoCapture and NSAutoreleasePool. The problems are all in modules/highgui/src/cap_qtkit.mm.

I found about 3 examples of the following:

  1. An NSAutoreleasePool is allocated.
  2. A method exited early (this code very liberally uses early returns out of functions)
  3. Some of these returns do not clean up after themselves when using an early return

So the fix is for every occurrence of [[NSAutoreleasePool alloc] init], check the remainder of the function for a return. If there isn't a statement along the lines of [localpool drain] (or whatever variable name was used in the alloc) just prior to the return, then add one in.

There are 2 other source files in highgui that use NSAutoreleasePool that may have similar issues, but I don't use them and haven't checked.

Once I fixed this issue, my memory leaks went away. Again, I'm using OpenCV 2.4.2.

Upvotes: 0

fdh
fdh

Reputation: 5354

I was unfortunately unable to find the leak in cvCaptureFromCAM, so I switched to the C++ interface and used a VideoCapture object, which appears to be free of leaks.

Upvotes: 1

sam
sam

Reputation: 1397

i think the problem is this part 

while (1)
{
   frame = cvQueryFrame (capture);
   cvShowImage ("Output", frame);
}

in my idea you have to change this unlimited WHILE to FOR and for have to be fix memory size and after for you have to use 

Release();
 or 
EndQuery();

i do this method like this 

 while (1)
 {
  for(int i=0;i<x;++i)
  {
      frame = cvQueryFrame (capture);
      cvShowImage ("Output", frame);
  }
  Release();
  EndQuery();
 }

Upvotes: 2

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