QCamera, QCameraImage Memory Leak ?

mranger90

Hello,
I've been playing with a little toy application to use QCamera and QCameraImage to snap images from the
camera attached to my laptop. I've noticed that even if I do nothing with the images, i.e. just capture on a
timer, there is a noticeable memory leak with each capture. Environment is Ubuntu 12.04/desktop. Video devices
are either the camera attached to the laptop or a Microsoft Lifecam on USB. I've tried tracing the source code,
but it eventually goes down a hole to gstreamer/V4L interface.
The pertinent code is as follows
@
bool StandardCapture::Snap()
{
_m_Camera->searchAndLock();

if(_m_ImageCapture->isReadyForCapture()){
    _m_ImageCapture->capture();
}

_m_Camera->unlock();
return true;

}

void StandardCapture::standardImageCaptured(int id, QImage preview)
{
Q_UNUSED(id)

if(_m_Image) {
    delete _m_Image;
    _m_Image = 0;
}

// copy the image
_m_Image = new QImage(preview);

// then pass the signal up
emit SnapCompleted();

}
@

Note that even if I don't connect the StandardImageCaptured, the leak will still happen.
Other notes are: 1. I am not using an ImagePreview to display the images, I just extract the
buffer in StandardImageCaptured and use that to display. 2. Even though QCameraImage::isReadyForCapture()
returns true, I frequently get output in the debug window saying that the device is not ready.

Thanks

SGaist

Hi,

Just a Qt coding style question: why not take advantage of QImage's implicit sharing ?
It would avoid making several copies of the same image.

mranger90

Hello,
Thanks for replying.

There are 2 reasons why I don't use the sharing. 1. This is just a toy app for me to learn a little bit
about how the interface works and how to manipulate Qimages. I've use the imageviewer and connected everything up and it works nicely, except I didn't really learn anything.
2. I also use this app to connect to a frame grabber board and use its native API to acquire images, hence the capture code displayed is in a "StandardCapture" class as opposed to the (not shown) "MfgCapture" class. So until I figure out how to connect then frame grabber to the image viewer (without using its V4L interface) I wanted to keep the access consistent.

? Offline

I have noticed that the imageCapture->capture(); in the QT camera.pro example also exhibits a memory leak (at least under Linux). I have filed a bug report here:

https://bugreports.qt-project.org/browse/QTBUG-41606

I'm actually working on FabScan100 scanner software, and the memory leak blows the PC away after a couple of hundred frames.