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This is of course an opencv's noob question but I need to clarify something about BackgroundSubtractorMOG2 and how to use it.

I am looking more in depth the source code for BackgroundSubtractorMOG2 class, particularly the apply method:

void BackgroundSubtractorMOG2Impl::apply(InputArray _image, OutputArray _fgmask, double learningRate)
{
    CV_INSTRUMENT_REGION()

    bool needToInitialize = nframes == 0 || learningRate >= 1 || _image.size() != frameSize || _image.type() != frameType;

    if( needToInitialize )
        initialize(_image.size(), _image.type());

#ifdef HAVE_OPENCL
    if (opencl_ON)
    {
        CV_OCL_RUN(_image.isUMat(), ocl_apply(_image, _fgmask, learningRate))

        opencl_ON = false;
        initialize(_image.size(), _image.type());
    }
#endif

    Mat image = _image.getMat();
    _fgmask.create( image.size(), CV_8U );
    Mat fgmask = _fgmask.getMat();

    ++nframes;
    learningRate = learningRate >= 0 && nframes > 1 ? learningRate : 1./std::min( 2*nframes, history );
    CV_Assert(learningRate >= 0);

    parallel_for_(Range(0, image.rows),
                  MOG2Invoker(image, fgmask,
                              bgmodel.ptr<GMM>(),
                              (float*)(bgmodel.ptr() + sizeof(GMM)*nmixtures*image.rows*image.cols),
                              bgmodelUsedModes.ptr(), nmixtures, (float)learningRate,
                              (float)varThreshold,

                              backgroundRatio, varThresholdGen,
                              fVarInit, fVarMin, fVarMax, float(-learningRate*fCT), fTau,
                              bShadowDetection, nShadowDetection),
                              image.total()/(double)(1 << 16));
}

which is the method to call when we want to generate the foreground.

When using it in a loop, it is correct that I should check for the foreground creation every nframes times I calls the apply method ?

This is of course an opencv's noob question but I need to clarify something about BackgroundSubtractorMOG2 and how to use it.

I am looking more in depth the source code for BackgroundSubtractorMOG2 class, particularly the apply method:

void BackgroundSubtractorMOG2Impl::apply(InputArray _image, OutputArray _fgmask, double learningRate)
{
    CV_INSTRUMENT_REGION()

    bool needToInitialize = nframes == 0 || learningRate >= 1 || _image.size() != frameSize || _image.type() != frameType;

    if( needToInitialize )
        initialize(_image.size(), _image.type());

#ifdef HAVE_OPENCL
    if (opencl_ON)
    {
        CV_OCL_RUN(_image.isUMat(), ocl_apply(_image, _fgmask, learningRate))

        opencl_ON = false;
        initialize(_image.size(), _image.type());
    }
#endif

    Mat image = _image.getMat();
    _fgmask.create( image.size(), CV_8U );
    Mat fgmask = _fgmask.getMat();

    ++nframes;
    learningRate = learningRate >= 0 && nframes > 1 ? learningRate : 1./std::min( 2*nframes, history );
    CV_Assert(learningRate >= 0);

    parallel_for_(Range(0, image.rows),
                  MOG2Invoker(image, fgmask,
                              bgmodel.ptr<GMM>(),
                              (float*)(bgmodel.ptr() + sizeof(GMM)*nmixtures*image.rows*image.cols),
                              bgmodelUsedModes.ptr(), nmixtures, (float)learningRate,
                              (float)varThreshold,

                              backgroundRatio, varThresholdGen,
                              fVarInit, fVarMin, fVarMax, float(-learningRate*fCT), fTau,
                              bShadowDetection, nShadowDetection),
                              image.total()/(double)(1 << 16));
}

which is the method to call when we want to generate the foreground.

When using it in a infinite loop, it is correct that I should check for the new foreground creation every nframes times I calls the apply method ?