# Revision history [back]

Thank you for your answer I will try to discover if it is used for the Sobel operator. It,s defined in this function in objectdetect.cpp

CV_WRAP HOGDescriptor() : winSize(64,128), blockSize(16,16), blockStride(8,8), cellSize(8,8), nbins(9), derivAperture(1), winSigma(-1), histogramNormType(HOGDescriptor::L2Hys), L2HysThreshold(0.2), gammaCorrection(true), nlevels(HOGDescriptor::DEFAULT_NLEVELS)

Thank you for your answer I will try to discover if it is used for the Sobel operator. It,s defined in this function in objectdetect.cpp

CV_WRAP HOGDescriptor() : winSize(64,128), blockSize(16,16), blockStride(8,8), cellSize(8,8), nbins(9), derivAperture(1), winSigma(-1), histogramNormType(HOGDescriptor::L2Hys), L2HysThreshold(0.2), gammaCorrection(true), nlevels(HOGDescriptor::DEFAULT_NLEVELS)

If anyone had the same problem I think I have found the solution in: http://www.seas.upenn.edu/~bensapp/opencvdocs/ref/opencvref_cv.htm

aperture_size Size of the extended Sobel kernel, must be 1, 3, 5 or 7. In all cases except 1, aperture_size ×aperture_size separable kernel will be used to calculate the derivative. For aperture_size=1 3x1 or 1x3 kernel is used (Gaussian smoothing is not done).

But I'm not totally sure.