cv::calibrateCamera fails to start optimization at all with some input images (Bug #592)

The problem occurs in cvLevMarqu.updateALT at the line containing change = cvNorm(param, prevParam, CV_RELATIVE_L2)) < criteria.epsilon

For some reason (I could not find out in 8hrs debugging), param and prevParam are sometimes identical, causing the iteration to stop prematurely. In one case with 21 chessboard input images (enclosed), it even stopped without any iteration at all. Removing an arbitrary one of the images let the iteration start. However, testing a lot of calibration sequences showed that every now and then iterations stop prematurely because of param prevparam.

I made a log of the input parameters to the attached file, however did not test, whether it would be possible to reproduce the case by reading them and calling calibrateCamera in a small test case. Flag settings are not recorded in the file. They are CV_CALIB_FIX_ASPECT_RATIO + CV_CALIB_FIX_K3 + CV_CALIB_ZERO_TANGENT_DIST.

I have made a workaround by adding &&(change != 0) to the expression in a local copy of cvcalibration.exe. But since I do not understand how the paramprevparam condition occurs this may not cure the underlying problem.