As stated in the title, SIFT Feature Descriptor doesn't work with ORB keypoints, I changed the useProvidedKeypoints to true but it still doesn't work and I get the "Vector subscript out of range" error in the extractor.compute line. Part of the code is below.
ORB detector(500);
detector.detect( img1, keypointsB );
SiftDescriptorExtractor extractor;
extractor.compute( img1, keypointsB, descriptorsB);