Description of StereoBM PREFILTER_NORMALIZED_RESPONSE

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Can someone point me to a description of StereoBM's "Normalized Response" prefilter?

StereoBM has two prefilter options: Sobel and Normalized Response. The Sobel operator is well known and easy to find information for, but I can't find any high-level information about a normalized response filter outside of OpenCV's docs. Does it go by some other name elsewhere?

Best regards.