Help me to understand ORB parameters [closed]

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Hi,

I use ORB for a project and I need to understand how it works.

I don't understand all the parameters of ORB constructor, can you help me ?

I need to optimise time of research / precision

Parameters :

1. nfeatures : number of keypoints,more keypoint increase time of research
2. scaleFactor : lower (close to 1.0f) increase precision and increase time
3. nlevels : number of level of pyramids. Don't understand how that affect time or precision
4. edgeThreshold size of the keypoint ? Don't understand how that affect time or precision
5. patchSize need to match edge ???

Thanks.