OpenCV SURF, is it normal that the captured videos lag by a little? How to speed it up?

Question

How do I speed up the correspondence matching processes of SURF? I used the samples provided and changed it to capture color images from the webcam for processing, however, the speed certainly needs improvement. Where should this be tackled on?

Answer 1

First, SURF (at least, OpenCV's one) supports only gray images.

There are lots of descriptors parameters avalable to tune, setting them to lower values can increase performance:

typedef struct CvSURFParams
{
   int extended; // 0 means basic descriptors (64 elements each),
                 // 1 means extended descriptors (128 elements each)
   double hessianThreshold; // only features with keypoint.hessian
         // larger than that are extracted.
                 // good default value is ~300-500 (can depend on the
         // average local contrast and sharpness of the image).
                 // user can further filter out some features based on
         // their hessian values and other characteristics.
   int nOctaves; // the number of octaves to be used for extraction.
                 // With each next octave the feature size is doubled
         // (3 by default)
   int nOctaveLayers; // The number of layers within each octave
         // (4 by default)
}
CvSURFParams;

See OpenCV's SURF docs.

Also, check out original article and notes on OpenSURF lib