As mentioned in the newsgroup it will depend on what you are trying to accomplish. For example, here is the image with the contrast improved a bit
and then averaged (mean) filtered
and then thresholded to a white mask
whose blobs are then replaced with equivalent circles to yield
Note that these filters are very fast and should get about 20fps on a reasonable machine. You can try the filter below by clicking on the download (note you need Roborealm installed before clicking)
Is there a particular quality that you are looking for in the clustering?