It turns out sorting exit data does not need to happen.
Issues of non-static speckle pattern (without US modulation)
have disappeared with corrections in last commit.

Also, if looking at delta speckle contrast in post-processing
the number of pixels in the CCD is important (the larger the better),
since it is a statistical approach.  Should look into another
way to process data (power spectral density?) since the more pixels
the larger the processing time.