Video filtering with Fermat number theoretic transforms using residue number system

  • Authors:
  • T. Toivonen;J. Heikkila

  • Affiliations:
  • Machine Vision Group, Univ. of Oulu, Finland;-

  • Venue:
  • IEEE Transactions on Circuits and Systems for Video Technology
  • Year:
  • 2006

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Abstract

We investigate image and video convolutions based on Fermat number transform (FNT) modulo q=2M+1 where M is an integer power of two. These transforms are found to be ideal for image convolutions, except that the choices for the word length, restricted by the transform modulus, are rather limited. We discuss two methods to overcome this limitation. First, we allow M to be an arbitrary integer. This gives much wider variety in possible moduli, at the cost of decreased transform length of 16 or 32 points for M1=216+1 and q2=28+1, which allow transforms up to 256 points with a dynamic range of about 24 bits. We design an efficient reconstruction circuit based on mixed radix conversion for converting the result from diminished-1 RNS into normal binary code. The circuit is implemented in VHDL and found to be very small in area. We also discuss the necessary steps in performing convolutions with the GFNT and evaluate the integrated circuit implementation cost for various elementary operations.