Method and device for high speed scale conversion

A method of scale conversion to obtain a first value M within a first range defined by a lower limit M1 and an upper limit M2 from a second value N within a second range defined by a lower limit N1 and an upper limit N2, wherein the second range is greater than the first range, wherein a multi-bit shift register is used to carry out approximating division, said method comprising the steps of:

• 1) determining a positive integer p such that
• |q−2p|<|q−2p−1|
• and
• |q−2p|≦|q−2p+1|,
• wherein q=(N2−N1)/(M2−M1);
• 2) obtaining an integer D such that
• D=R{(N2−N1)*|(1/q−1/2p−1)|}
• wherein R{x} is a rounded off value of x;
• 3) storing a series of correction values C(n) for n=0 to n=D such that
• C(n)=R{(2n−1)*Q}
• wherein Q=(N2−N1)/2D;
• 4) dividing a value V(N)=(N−N1+2p−1) by 2p to obtain a reduced value A(N);
• 5) using a binary search process to compare (N−N1) to the stored values of C(n) in order to obtain an integer m such that
• C(m)≦(N−N1)<C(m+1)
• 6) assigning an error value E(N) to be equal to m obtained in step 5;
• and
• 7) obtaining the value M from
• M=A(N)+M1+E(N).

A device for converting a first digital signal indicative of a value N within a first range defined by a lower limit N1 and an upper limit N2 into a second digital signal indicative of a value M within a second range defined by a lower limit M1 and an upper limit M2, comprising:

• means (30) for storing the first signal;
• means (40), responsive to the first signal, for obtaining a positive integer p from the first range and the second range, wherein the integer p is defined by
• |q−2p|<|q 2p−1
• and
• |q−2p|≦|q−2p+1,
• and
• q=(N2−N1)/(M2−M2);
• means (50), responsive to the integer p, for obtaining an error value E(N) in a binary search process;
• and
• means (60), responsive to the integer p and the error value E(N), for obtaining a reduced value A(N) for providing the second signal.