1. A method performed by a computer for encoding a signal comprising: defining a 1-D cubic-spline filter by R ⁡ ( t ) = { ( 3 / 2 ) ⁢  t  3 - ( 5 / 2 ) ⁢  t  2 + 1 , 0 ≤  t  < 1 - ( 1 / 2 ) ⁢  t  3 + ( 5 / 2 ) ⁢  t  2 - 4 ⁢  t  + 2 , 1 ≤  t  < 2 ; 0 , 2 ≤  t  ; ( 1 ) applying the filter to an input signal x(t) with y j = ∑ t = - 2 ⁢ ⁢ τ + 1 2 ⁢ ⁢ τ + 1 ⁢ r ⁡ ( t ) ⁢ ⁢ x ⁡ ( t + j ⁢ ⁢ τ ) , 0 ≤ j ≤ n - 1 , ( 3 ) to compute y j ; computing B=[b 0 ,b 1 ,. .. ,b n−1 ] C , where B denotes acyclic matrix of size n×n, where b k = ∑ t = - 2 ⁢ ⁢ τ + 1 2 ⁢ ⁢ τ + 1 ⁢ r ⁡ ( t ) ⁢ ⁢ r ⁡ ( t + k ⁢ ⁢ τ ). 0 ≤ k ≤ n - 1 ( 4 ) and where b 0 =α=1.641, b 1 =b n−1 =0.246, b 2 =b n−2 =γ=−0.07, b 3 =b n−3 =δ=0.004, b 4=0 , b 5=0 ,. .. , b n−4 =0; computing A=B −1 , where A is a circular matrix of size n×n, where 
 A=[a 0 ,a 1 ,a 2 ,a 3 ,a 4 ,a 5 ,a 6 ,. .. ,a n−6 ,a n−5 ,a n−4 ,a n−3 ,a n−2 ,a n−1 ] C (6) and where a 0 =0.646, a 1 =a n−1 =−0.109, a 2 =a n−2 =0.0467, a 3 =a n−3 =−0.014, a 4 =a n−4 =0.0046, a 5 =a n−5 =−0.00148, and a 6 ≅a 7 ≅a 8 ≅. .. ≅a n−6 ≅0; and computing 
 X=B −1 Y=AY (7) by computing x j = ∑ k = 0 n - 1 ⁢ y k ⁢ ⁢ a ( j - k ) n. ( 8 )