Upsampling - Approximated Sinc Interpolation in Python

approx_sinc_interp.py

# Written by Nadav Benedek
import numpy as np
from numba import jit, autojit
import scipy

@jit(nopython=True)
def approx_sinc_interp(x, s, u):
    MAX_ELEMENTS_TO_TAKE_EACH_SIDE = 20  # Change this number to change the accuracy
    result = np.empty(len(u)) 
    
    T = float(s[1] - s[0])  # Find the period    
    
    for i in xrange(0, len(u)):
        t = float(i) * T * len(x) / float(len(u))        
        sum = 0.0
        for n in xrange(np.maximum(int(-MAX_ELEMENTS_TO_TAKE_EACH_SIDE + t/T), 0), np.minimum(int(MAX_ELEMENTS_TO_TAKE_EACH_SIDE + t/T), len(x))):             
             sum = sum + x[n]*np.sinc((t- float(n)*T)/T)
        result[i] = sum
    
    return result