debug wierd constellation results due to bad indexing

sampling.py

@@ -1,4 +1,5 @@
 import numpy as np
+import itertools
 import logging
 
 log = logging.getLogger(__name__)
@@ -32,12 +33,14 @@ class Interpolator(object):
 
 class Sampler(object):
     def __init__(self, src, interp=None):
-        self.src = iter(src)
         self.freq = 1.0
         self.interp = interp if (interp is not None) else Interpolator()
-        coeffs, begin = self.interp.get(0)
-        self.offset = -begin  # should fill samples buffer
-        self.buff = np.zeros(len(coeffs))
+
+        # TODO: explain indices arithmetic
+        padding = [0.0] * (self.interp.width - 1)
+        self.src = itertools.chain(padding, src)
+        self.offset = self.interp.width + 1
+        self.buff = np.zeros(self.interp.coeff_len)
         self.index = 0
 
     def __iter__(self):