Added safety checks for filter stability

Author: anscian

audio_filters/butterworth_filter.py

@@ -9,7 +9,22 @@
 Alternatively you can use scipy.signal.butter, which should yield the same results.
 """
 
-
+# All calls to filter creators must have keyword arguments
+def safe_checks(filter_creator):
+    def safe_filter_creator(**kwargs):
+        if not isinstance(kwargs['frequency'], int) or kwargs['frequency'] <= 0:
+            raise ValueError('Frequency must be a positive integer.')
+        if not isinstance(kwargs['samplerate'], int) or kwargs['samplerate'] <= 0:
+            raise ValueError('Samplerate must be a positive integer.')
+        if not (0 < kwargs['frequency'] < kwargs['samplerate'] / 2):
+            raise ValueError('Frequency must be less than half of the samplerate.')
+        if kwargs['q_factor'] <= 0:
+            raise ValueError('Q factor must be positive.')
+        return filter_creator(**kwargs)
+    return safe_filter_creator
+
+
+@safe_checks
 def make_lowpass(
     frequency: int,
     samplerate: int,
@@ -40,6 +55,7 @@ def make_lowpass(
     return filt
 
 
+@safe_checks
 def make_highpass(
     frequency: int,
     samplerate: int,
@@ -70,6 +86,7 @@ def make_highpass(
     return filt
 
 
+@safe_checks
 def make_bandpass(
     frequency: int,
     samplerate: int,
@@ -101,6 +118,7 @@ def make_bandpass(
     return filt
 
 
+@safe_checks
 def make_allpass(
     frequency: int,
     samplerate: int,
@@ -128,6 +146,7 @@ def make_allpass(
     return filt
 
 
+@safe_checks
 def make_peak(
     frequency: int,
     samplerate: int,
@@ -160,6 +179,7 @@ def make_peak(
     return filt
 
 
+@safe_checks
 def make_lowshelf(
     frequency: int,
     samplerate: int,
@@ -197,6 +217,7 @@ def make_lowshelf(
     return filt
 
 
+@safe_checks
 def make_highshelf(
     frequency: int,
     samplerate: int,