Fix: updated filter code

Author: ShubhamRaghu03

audio_filters/butterworth_filter.py

@@ -1,5 +1,4 @@
 from math import cos, sin, sqrt, tau
-
 from audio_filters.iir_filter import IIRFilter
 
 """
@@ -9,28 +8,21 @@
 Alternatively you can use scipy.signal.butter, which should yield the same results.
 """
 
-
-def make_lowpass(
-    frequency: int,
-    samplerate: int,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates a low-pass filter
-
-    >>> filter = make_lowpass(1000, 48000)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.004277569313094809,
-     0.008555138626189618, 0.004277569313094809]
-    """
+def _precompute(frequency: int, samplerate: int, q_factor: float):
+    """Helper to compute common values for filter design."""
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
     _cos = cos(w0)
     alpha = _sin / (2 * q_factor)
+    return _sin, _cos, alpha
+
+
+def make_lowpass(frequency: int, samplerate: int, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates a low-pass filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
 
     b0 = (1 - _cos) / 2
     b1 = 1 - _cos
-
     a0 = 1 + alpha
     a1 = -2 * _cos
     a2 = 1 - alpha
@@ -40,27 +32,12 @@ def make_lowpass(
     return filt
 
 
-def make_highpass(
-    frequency: int,
-    samplerate: int,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates a high-pass filter
-
-    >>> filter = make_highpass(1000, 48000)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.9957224306869052,
-     -1.9914448613738105, 0.9957224306869052]
-    """
-    w0 = tau * frequency / samplerate
-    _sin = sin(w0)
-    _cos = cos(w0)
-    alpha = _sin / (2 * q_factor)
+def make_highpass(frequency: int, samplerate: int, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates a high-pass filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
 
     b0 = (1 + _cos) / 2
     b1 = -1 - _cos
-
     a0 = 1 + alpha
     a1 = -2 * _cos
     a2 = 1 - alpha
@@ -70,28 +47,13 @@ def make_highpass(
     return filt
 
 
-def make_bandpass(
-    frequency: int,
-    samplerate: int,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates a band-pass filter
-
-    >>> filter = make_bandpass(1000, 48000)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.06526309611002579,
-     0, -0.06526309611002579]
-    """
-    w0 = tau * frequency / samplerate
-    _sin = sin(w0)
-    _cos = cos(w0)
-    alpha = _sin / (2 * q_factor)
+def make_bandpass(frequency: int, samplerate: int, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates a band-pass filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
 
     b0 = _sin / 2
     b1 = 0
     b2 = -b0
-
     a0 = 1 + alpha
     a1 = -2 * _cos
     a2 = 1 - alpha
@@ -101,23 +63,9 @@ def make_bandpass(
     return filt
 
 
-def make_allpass(
-    frequency: int,
-    samplerate: int,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates an all-pass filter
-
-    >>> filter = make_allpass(1000, 48000)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.9077040443587427,
-     -1.9828897227476208, 1.0922959556412573]
-    """
-    w0 = tau * frequency / samplerate
-    _sin = sin(w0)
-    _cos = cos(w0)
-    alpha = _sin / (2 * q_factor)
+def make_allpass(frequency: int, samplerate: int, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates an all-pass filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
 
     b0 = 1 - alpha
     b1 = -2 * _cos
@@ -128,24 +76,9 @@ def make_allpass(
     return filt
 
 
-def make_peak(
-    frequency: int,
-    samplerate: int,
-    gain_db: float,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates a peak filter
-
-    >>> filter = make_peak(1000, 48000, 6)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0653405327119334, -1.9828897227476208, 0.9346594672880666, 1.1303715025601122,
-     -1.9828897227476208, 0.8696284974398878]
-    """
-    w0 = tau * frequency / samplerate
-    _sin = sin(w0)
-    _cos = cos(w0)
-    alpha = _sin / (2 * q_factor)
+def make_peak(frequency: int, samplerate: int, gain_db: float, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates a peak filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
     big_a = 10 ** (gain_db / 40)
 
     b0 = 1 + alpha * big_a
@@ -160,25 +93,11 @@ def make_peak(
     return filt
 
 
-def make_lowshelf(
-    frequency: int,
-    samplerate: int,
-    gain_db: float,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates a low-shelf filter
-
-    >>> filter = make_lowshelf(1000, 48000, 6)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [3.0409336710888786, -5.608870992220748, 2.602157875636628, 3.139954022810743,
-     -5.591841778072785, 2.5201667380627257]
-    """
-    w0 = tau * frequency / samplerate
-    _sin = sin(w0)
-    _cos = cos(w0)
-    alpha = _sin / (2 * q_factor)
+def make_lowshelf(frequency: int, samplerate: int, gain_db: float, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates a low-shelf filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
     big_a = 10 ** (gain_db / 40)
+
     pmc = (big_a + 1) - (big_a - 1) * _cos
     ppmc = (big_a + 1) + (big_a - 1) * _cos
     mpc = (big_a - 1) - (big_a + 1) * _cos
@@ -197,25 +116,11 @@ def make_lowshelf(
     return filt
 
 
-def make_highshelf(
-    frequency: int,
-    samplerate: int,
-    gain_db: float,
-    q_factor: float = 1 / sqrt(2),
-) -> IIRFilter:
-    """
-    Creates a high-shelf filter
-
-    >>> filter = make_highshelf(1000, 48000, 6)
-    >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [2.2229172136088806, -3.9587208137297303, 1.7841414181566304, 4.295432981120543,
-     -7.922740859457287, 3.6756456963725253]
-    """
-    w0 = tau * frequency / samplerate
-    _sin = sin(w0)
-    _cos = cos(w0)
-    alpha = _sin / (2 * q_factor)
+def make_highshelf(frequency: int, samplerate: int, gain_db: float, q_factor: float = 1 / sqrt(2)) -> IIRFilter:
+    """Creates a high-shelf filter."""
+    _sin, _cos, alpha = _precompute(frequency, samplerate, q_factor)
     big_a = 10 ** (gain_db / 40)
+
     pmc = (big_a + 1) - (big_a - 1) * _cos
     ppmc = (big_a + 1) + (big_a - 1) * _cos
     mpc = (big_a - 1) - (big_a + 1) * _cos