FilterBankDesigner now handles sampling frequencies other than 48 kHz; added norm compliance test script. If part of the (1/3 or 1/1) octave band lies above the Nyquist frequency, a high pass filter is returned. If the whole band lies above the Nyquist frequency, a no pass filter is returned.
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@ -186,6 +186,14 @@ class FilterBankDesigner:
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x = self.sanitize_input(x)
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fu_n = fu / fnyq
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# Handle fl & fu >= fNyquist: return 'no pass'
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if fl_n >= 1:
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return np.tile(np.asarray([0, 0, 0, 1, 0, 0]), (SOS_ORDER, 1))
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# Handle fu >= fNyquist: return high pass
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if fu_n >= 1:
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return butter(SOS_ORDER, fl_n, output='sos', btype='highpass')
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return butter(SOS_ORDER, [fl_n, fu_n], output='sos', btype='band')
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def firFreqResponse(self, x, freq):
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@ -450,8 +458,9 @@ class OctaveBankDesigner(FilterBankDesigner):
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if int(self.fs) in [44100, 48000, 96000]:
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return 1.0
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else:
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raise ValueError('Unimplemented sampling frequency \'{} Hz\' for '
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'SOS filter design. Try 48 kHz.'.format(self.fs))
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warnings.warn(f'Sampling frequency {self.fs} Hz might result in '
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'incorrect filters. Use 48 kHz instead.')
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return 1.0
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def sosFac_u(self, x):
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"""Right side percentage of change in cut-on frequency for designing
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@ -463,8 +472,9 @@ class OctaveBankDesigner(FilterBankDesigner):
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if int(self.fs) in [44100, 48000, 96000]:
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return 1.0
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else:
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raise ValueError('Unimplemented sampling frequency \'{} Hz\' for '
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'SOS filter design. Try 48 kHz.'.format(self.fs))
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warnings.warn(f'Sampling frequency {self.fs} Hz might result in '
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'incorrect filters. Use 48 kHz instead.')
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return 1.0
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class ThirdOctaveBankDesigner(FilterBankDesigner):
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@ -475,8 +485,7 @@ class ThirdOctaveBankDesigner(FilterBankDesigner):
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one-third octave bands
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Args:
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fs: Sampling frequency in [Hz]
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fs: Sampling frequency in [Hz] - can be None
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"""
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super().__init__(fs)
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self.xs = list(range(-16, 14))
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@ -485,8 +494,7 @@ class ThirdOctaveBankDesigner(FilterBankDesigner):
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'25', '31.5', '40', '50', '63', '80', '100', '125', '160', '200',
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'250', '315', '400', '500', '630', '800', '1k', '1.25k', '1.6k',
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'2k', '2.5k', '3.15k', '4k', '5k', '6.3k', '8k', '10k', '12.5k',
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'16k', '20k'
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]
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'16k', '20k']
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assert len(self.xs) == len(self._nominal_txt)
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@ -603,25 +611,19 @@ class ThirdOctaveBankDesigner(FilterBankDesigner):
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"""Left side percentage of change in cut-on frequency for designing the
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filter."""
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# Idea: correct for frequency warping:
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if np.isclose(self.fs, 48000):
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return 1.00
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elif np.isclose(self.fs, 44100):
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warnings.warn(f'Sampling frequency {self.fs} Hz might result in '
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'incorrect filters')
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return 1.00
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elif np.isclose(self.fs, 32768):
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return 1.00
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if int(self.fs) in [48000]:
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return 1.0
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else:
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raise ValueError('Unimplemented sampling frequency \'{} Hz\' for '
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'SOS filter design. Try 48 kHz.'.format(self.fs))
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warnings.warn(f'Sampling frequency {self.fs} Hz might result in '
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'incorrect filters. Use 48 kHz instead.')
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return 1.0
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def sosFac_u(self, x):
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"""Right side percentage of change in cut-on frequency for designing
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the filter."""
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if np.isclose(self.fs, 48000):
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return 1
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elif np.isclose(self.fs, 32768):
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return 1.00
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if int(self.fs) in [48000]:
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return 1.0
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else:
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raise ValueError('Unimplemented sampling frequency \'{} Hz\' for '
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'SOS filter design. Try 48 kHz.'.format(self.fs))
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warnings.warn(f'Sampling frequency {self.fs} Hz might result in '
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'incorrect filters. Use 48 kHz instead.')
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return 1.0
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@ -0,0 +1,63 @@
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"""
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This script checks whether the 3rd octave equalizer is norm compliant.
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Created on Tue Dec 31 14:43:19 2019
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@author: anne
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"""
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from lasp.filter import (ThirdOctaveBankDesigner)
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import matplotlib.pyplot as plt
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import numpy as np
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from scipy.signal import freqz, iirdesign, sosfreqz, butter, cheby2
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plt.close('all')
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# %% Settings of 'filter under test'
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fs = 44.1e3
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nsections = 5 # filter property
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designer = ThirdOctaveBankDesigner(fs)
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xmin = designer.nominal_txt_tox('25') # lowest highest band, nominal name
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xmax = designer.nominal_txt_tox('20k') # highest band
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# %% Run check
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compliant = True # remains True if all filters comply
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fnyq = fs/2
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fll = designer.fl(xmin) / 1.1 # plot limits
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fuu = designer.fu(xmax) * 1.1
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fig = plt.figure()
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plt.xlabel('f (Hz)')
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plt.ylabel('Magnitude (dB)')
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for x in range(xmin, xmax+1): # loop over bands
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fl = designer.fl(x) # lower cut off
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fu = designer.fu(x) # upper
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fln = fl/fnyq # lower cutoff, normalized [0, 1]
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fun = fu/fnyq # upper
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print(designer.nominal_txt(x))
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sos = designer.createSOSFilter(x)
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fnorm, h = sosfreqz(sos, worN=2**18, whole=False)
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freq = fnorm*fnyq/np.pi
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h_dB = 20*np.log10(np.abs(h) + np.finfo(float).eps)
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if not designer.testStandardCompliance(x, freq, h_dB):
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print('==============================')
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print(designer.nominal_txt(x), ' does not comply')
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compliant = False
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plt.semilogx(freq, h_dB)
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# Upper / lower limits
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freqlim, ulim, llim = designer.band_limits(x)
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plt.semilogx(freqlim, ulim)
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plt.semilogx(freqlim, llim)
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plt.ylim(-5, 1)
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plt.xlim(fll, fuu)
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print(f"\nPassed test : {compliant}")
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