"""
This module provides scipy versions of high_pass_filter, and low_pass_filter
as well as an additional band_pass_filter.
Of course, you will need to install scipy for these to work.
When this module is imported the high and low pass filters from this module
will be used when calling audio_segment.high_pass_filter() and
audio_segment.high_pass_filter() instead of the slower, less powerful versions
provided by pydub.effects.
"""
from scipy.signal import butter, sosfilt
from .utils import (register_pydub_effect,stereo_to_ms,ms_to_stereo)
def _mk_butter_filter(freq, type, order):
"""
Args:
freq: The cutoff frequency for highpass and lowpass filters. For
band filters, a list of [low_cutoff, high_cutoff]
type: "lowpass", "highpass", or "band"
order: nth order butterworth filter (default: 5th order). The
attenuation is -6dB/octave beyond the cutoff frequency (for 1st
order). A Higher order filter will have more attenuation, each level
adding an additional -6dB (so a 3rd order butterworth filter would
be -18dB/octave).
Returns:
function which can filter a mono audio segment
"""
def filter_fn(seg):
assert seg.channels == 1
nyq = 0.5 * seg.frame_rate
try:
freqs = [f / nyq for f in freq]
except TypeError:
freqs = freq / nyq
sos = butter(order, freqs, btype=type, output='sos')
y = sosfilt(sos, seg.get_array_of_samples())
return seg._spawn(y.astype(seg.array_type))
return filter_fn
@register_pydub_effect
def band_pass_filter(seg, low_cutoff_freq, high_cutoff_freq, order=5):
filter_fn = _mk_butter_filter([low_cutoff_freq, high_cutoff_freq], 'band', order=order)
return seg.apply_mono_filter_to_each_channel(filter_fn)
@register_pydub_effect
def high_pass_filter(seg, cutoff_freq, order=5):
filter_fn = _mk_butter_filter(cutoff_freq, 'highpass', order=order)
return seg.apply_mono_filter_to_each_channel(filter_fn)
@register_pydub_effect
def low_pass_filter(seg, cutoff_freq, order=5):
filter_fn = _mk_butter_filter(cutoff_freq, 'lowpass', order=order)
return seg.apply_mono_filter_to_each_channel(filter_fn)
@register_pydub_effect
def _eq(seg, focus_freq, bandwidth=100, mode="peak", gain_dB=0, order=2):
"""
Args:
focus_freq - middle frequency or known frequency of band (in Hz)
bandwidth - range of the equalizer band
mode - Mode of Equalization(Peak/Notch(Bell Curve),High Shelf, Low Shelf)
order - Rolloff factor(1 - 6dB/Octave 2 - 12dB/Octave)
Returns:
Equalized/Filtered AudioSegment
"""
filt_mode = ["peak", "low_shelf", "high_shelf"]
if mode not in filt_mode:
raise ValueError("Incorrect Mode Selection")
if gain_dB >= 0:
if mode == "peak":
sec = band_pass_filter(seg, focus_freq - bandwidth/2, focus_freq + bandwidth/2, order = order)
seg = seg.overlay(sec - (3 - gain_dB))
return seg
if mode == "low_shelf":
sec = low_pass_filter(seg, focus_freq, order=order)
seg = seg.overlay(sec - (3 - gain_dB))
return seg
if mode == "high_shelf":
sec = high_pass_filter(seg, focus_freq, order=order)
seg = seg.overlay(sec - (3 - gain_dB))
return seg
if gain_dB < 0:
if mode == "peak":
sec = high_pass_filter(seg, focus_freq - bandwidth/2, order=order)
seg = seg.overlay(sec - (3 + gain_dB)) + gain_dB
sec = low_pass_filter(seg, focus_freq + bandwidth/2, order=order)
seg = seg.overlay(sec - (3 + gain_dB)) + gain_dB
return seg
if mode == "low_shelf":
sec = high_pass_filter(seg, focus_freq, order=order)
seg = seg.overlay(sec - (3 + gain_dB)) + gain_dB
return seg
if mode=="high_shelf":
sec=low_pass_filter(seg, focus_freq, order=order)
seg=seg.overlay(sec - (3 + gain_dB)) +gain_dB
return seg
@register_pydub_effect
def eq(seg, focus_freq, bandwidth=100, channel_mode="L+R", filter_mode="peak", gain_dB=0, order=2):
"""
Args:
focus_freq - middle frequency or known frequency of band (in Hz)
bandwidth - range of the equalizer band
channel_mode - Select Channels to be affected by the filter.
L+R - Standard Stereo Filter
L - Only Left Channel is Filtered
R - Only Right Channel is Filtered
M+S - Blumlien Stereo Filter(Mid-Side)
M - Only Mid Channel is Filtered
S - Only Side Channel is Filtered
Mono Audio Segments are completely filtered.
filter_mode - Mode of Equalization(Peak/Notch(Bell Curve),High Shelf, Low Shelf)
order - Rolloff factor(1 - 6dB/Octave 2 - 12dB/Octave)
Returns:
Equalized/Filtered AudioSegment
"""
channel_modes = ["L+R", "M+S", "L", "R", "M", "S"]
if channel_mode not in channel_modes:
raise ValueError("Incorrect Channel Mode Selection")
if seg.channels == 1:
return _eq(seg, focus_freq, bandwidth, filter_mode, gain_dB, order)
if channel_mode == "L+R":
return _eq(seg, focus_freq, bandwidth, filter_mode, gain_dB, order)
if channel_mode == "L":
seg = seg.split_to_mono()
seg = [_eq(seg[0], focus_freq, bandwidth, filter_mode, gain_dB, order), seg[1]]
return AudioSegment.from_mono_audio_segements(seg[0], seg[1])
if channel_mode == "R":
seg = seg.split_to_mono()
seg = [seg[0], _eq(seg[1], focus_freq, bandwidth, filter_mode, gain_dB, order)]
return AudioSegment.from_mono_audio_segements(seg[0], seg[1])
if channel_mode == "M+S":
seg = stereo_to_ms(seg)
seg = _eq(seg, focus_freq, bandwidth, filter_mode, gain_dB, order)
return ms_to_stereo(seg)
if channel_mode == "M":
seg = stereo_to_ms(seg).split_to_mono()
seg = [_eq(seg[0], focus_freq, bandwidth, filter_mode, gain_dB, order), seg[1]]
seg = AudioSegment.from_mono_audio_segements(seg[0], seg[1])
return ms_to_stereo(seg)
if channel_mode == "S":
seg = stereo_to_ms(seg).split_to_mono()
seg = [seg[0], _eq(seg[1], focus_freq, bandwidth, filter_mode, gain_dB, order)]
seg = AudioSegment.from_mono_audio_segements(seg[0], seg[1])
return ms_to_stereo(seg)
