Add scipy-powered filters and bump version

pydub/effects.py

@@ -16,6 +16,21 @@
     xrange = range
 
 
+@register_pydub_effect
+def apply_mono_filter_to_each_channel(seg, filter_fn):
+    n_channels = seg.channels
+
+    channel_segs = seg.split_to_mono()
+    channel_segs = [filter_fn(channel_seg) for channel_seg in channel_segs]
+
+    out_data = seg.get_array_of_samples()
+    for channel_i, channel_seg in enumerate(channel_segs):
+        for sample_i, sample in enumerate(channel_seg.get_array_of_samples()):
+            index = (sample_i * n_channels) + channel_i
+            out_data[index] = sample
+
+    return seg._spawn(out_data.tostring())
+
 
 @register_pydub_effect
 def normalize(seg, headroom=0.1):
@@ -303,4 +318,4 @@ def apply_gain_stereo(seg, left_gain=0.0, right_gain=0.0):
 
     return seg._spawn(data=output,
                 overrides={'channels': 2,
-                           'frame_width': 2 * seg.sample_width})
+                           'frame_width': 2 * seg.sample_width})

pydub/scipy_effects.py

@@ -0,0 +1,60 @@
+"""
+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 are 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
+
+
+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)
+
+    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).tostring())
+
+    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)

setup.py

@@ -8,7 +8,7 @@
 
 setup(
     name='pydub',
-    version='0.16.5',
+    version='0.16.6',
     author='James Robert',
     author_email='jiaaro@gmail.com',
     description='Manipulate audio with an simple and easy high level interface',