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# coding: utf-8
"""
=======
Presets
=======
This notebook demonstrates how to use the `presets` package to change the
default parameters for librosa.
"""
# Code source: Brian McFee
# License: ISC
##################################################
# We'll need numpy and matplotlib for this example
import numpy as np
import matplotlib.pyplot as plt
# Import the Preset class
from presets import Preset
# To use presets, we'll make a mock import of librosa
import librosa as _librosa
#########################################################################
# By default, librosa uses the following parameters across all functions:
# - `sr=22050` (sampling rate)
# - `hop_length=512` (number of samples between frames)
# - `n_fft=2048` (number of samples per frame in STFT-like analyses)
#
# You may want to change these values to suit your application, but
# doing so consistently in every function call can be somewhat cumbersome.
#
# Presets makes it easy to do this all at once by wrapping the module
# and all function calls, and overriding default arguments.
# First, we need to set up the preset-wrapped librosa import
librosa = Preset(_librosa)
# To change the default sampling rate, we can set the `sr` entry:
librosa['sr'] = 44100
# and similarly for hop_length and n_fft
librosa['hop_length'] = 1024
librosa['n_fft'] = 4096
# In general, when you set `librosa['X']` for any string `X`, anywhere within
# librosa where the parameter `X` occurs as a keyword-argument,
# its default value will be replaced by whatever value you provide.
######################################################################
# Now we can load in a file and do some analysis with the new defaults
filename = librosa.ex('fishin')
y, sr = librosa.load(filename, duration=5, offset=35)
# Generate a Mel spectrogram:
M = librosa.feature.melspectrogram(y=y)
# Of course, you can still override the new default manually, e.g.:
M_highres = librosa.feature.melspectrogram(y=y, hop_length=512)
# And plot the results
fig, ax = plt.subplots(nrows=3, sharex=True, sharey=True)
librosa.display.specshow(librosa.power_to_db(M, ref=np.max),
y_axis='mel', x_axis='time', ax=ax[0])
ax[0].set(title='44100/1024/4096')
ax[0].label_outer()
librosa.display.specshow(librosa.power_to_db(M_highres, ref=np.max),
hop_length=512,
y_axis='mel', x_axis='time', ax=ax[1])
ax[1].set(title='44100/512/4096')
ax[1].label_outer()
# We can repeat the whole process with different defaults, just by
# updating the parameter entries
librosa['sr'] = 11025
y2, sr2 = librosa.load(filename, duration=5, offset=35)
M2 = librosa.feature.melspectrogram(y=y2, sr=sr2)
librosa.display.specshow(librosa.power_to_db(M2, ref=np.max),
y_axis='mel', x_axis='time', ax=ax[2])
ax[2].set(title='11025/1024/4096')
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