Some utility functions for audio processing

audio.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
BSD 3-Clause License

Copyright (c) 2017, Michal Szczepanski
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

* Neither the name of the copyright holder nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
import sys
import scipy.io.wavfile as wav
import numpy as np
import matplotlib.pyplot as plt

""" PROCESS DATA """


def to_mono(fname, channel=0):
    """
    Opens wav file and returns it as mono file if stereo
    :param fname: file name
    :param channel: channel index - default 0
    :return: tuple of frequency and data numpy array
    """
    (freq, sig) = wav.read(fname)
    if sig.ndim == 2:
        return (sig[:,channel], freq)
    return (sig, freq)


def cut(data, freq, start, end):
    """
    Cut track array from start (in seconds) to end (in seconds)
    or till end of track if end second is bigger then track length
    :param track: wav audio data
    :param start: start (in seconds)
    :param end: end (in seconds)
    :param freq: frequency of audio data
    :return:
    """
    end = int(end*freq)
    if end > len(data):
        return data[int(start*freq):]
    return data[int(start*freq):end]


def seconds(data, freq):
    """
    Returns number of seconds from track data based on frequency
    :param track: wav audio data
    :param freq: frequency of audio data
    :return: number of seconds
    """
    return len(data)/freq


def process(data, callback=None):
    """
    Can modify audio signal with callback function applied to every frame of data
    or simply return copy of the track if callback is None
    :param data: wav audio data
    :param callback: method to be invoked every step of track
    :return: copy of track with applied modifications
    """
    if not callback:
        def callback(t):
            return t
    output = np.empty(shape=[len(data)], dtype=np.int16)
    for i in xrange(0, len(data)):
        output.put(i, callback(data[i]))
    return output

""" FILE UTILS """


def save(filename, data, freq):
    """
    Wrapper for scipy.io.wavfile write method
    :param filename: name of wav file
    :param freq: frequency of audio data
    :param data: wav audio data
    """
    wav.write(filename=filename, rate=freq, data=data)

""" DRAW DATA """


def spectrogram(data, freq, NFFT=256, noverlap=128, mode='psd', sides='default'):
    """
    Draws spectrogram of audio file with audio file data using matplotlib specgram method
    minimal arguments are audio data and frequency
    :param data: wav audio data
    :param freq: see matplotlib.specgram Fs - here frequency of audio data
    :param NFFT: see matplotlib.specgram
    :param noverlap: see.matplotlib.specgram
    :param mode: see matplotlib.specgram
    :param sides: see matplotlib.specgram
    :return: see matplotlib.specgram - first parameter is matplotlib.pyplot
    """
    sec = seconds(data, freq)
    xtick = np.linspace(0, sec, num=len(data))
    ax1 = plt.subplot(211)
    plt.plot(xtick, data)
    plt.subplot(212, sharex=ax1)
    spec, f, t, i = plt.specgram(data, NFFT=NFFT, Fs=freq, noverlap=noverlap, mode=mode, sides=sides)
    return (plt, spec, f, t, i)


if __name__ == '__main__':
    print("Will draw spectrogram of given audio file ex. python audio.py test.wav")
    if len(sys.argv) == 2:
        spectrogram(*to_mono(sys.argv[1]))[0].show()