genaudio.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Simple script to generate test MP3 files

https://stackoverflow.com/questions/33879523/python-how-can-i-generate-a-wav-file-with-beeps
"""

import math
import wave
import struct
import os

# Audio will contain a long list of samples (i.e. floating point numbers describing the
# waveform).  If you were working with a very long sound you'd want to stream this to
# disk instead of buffering it all in memory list this.  But most sounds will fit in 
# memory.
audio = []
sample_rate = 44100.0


def append_silence(duration_milliseconds=500):
    """
    Adding silence is easy - we add zeros to the end of our array
    """
    num_samples = duration_milliseconds * (sample_rate / 1000.0)

    for x in range(int(num_samples)): 
        audio.append(0.0)

    return


def append_sinewave(
        freq=440.0, 
        duration_milliseconds=500, 
        volume=1.0):
    """
    The sine wave generated here is the standard beep.  If you want something
    more aggresive you could try a square or saw tooth waveform.   Though there
    are some rather complicated issues with making high quality square and
    sawtooth waves... which we won't address here :) 
    """ 

    global audio # using global variables isn't cool.

    num_samples = duration_milliseconds * (sample_rate / 1000.0)

    for x in range(int(num_samples)):
        audio.append(volume * math.sin(2 * math.pi * freq * ( x / sample_rate )))

    return

def combine_sinewave(
        freqs=[440.0,880], 
        duration_milliseconds=500, 
        volume=1.0):
    """
    The sine wave generated here is the standard beep.  If you want something
    more aggresive you could try a square or saw tooth waveform.   Though there
    are some rather complicated issues with making high quality square and
    sawtooth waves... which we won't address here :) 
    """ 

    global audio # using global variables isn't cool.

    num_samples = duration_milliseconds * (sample_rate / 1000.0)

    for x in range(int(num_samples)):
        ssum = 0
        for freq in freqs:
            ssum += volume * math.sin(2 * math.pi * freq * ( x / sample_rate ))
        audio.append(ssum)

    return


def save_wav(file_name):
    # Open up a wav file
    wav_file=wave.open(file_name,"w")

    # wav params
    nchannels = 1

    sampwidth = 2

    # 44100 is the industry standard sample rate - CD quality.  If you need to
    # save on file size you can adjust it downwards. The stanard for low quality
    # is 8000 or 8kHz.
    nframes = len(audio)
    comptype = "NONE"
    compname = "not compressed"
    wav_file.setparams((nchannels, sampwidth, sample_rate, nframes, comptype, compname))

    # WAV files here are using short, 16 bit, signed integers for the 
    # sample size.  So we multiply the floating point data we have by 32767, the
    # maximum value for a short integer.  NOTE: It is theortically possible to
    # use the floating point -1.0 to 1.0 data directly in a WAV file but not
    # obvious how to do that using the wave module in python.
    for sample in audio:
        wav_file.writeframes(struct.pack('h', int( sample * 32767.0 )))

    wav_file.close()

    return


combine_sinewave(volume=0.5,freqs=[0,2000])
append_silence()
combine_sinewave(volume=0.5,freqs=[1000,2000])
append_silence()
# append_sinewave(volume=0.5,freq=1000)
# append_silence()
# append_sinewave()
filename = "beep"
save_wav(f"{filename}.wav")


# Convert wav to mp3
os.system(f"ffmpeg -i {filename}.wav {filename}.mp3 -y")
# Remove wav file
os.system(f"rm {filename}.wav")