Audio Effects

Multiple types of audio effects will be described and implemented in python.

Table of Contents

• Getting Started
• Playing Files
• Using Pyaudio
• Effects
• Blocking
• Callback
• Visualization with Pyplot

Getting Started

All of these implementations will be in python and therefore will utilize the pyaudio module. I would suggest to use python 2.7 since some of the other modules I will be using will not be compatible with the 3+ version. By default, pip and setuptools will already be installed however they will need to be upgraded:

For windows:

python -m pip install -U pip setuptools

For Linux or OSX:

sudo pip install -U pip setuptools

For those with faith:
You can download this python script which should install pip upon running:

python get-python.py

Now, in order to install the pyaudio module simply type the following into the terminal:

sudo pip install pyaudio

If you run into an error, you may have to install manually by downloading the corresponding wheel and using pip. The wheels can be found at http://www.lfd.uci.edu/~gohlke/pythonlibs/

In order to install, simply download the wheel and move it to your current directory. Then type:

pip install (Name of your wheel).whl

Playing files

Initialize:

p = pyaudio.PyAudio()

stream = p.open(format      = pyaudio.paInt16,
                channels    = num_channels,
                rate        = Fs,
                input       = False,
                output      = True )

Reading/Editing/Playing:

input_string = wf.readframes(1)          # Get first frame
while input_string != '':

    # Convert string to number
    input_tuple = struct.unpack('h', input_string)  # One-element tuple
    input_value = input_tuple[0]                    # Extract number from tuple

    # Compute output value
    output_value = gain * input_value               # Multiple value by set gain

    # Convert output value to binary string
    output_string = struct.pack('h', output_value)  

    # Write output value to audio stream
    stream.write(output_string)                     

    # Get next frame
    input_string = wf.readframes(1) 

Using Pyaudio

Effects

• Amplitude modulation
• Complex Amplitude modulation
• Delay
• Delay with Feedback
• Ping-pong effect
• Virbrato

Blocking

Callback

Visualization with Pyplot