pya

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What is pya?

pya is a package to support creation and manipulation of audio signals with Python. It uses numpy arrays to store and compute audio signals.

• Documentation: see examples/pya-examples.ipynb for a quick tutorial and Documentation
• Source code: https://github.com/interactive-sonification/pya

It provides:

• Asig - a versatile audio signal class
  • Ugen - a subclass of Asig, which offers unit generators such as sine, square, sawtooth, noise
• Aserver - an audio server class for queuing and playing Asigs
• Arecorder - an audio recorder class
• Aspec - an audio spectrum class, using rfft as real-valued signals are always implied
• Astft - an audio STFT (short-term Fourier transform) class
• A number of helper functions, e.g. device_info()

pya can be used for

• multi-channel audio processing
• auditory display and sonification
• sound synthesis experiment
• audio applications in general such as games or GUI-enhancements
• signal analysis and plotting

At this time pya is more suitable for offline rendering than realtime.

Authors and Contributors

• Thomas (author, maintainer)
• Jiajun (co-author, maintainer)
• Alexander (maintainer)
• Contributors will be acknowledged here, contributions are welcome.

Installation

pya requires portaudio and its Python wrapper PyAudio to play and record audio.

Using Conda

Pyaudio can be installed via conda:

conda install pyaudio

Disclaimer: Python 3.10+ requires PyAudio 0.2.12 which is not available on Conda as of December 2022. Conda-forge provides a version only for Linux at the moment. Users of Python 3.10 should for now use other installation options.

Using Homebrew and PIP (MacOS only)

brew install portaudio

Then

pip install pya

For Apple ARM Chip, if you failed to install the PyAudio dependency, you can follow this guide: Installation on ARM chip

• Option 1: Create .pydistutils.cfg in your home directory, ~/.pydistutils.cfg, add:

  echo "[build_ext]
  include_dirs=$(brew --prefix portaudio)/include/
  library_dirs=$(brew --prefix portaudio)/lib/" > ~/.pydistutils.cfg
  

  Use pip:

  pip install pya
  

  You can remove the .pydistutils.cfg file after installation.

• Option 2: Use CFLAGS:

  CFLAGS="-I/opt/homebrew/include -L/opt/homebrew/lib" pip install pya
  

Using PIP (Linux)

Try sudo apt-get install portaudio19-dev or equivalent to your distro, then

pip isntall pya

Using PIP (Windows)

PyPI provides PyAudio wheels for Windows including portaudio:

pip install pyaudio

should be sufficient.

A simple example

Startup:

import pya
s = pya.Aserver(bs=1024)
pya.Aserver.default = s  # to set as default server
s.boot()

Create an Asig signal:

A 1s / 440 Hz sine tone at sampling rate 44100 as channel name 'left':

import numpy as np
signal_array = np.sin(2 * np.pi * 440 * np.linspace(0, 1, 44100))
atone = pya.Asig(signal_array, sr=44100, label='1s sine tone', cn=['left'])

Other ways of creating an Asig object:

asig_int = pya.Asig(44100, sr=44100)  # zero array with 44100 samples
asig_float = pya.Asig(2., sr=44100)  # float argument, 2 seconds of zero array
asig_str = pya.Asig('./song.wav')  # load audio file
asig_ugen = pya.Ugen().square(freq=440, sr=44100, dur=2., amp=0.5)  # using Ugen class to create common waveforms

Audio files are also possible using the file path. WAV should work without issues. MP3 is supported but may raise error if FFmpeg.

If you use Anaconda, installation is quite easy:

conda install -c conda-forge ffmpeg

Otherwise:

• Mac or Linux with brew
  • brew install ffmpeg
• On Linux
  • Install FFmpeg via apt-get: sudo apt install ffmpeg
• On Windows
  • Download the latest distribution from https://ffmpeg.zeranoe.com/builds/
  • Unzip the folder, preferably to C:\
  • Append the FFmpeg binary folder (e.g. C:\ffmpeg\bin) to the PATH system variable (How do I set or change the PATH system variable?)

Key attributes

• atone.sig --> The numpy array containing the signal is
• atone.sr --> the sampling rate
• atone.cn --> the list of custom defined channel names
• atone.label --> a custom set identifier string

Play signals

atone.play(server=s)  

play() uses Aserver.default if server is not specified

Instead of specifying a long standing server. You can also use Aserver as a context:

with pya.Aserver(sr=48000, bs=256, channels=2) as aserver:
    atone.play(server=aserver)  # Or do: aserver.play(atone)

The benefit of this is that it will handle server bootup and shutdown for you. But notice that server up/down introduces extra latency.

Play signal on a specific device

from pya import find_device
from pya import Aserver
devices = find_device() # This will return a dictionary of all devices, with their index, name, channels.
s = Aserver(sr=48000, bs=256, device=devices['name_of_your_device']['index'])

Plotting signals

to plot the first 1000 samples:

atone[:1000].plot()

to plot the magnitude and phase spectrum:

atone.plot_spectrum()

to plot the spectrum via the Aspec class

atone.to_spec().plot()

to plot the spectrogram via the Astft class

atone.to_stft().plot(ampdb)

Selection of subsets

• Asigs support multi-channel audio (as columns of the signal array)
  • a1[:100, :3] would select the first 100 samples and the first 3 channels,
  • a1[{1.2:2}, ['left']] would select the channel named 'left' using a time slice from 1

Recording from Device

Arecorder allows recording from input device

import time

from pya import find_device
from pya import Arecorder
devices = find_device()  # Find the index of the input device
arecorder = Arecorder(device=some_index, sr=48000, bs=512)  # Or not set device to let pya find the default device 
arecorder.boot()
arecorder.record()
time.sleep(2)  # Recording is non-blocking
arecorder.stop()
last_recording = arecorder.recordings[-1]  # Each time a recorder stop, a new recording is appended to recordings

Method chaining

Asig methods usually return an Asig, so methods can be chained, e.g

atone[{0:1.5}].fade_in(0.1).fade_out(0.8).gain(db=-6).plot(lw=0.1).play(rate=0.4, onset=1)

Learning more

• Please check the examples/pya-examples.ipynb for more examples and details.

Contributing

• Please get in touch with us if you wish to contribute. We are happy to be involved in the discussion of new features and to receive pull requests.