PySoundFile 0.6.0

An audio library based on libsndfile, CFFI and NumPy


Platform: Pypi

Language: Python

License: BSD-3-Clause-Clear

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PySoundFile is an audio library based on libsndfile, CFFI and Numpy. Full documentation is available on

PySoundFile can read and write sound files. File reading/writing is supported through libsndfile, which is a free, cross-platform, open-source (LGPL) library for reading and writing many different sampled sound file formats that runs on many platforms including Windows, OS X, and Unix. It is accessed through CFFI, which is a foreign function interface for Python calling C code. CFFI is supported for CPython 2.6+, 3.x and PyPy 2.0+. PySoundFile represents audio data as NumPy arrays.

PySoundFile is BSD licensed (BSD 3-Clause License).
(c) 2013, Bastian Bechtold

Breaking Changes

The latest release of PySoundFile cleans up many small inconsistencies, particularly in the the ordering and naming of function arguments. Therefore, old code will probably not work any more.

It also adds a number of great new features, such as global read and write functions that do not require you to open a SoundFile, or a blocks function that can read a sound file one block at a time. It has also grown a lot more flexible and powerful at opening things like streams, buffers, or file descriptors.

With all these improvements, we feel that the indexing interface is not needed any more. It is now officially marked as deprecated and might be removed in the future.


PySoundFile depends on the Python packages CFFI and Numpy, and the system library libsndfile.

To install the Python dependencies, I recommend using the Anaconda Distribution of Python. Anaconda provides the conda package manager, which will install all dependencies using conda install cffi numpy (conda is also independently available on pip).

You will also need to install libsndfile. On Windows, libsndfile is included in the binary installers (see below). On OS X, homebrew can install libsndfile using brew install libsndfile. On Linux, use your distribution's package manager, for example sudo apt-get install libsndfile.

With CFFI, Numpy, and libsndfile installed, you can use pip to install PySoundFile with pip install pysoundfile or pip install pysoundfile --user if you don't have administrator privileges. If you are running Windows you should download the Windows installers for PySoundFile instead (which also include libsndfile):

Read/Write Functions

Data can be written to the file using write(), or read from the file using read(). PySoundFile can open all file formats that libsndfile supports, for example WAV, FLAC, OGG and MAT files.

Here is an example for a program that reads a wave file and copies it into an ogg-vorbis file:

import soundfile as sf
data, samplerate ='existing_file.wav')
sf.write(data, 'new_file.ogg', samplerate=samplerate)

Block Processing

Sound files can also be read in short, optionally overlapping blocks. For example, this calculates the signal level for each block of a long file:

import numpy as np
import soundfile as sf
rms = [np.sqrt(np.mean(block**2)) for block in
 sf.blocks('myfile.wav', blocksize=1024, overlap=512)]

SoundFile Objects

Sound files can also be opened as SoundFile objects. Every SoundFile has a specific sample rate, data format and a set number of channels.

If a file is opened, it is kept open for as long as the SoundFile object exists. The file closes when the object is garbage collected, but you should use the close() method or the context manager to close the file explicitly:

import soundfile as sf
with sf.SoundFile('myfile.wav', 'rw') as f:
 while f.tell() < len(f):
 pos = f.tell()
 data =

All data access uses frames as index. A frame is one discrete time-step in the sound file. Every frame contains as many samples as there are channels in the file.

RAW Files

Pysoundfile can usually auto-detect the file type of sound files. This is not possible for RAW files, though. This is a useful idiom for opening RAW files without having to provide all the format for every file:

import soundfile as sf
format = {'format':'RAW', 'subtype':'FLOAT', 'endian':'FILE'}
data ='myfile.raw', dtype='float32', **format)
sf.write(data, 'otherfile.raw', **format)

Virtual IO

If you have an open file-like object, Pysoundfile can open it just like regular files:

import soundfile as sf
with open('filename.flac', 'rb') as f:
 data, samplerate =

Here is an example using an HTTP request:

from io import BytesIO
import soundfile as sf
import requests
f = BytesIO()
response = requests.get('', stream=True)
for data in response.iter_content(4096):
 if data:
data, samplerate =

Accessing File Metadata

In addition to audio data, there are a number of text fields in some sound files. In particular, you can set a title, a copyright notice, a software description, the artist name, a comment, a date, the album name, a license, a track number and a genre. Note however, that not all of these fields are supported for every file format.


2013-08-27 V0.1.0 Bastian Bechtold:
Initial prototype. A simple wrapper for libsndfile in Python
2013-08-30 V0.2.0 Bastian Bechtold:
Bugfixes and more consistency with PySoundCard
2013-08-30 V0.2.1 Bastian Bechtold:
2013-09-27 V0.3.0 Bastian Bechtold:
Added binary installer for Windows, and context manager
2013-11-06 V0.3.1 Bastian Bechtold:
Switched from distutils to setuptools for easier installation
2013-11-29 V0.4.0 Bastian Bechtold:
Thanks to David Blewett, now with Virtual IO!
2013-12-08 V0.4.1 Bastian Bechtold:
Thanks to Xidorn Quan, FLAC files are not float32 any more.
2014-02-26 V0.5.0 Bastian Bechtold:
Thanks to Matthias Geier, improved seeking and a flush() method.
2015-01-19 V0.6.0 Bastian Bechtold:

A big, big thank you to Matthias Geier, who did most of the work!

  • Switched to float64 as default data type.
  • Function arguments changed for consistency.
  • Added unit tests.
  • Added global read(), write(), blocks() convenience functions.
  • Documentation overhaul and hosting on readthedocs.
  • Added 'x' open mode.
  • Added tell() method.
  • Added __repr__() method.
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GitHub Repository

bastibe/PySoundFile bastibe/PySoundFile

PySoundFile is an audio library based on libsndfile, CFFI, and NumPy

Language: Python

Created: August 27, 2013 13:36

Last updated: March 30, 2015 03:05

Last pushed: March 29, 2015 21:59

Size: 5.34 MB

Stars: 28

Forks: 6

Watchers: 4

Open issues: 19

Top Contributors

Matthias Geier Bastian Bechtold David Blewett Xidorn Quan Nils Werner Sebastian


  • 0.6.0 - January 19, 2015 16:50
  • 0.5.0 - February 26, 2014 17:05
  • 0.4.1 - December 08, 2013 10:02
  • 0.4.0 - November 29, 2013 16:49
  • 0.3.1 - November 06, 2013 16:23
  • 0.3 - October 11, 2013 10:15
  • 0.2.1 - August 30, 2013 09:25
  • 0.2 - August 30, 2013 08:14
  • 0.1 - August 27, 2013 13:43

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