PySoundFile 0.6.0

An audio library based on libsndfile, CFFI and NumPy

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

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.

Installation

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):

PySoundFile-0.6.0.win-amd64-py2.7

PySoundFile-0.6.0.win-amd64-py3.4

PySoundFile-0.6.0.win32-py2.7

PySoundFile-0.6.0.win32-py3.4

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 pysoundfile as sf

data, samplerate = sf.read('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 pysoundfile 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 pysoundfile as sf

with sf.SoundFile('myfile.wav', 'rw') as f:
    while f.tell() < len(f):
        pos = f.tell()
        data = f.read(1024)
        f.seek(pos)
        f.write(data*2)

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 pysoundfile as sf

format = {'format':'RAW', 'subtype':'FLOAT', 'endian':'FILE'}
data = sf.read('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 pysoundfile as sf
with open('filename.flac', 'rb') as f:
    data, samplerate = sf.read(f)

Here is an example using an HTTP request:

from io import BytesIO
import pysoundfile as sf
import requests

f = BytesIO()
response = requests.get('http://www.example.com/my.flac', stream=True)
for data in response.iter_content(4096):
    if data:
        f.write(data)
f.seek(0)
data, samplerate = sf.read(f)

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.

News

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:

Bugfixes

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.