PySoundFile

PySoundFile is an audio library based on libsndfile, CFFI and NumPy. Full documentation is available on http://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

PySoundFile has evolved rapidly during the last few releases. Most notably, we changed the import name from import pysoundfile to import soundfile in 0.7. In 0.6, we cleaned up many small inconsistencies, particularly in the the ordering and naming of function arguments and the removal of the indexing interface.

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 3. This will come with all dependencies pre-installed. To install the dependencies manually, you can use the conda package manager, which will install all dependencies using conda install cffi numpy (conda is also available independently of Anaconda with pip install conda; conda init).

With CFFI and NumPy installed, you can use pip install pysoundfile to download and install the latest release of PySoundFile. On Windows and OS X, this will also install the library libsndfile. On Linux, you need to install libsndfile using your distribution’s package manager, for example sudo apt-get install libsndfile1.

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 = 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 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 = 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 soundfile 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 soundfile 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 soundfile 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)

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.
2015-04-xx V0.7.0 Bastian Bechtold:

Again, thanks to Matthias Geier for all of his hard work, but also Nils Werner and Whistler7 for their many suggestions and help.

  • Renamed import pysoundfile to import soundfile.
  • Installation through pip wheels that contain the necessary libraries for OS X and Windows.
  • Removed exclusive_creation argument to write.
  • Added truncate() method.

API Documentation

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

Sound files can be read or written directly using the functions read() and write(). To read a sound file in a block-wise fashion, use blocks(). Alternatively, sound files can be opened as SoundFile objects.

For further information, see http://pysoundfile.readthedocs.org/.

soundfile.read(file, frames=-1, start=0, stop=None, dtype='float64', always_2d=True, fill_value=None, out=None, samplerate=None, channels=None, format=None, subtype=None, endian=None, closefd=True)[source]

Provide audio data from a sound file as NumPy array.

By default, the whole file is read from the beginning, but the position to start reading can be specified with start and the number of frames to read can be specified with frames. Alternatively, a range can be specified with start and stop.

If there is less data left in the file than requested, the rest of the frames are filled with fill_value. If no fill_value is specified, a smaller array is returned.

Parameters:
  • file (str or int or file-like object) – The file to read from. See SoundFile for details.
  • frames (int, optional) – The number of frames to read. If frames is negative, the whole rest of the file is read. Not allowed if stop is given.
  • start (int, optional) – Where to start reading. A negative value counts from the end.
  • stop (int, optional) – The index after the last frame to be read. A negative value counts from the end. Not allowed if frames is given.
  • dtype ({'float64', 'float32', 'int32', 'int16'}, optional) – Data type of the returned array, by default 'float64'. Floating point audio data is typically in the range from -1.0 to 1.0. Integer data is in the range from -2**15 to 2**15-1 for 'int16' and from -2**31 to 2**31-1 for 'int32'.
Returns:

  • audiodata (numpy.ndarray or type(out)) – A two-dimensional NumPy array is returned, where the channels are stored along the first dimension, i.e. as columns. A two-dimensional array is returned even if the sound file has only one channel. Use always_2d=False to return a one-dimensional array in this case.

    If out was specified, it is returned. If out has more frames than available in the file (or if frames is smaller than the length of out) and no fill_value is given, then only a part of out is overwritten and a view containing all valid frames is returned.

  • samplerate (int) – The sample rate of the audio file.
Other Parameters:
 
  • always_2d (bool, optional) – By default, audio data is always returned as a two-dimensional array, even if the audio file has only one channel. With always_2d=False, reading a mono sound file will return a one-dimensional array.
  • fill_value (float, optional) – If more frames are requested than available in the file, the rest of the output is be filled with fill_value. If fill_value is not specified, a smaller array is returned.
  • out (numpy.ndarray or subclass, optional) – If out is specified, the data is written into the given array instead of creating a new array. In this case, the arguments dtype and always_2d are silently ignored! If frames is not given, it is obtained from the length of out.
  • samplerate, channels, format, subtype, endian, closefd – See SoundFile.

Examples

>>> import soundfile as sf
>>> data, samplerate = sf.read('stereo_file.wav')
>>> data
array([[ 0.71329652,  0.06294799],
       [-0.26450912, -0.38874483],
       ...
       [ 0.67398441, -0.11516333]])
>>> samplerate
44100
soundfile.write(data, file, samplerate, subtype=None, endian=None, format=None, closefd=True)[source]

Write data to a sound file.

Note

If file exists, it will be truncated and overwritten!

Parameters:
  • data (array_like) –

    The data to write. Usually two-dimensional (channels x frames), but one-dimensional data can be used for mono files. Only the data types 'float64', 'float32', 'int32' and 'int16' are supported.

    Note

    The data type of data does not select the data type of the written file. Audio data will be converted to the given subtype.

  • file (str or int or file-like object) – The file to write to. See SoundFile for details.
  • samplerate (int) – The sample rate of the audio data.
  • subtype (str, optional) – See default_subtype() for the default value and available_subtypes() for all possible values.
Other Parameters:
 

format, endian, closefd – See SoundFile.

Examples

Write 10 frames of random data to a file:

>>> import numpy as np
>>> import soundfile as sf
>>> sf.write(np.random.randn(10, 2), 'stereo_file.wav', 44100, 'PCM_24')
soundfile.blocks(file, blocksize=None, overlap=0, frames=-1, start=0, stop=None, dtype='float64', always_2d=True, fill_value=None, out=None, samplerate=None, channels=None, format=None, subtype=None, endian=None, closefd=True)[source]

Return a generator for block-wise reading.

By default, iteration starts at the beginning and stops at the end of the file. Use start to start at a later position and frames or stop to stop earlier.

If you stop iterating over the generator before it’s exhausted, the sound file is not closed. This is normally not a problem because the file is opened in read-only mode. To close the file properly, the generator’s close() method can be called.

Parameters:
  • file (str or int or file-like object) – The file to read from. See SoundFile for details.
  • blocksize (int) – The number of frames to read per block. Either this or out must be given.
  • overlap (int, optional) – The number of frames to rewind between each block.
Yields:

numpy.ndarray or type(out) – Blocks of audio data. If out was given, and the requested frames are not an integer multiple of the length of out, and no fill_value was given, the last block will be a smaller view into out.
Other Parameters:
 
  • frames, start, stop – See read().
  • dtype ({‘float64’, ‘float32’, ‘int32’, ‘int16’}, optional) – See read().
  • always_2d, fill_value, out – See read().
  • samplerate, channels, format, subtype, endian, closefd – See SoundFile.

Examples

>>> import soundfile as sf
>>> for block in sf.blocks('stereo_file.wav', blocksize=1024):
>>>     pass  # do something with 'block'
soundfile.available_formats()[source]

Return a dictionary of available major formats.

Examples

>>> import soundfile as sf
>>> sf.available_formats()
{'FLAC': 'FLAC (FLAC Lossless Audio Codec)',
 'OGG': 'OGG (OGG Container format)',
 'WAV': 'WAV (Microsoft)',
 'AIFF': 'AIFF (Apple/SGI)',
 ...
 'WAVEX': 'WAVEX (Microsoft)',
 'RAW': 'RAW (header-less)',
 'MAT5': 'MAT5 (GNU Octave 2.1 / Matlab 5.0)'}
soundfile.available_subtypes(format=None)[source]

Return a dictionary of available subtypes.

Parameters:format (str) – If given, only compatible subtypes are returned.

Examples

>>> import soundfile as sf
>>> sf.available_subtypes('FLAC')
{'PCM_24': 'Signed 24 bit PCM',
 'PCM_16': 'Signed 16 bit PCM',
 'PCM_S8': 'Signed 8 bit PCM'}
soundfile.check_format(format, subtype=None, endian=None)[source]

Check if the combination of format/subtype/endian is valid.

Examples

>>> import soundfile as sf
>>> sf.check_format('WAV', 'PCM_24')
True
>>> sf.check_format('FLAC', 'VORBIS')
False
soundfile.default_subtype(format)[source]

Return the default subtype for a given format.

Examples

>>> import soundfile as sf
>>> sf.default_subtype('WAV')
'PCM_16'
>>> sf.default_subtype('MAT5')
'DOUBLE'
class soundfile.SoundFile(file, mode='r', samplerate=None, channels=None, subtype=None, endian=None, format=None, closefd=True)[source]

Open a sound file.

If a file is opened with mode 'r' (the default) or 'r+', no sample rate, channels or file format need to be given because the information is obtained from the file. An exception is the 'RAW' data format, which always requires these data points.

File formats consist of three case-insensitive strings:

  • a major format which is by default obtained from the extension of the file name (if known) and which can be forced with the format argument (e.g. format='WAVEX').
  • a subtype, e.g. 'PCM_24'. Most major formats have a default subtype which is used if no subtype is specified.
  • an endian-ness, which doesn’t have to be specified at all in most cases.

A SoundFile object is a context manager, which means if used in a “with” statement, close() is automatically called when reaching the end of the code block inside the “with” statement.

Parameters:
  • file (str or int or file-like object) – The file to open. This can be a file name, a file descriptor or a Python file object (or a similar object with the methods read()/readinto(), write(), seek() and tell()).
  • mode ({'r', 'r+', 'w', 'w+', 'x', 'x+'}, optional) – Open mode. Has to begin with one of these three characters: 'r' for reading, 'w' for writing (truncates file) or 'x' for writing (raises an error if file already exists). Additionally, it may contain '+' to open file for both reading and writing. The character 'b' for binary mode is implied because all sound files have to be opened in this mode. If file is a file descriptor or a file-like object, 'w' doesn’t truncate and 'x' doesn’t raise an error.
  • samplerate (int) – The sample rate of the file. If mode contains 'r', this is obtained from the file (except for 'RAW' files).
  • channels (int) – The number of channels of the file. If mode contains 'r', this is obtained from the file (except for 'RAW' files).
  • subtype (str, sometimes optional) – The subtype of the sound file. If mode contains 'r', this is obtained from the file (except for 'RAW' files), if not, the default value depends on the selected format (see default_subtype()). See available_subtypes() for all possible subtypes for a given format.
  • endian ({'FILE', 'LITTLE', 'BIG', 'CPU'}, sometimes optional) – The endian-ness of the sound file. If mode contains 'r', this is obtained from the file (except for 'RAW' files), if not, the default value is 'FILE', which is correct in most cases.
  • format (str, sometimes optional) – The major format of the sound file. If mode contains 'r', this is obtained from the file (except for 'RAW' files), if not, the default value is determined from the file extension. See available_formats() for all possible values.
  • closefd (bool, optional) – Whether to close the file descriptor on close(). Only applicable if the file argument is a file descriptor.

Examples

>>> from soundfile import SoundFile

Open an existing file for reading:

>>> myfile = SoundFile('existing_file.wav')
>>> # do something with myfile
>>> myfile.close()

Create a new sound file for reading and writing using a with statement:

>>> with SoundFile('new_file.wav', 'x+', 44100, 2) as myfile:
>>>     # do something with myfile
>>>     # ...
>>>     assert not myfile.closed
>>>     # myfile.close() is called automatically at the end
>>> assert myfile.closed
name

The file name of the sound file.

mode

The open mode the sound file was opened with.

samplerate

The sample rate of the sound file.

channels

The number of channels in the sound file.

format

The major format of the sound file.

subtype

The subtype of data in the the sound file.

endian

The endian-ness of the data in the sound file.

format_info

A description of the major format of the sound file.

subtype_info

A description of the subtype of the sound file.

sections

The number of sections of the sound file.

closed

Whether the sound file is closed or not.

seekable()[source]

Return True if the file supports seeking.

seek(frames, whence=0)[source]

Set the read/write position.

Parameters:
  • frames (int) – The frame index or offset to seek.
  • whence ({SEEK_SET, SEEK_CUR, SEEK_END}, optional) – By default (whence=SEEK_SET), frames are counted from the beginning of the file. whence=SEEK_CUR seeks from the current position (positive and negative values are allowed for frames). whence=SEEK_END seeks from the end (use negative value for frames).
Returns:

int – The new absolute read/write position in frames.

Examples

>>> from soundfile import SoundFile, SEEK_END
>>> myfile = SoundFile('stereo_file.wav')

Seek to the beginning of the file:

>>> myfile.seek(0)
0

Seek to the end of the file:

>>> myfile.seek(0, SEEK_END)
44100  # this is the file length
tell()[source]

Return the current read/write position.

read(frames=-1, dtype='float64', always_2d=True, fill_value=None, out=None)[source]

Read from the file and return data as NumPy array.

Reads the given number of frames in the given data format starting at the current read/write position. This advances the read/write position by the same number of frames. By default, all frames from the current read/write position to the end of the file are returned. Use seek() to move the current read/write position.

Parameters:
  • frames (int, optional) – The number of frames to read. If frames < 0, the whole rest of the file is read.
  • dtype ({'float64', 'float32', 'int32', 'int16'}, optional) – See read().
Returns:

numpy.ndarray or type(out) – The read data; either a new array or out or a view into out. See read() for details.
Other Parameters:
 

always_2d, fill_value, out – See read().

Examples

>>> from soundfile import SoundFile
>>> myfile = SoundFile('stereo_file.wav')

Reading 3 frames from a stereo file:

>>> myfile.read(3)
array([[ 0.71329652,  0.06294799],
       [-0.26450912, -0.38874483],
       [ 0.67398441, -0.11516333]])
>>> myfile.close()
write(data)[source]

Write audio data to the file.

Writes a number of frames at the read/write position to the file. This also advances the read/write position by the same number of frames and enlarges the file if necessary.

Parameters:data (array_like) – See write().
blocks(blocksize=None, overlap=0, frames=-1, dtype='float64', always_2d=True, fill_value=None, out=None)[source]

Return a generator for block-wise reading.

By default, the generator yields blocks of the given blocksize (using a given overlap) until the end of the file is reached; frames can be used to stop earlier.

Parameters:
  • blocksize (int) – The number of frames to read per block. Either this or out must be given.
  • overlap (int, optional) – The number of frames to rewind between each block.
  • frames (int, optional) – The number of frames to read. If frames < 1, the file is read until the end.
  • dtype ({'float64', 'float32', 'int32', 'int16'}, optional) – See read().
Yields:

numpy.ndarray or type(out) – Blocks of audio data. See blocks() for details.
Other Parameters:
 

always_2d, fill_value, out – See read().
truncate(frames=None)[source]

Truncate the file to a given number of frames.

After this command, the read/write position will be at the new end of the file.

Parameters:frames (int, optional) – Only the data before frames is kept, the rest is deleted. If not specified, the current read/write position is used.
flush()[source]

Write unwritten data to the file system.

Data written with write() is not immediately written to the file system but buffered in memory to be written at a later time. Calling flush() makes sure that all changes are actually written to the file system.

This has no effect on files opened in read-only mode.

close()[source]

Close the file. Can be called multiple times.

Index