GitHub - bastibe/python-soundfile: SoundFile is an audio library based on libsndfile, CFFI, and NumPy (original) (raw)

python-soundfile

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The soundfile module is an audio library based on libsndfile, CFFI and NumPy. Full documentation is available on https://python-soundfile.readthedocs.io/.

The soundfile module 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 throughCFFI, which is a foreign function interface for Python calling C code. CFFI is supported for CPython 2.6+, 3.x and PyPy 2.0+. The soundfile module represents audio data as NumPy arrays.

python-soundfile is BSD licensed (BSD 3-Clause License).

(c) 2013, Bastian Bechtold

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Breaking Changes

The soundfile module has evolved rapidly in the past. Most notably, we changed the import name from import pysoundfile toimport 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.

In 0.8.0, we changed the default value of always_2d from Trueto False. Also, the order of arguments of the write function changed from write(data, file, ...) to write(file, data, ...).

In 0.9.0, we changed the ctype arguments of the buffer_*methods to dtype, using the Numpy dtype notation. The oldctype arguments still work, but are now officially deprecated.

In 0.12.0, we changed the load order of the libsndfile library. Now, the packaged libsndfile in the platform-specific wheels is tried before falling back to any system-provided libsndfile. If you would prefer using the system-provided libsndfile, install the source package or source wheel instead of the platform-specific wheels.

Installation

The soundfile module depends on the Python packages CFFI and NumPy, and the library libsndfile.

In a modern Python, you can use pip install soundfile to download and install the latest release of the soundfile module and its dependencies. On Windows (64/32) and OS X (Intel/ARM) and Linux 64, this will also install a current version of the library libsndfile. If you install the source module, you need to install libsndfile using your distribution's package manager, for example sudo apt install libsndfile1.

If you are running on an unusual platform or if you are using an older version of Python, you might need to install NumPy and CFFI separately, for example using the Anaconda package manager.

Building

Soundfile itself does not contain any compiled code and can be bundled into a wheel with the usual python setup.py bdist_wheel. However, soundfile relies on libsndfile, and optionally ships its own copy of libsndfile in the wheel.

To build a binary wheel that contains libsndfile, make sure to checkout and update the _soundfile_data submodule, then runpython setup.py bdist_wheel as usual. If the resulting file size of the wheel is around one megabyte, a matching libsndfile has been bundled (without libsndfile, it's around 25 KB).

To build binary wheels for all supported platforms, run python build_wheels.py, which will python setup.py bdist_wheel for each of the platforms we have precompiled libsndfiles for.

Error Reporting

In case of API usage errors the soundfile module raises the usual ValueError or TypeError.

For other errors SoundFileError is raised (used to be RuntimeError). Particularly, a LibsndfileError subclass of this exception is raised on errors reported by the libsndfile library. In that case the exception object provides the libsndfile internal error code in the LibsndfileError.code attribute and the raw libsndfile error message in the LibsndfileError.error_string attribute.

Read/Write Functions

Data can be written to the file using soundfile.write(), or read from the file using soundfile.read(). The soundfile module can open all file formats that libsndfile supports, for example WAV, FLAC, OGG and MAT files (see Known Issues below about writing OGG files).

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

import soundfile as sf

data, samplerate = sf.read('existing_file.wav') sf.write('new_file.flac', data, samplerate)

Block Processing

Sound files can also be read in short, optionally overlapping blocks with soundfile.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 SoundFile.close() method or the context manager to close the file explicitly:

import soundfile as sf

with sf.SoundFile('myfile.wav', 'r+') as f: while f.tell() < f.frames: 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

soundfile.read() can usually auto-detect the file type of sound files. This is not possible for RAW files, though:

import soundfile as sf

data, samplerate = sf.read('myfile.raw', channels=1, samplerate=44100, subtype='FLOAT')

Note that on x86, this defaults to endian='LITTLE'. If you are reading big endian data (mostly old PowerPC/6800-based files), you have to set endian='BIG' accordingly.

You can write RAW files in a similar way, but be advised that in most cases, a more expressive format is better and should be used instead.

Virtual IO

If you have an open file-like object, soundfile.read() 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:

import io import soundfile as sf from urllib.request import urlopen

url = "http://tinyurl.com/shepard-risset" data, samplerate = sf.read(io.BytesIO(urlopen(url).read()))

Note that the above example only works with Python 3.x. For Python 2.x support, replace the third line with:

from urllib2 import urlopen

In-memory files

Chunks of audio, i.e. bytes, can also be read and written without touching the filesystem. In the following example OGG is converted to WAV entirely in memory (without writing files to the disk):

import io import soundfile as sf

def ogg2wav(ogg: bytes): ogg_buf = io.BytesIO(ogg) ogg_buf.name = 'file.ogg' data, samplerate = sf.read(ogg_buf) wav_buf = io.BytesIO() wav_buf.name = 'file.wav' sf.write(wav_buf, data, samplerate) wav_buf.seek(0) # Necessary for .read() to return all bytes return wav_buf.read()

Controlling bitrate mode and compression level

For some audio formats, you can control the bitrate and compression level.

compression_level is a float between 0 and 1, with 1 being the highest compression, and bitrate_mode is 'VARIABLE', 'CONSTANT', or 'AVERAGE'.

import soundfile as sf

for example, this uncompressed 5 minute wav file with 32 kHz sample rate is 18 Mb

data, samplerate = sf.read('5min_32kHz.wav')

maximum mp3 compression results in 1.1 Mb file, with either CONSTANT or VARIABLE bit rate

sf.write('max_compression_vbr.mp3', data, samplerate, bitrate_mode='VARIABLE', compression_level=.99) sf.write('max_compression_cbr.mp3', data, samplerate, bitrate_mode='CONSTANT', compression_level=.99)

minimum mp3 compression results in 3.5 Mb file

sf.write('min_compression_vbr.mp3', data, samplerate, bitrate_mode='VARIABLE', compression_level=0)

Known Issues

Writing to OGG files can result in empty files with certain versions of libsndfile. See #130 for news on this issue.

If using a Buildroot style system, Python has trouble locating libsndfile.so file, which causes python-soundfile to not be loaded. This is apparently a bug in python. For the time being, in soundfile.py, you can remove the call to _find_library and hardcode the location of the libsndfile.so in _ffi.dlopen. See #258 for discussion on this issue.

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!

2015-04-12 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.

2015-10-20 V0.8.0 Bastian Bechtold:

Again, Matthias Geier contributed a whole lot of hard work to this release.

And many more minor bug fixes.

2017-02-02 V0.9.0 Bastian Bechtold:

Thank you, Matthias Geier, Tomas Garcia, and Todd, for contributions for this release.

And some minor bug fixes.

2017-11-12 V0.10.0 Bastian Bechtold:

Thank you, Matthias Geier, Toni Barth, Jon Peirce, Till Hoffmann, and Tomas Garcia, for contributions to this release.

2022-06-02 V0.11.0 Bastian Bechtold:

Thank you, tennies, Hannes Helmholz, Christoph Boeddeker, Matt Vollrath, Matthias Geier, Jacek Konieczny, Boris Verkhovskiy, Jonas Haag, Eduardo Moguillansky, Panos Laganakos, Jarvy Jarvison, Domingo Ramirez, Tim Chagnon, Kyle Benesch, Fabian-Robert Stöter, Joe Todd

2023-02-02 V0.12.0 Bastian Bechtold

Thank you, Barabazs, Andrew Murray, Jon Peirce, for contributions to this release.

2023-02-15 V0.12.1 Bastian Bechtold

Thank you, funnypig, for the bug report

2025-01-02 V0.13.0 Bastian Bechtold

Thank you, Zhong Jianxin, mcclure, jneuendorf-i4h, aoirint, endolith, Guy Illes, ytya, Sam Lapp, Benjamin Moody

2025-01-25 V0.13.1 Bastian Bechtold

Thank you, Brian McFee and Guy Illes