pysndfile is a python package providing PySndfile, a Cython wrapper class around libsndfile. PySndfile provides methods for reading and writing a large variety of soundfile formats on a variety of plattforms. PySndfile provides a rather complete access to the different sound file manipulation options that are available in libsndfile.
Due to the use of libsndfile nearly all sound file formats, (besides mp3 and derived formats) can be read and written with PySndfile.
The interface has been designed such that a rather large subset of the functionality of libsndfile can be used, notably the reading and writing of strings into soundfile formats that support these, and a number of sf_commands that allow to control the way libsndfile reads and writes the samples. One of the most important ones is the use of the clipping command.
Transparent soundfile io with libsndfile
PySndfile has been developed in the analysis synthesis team at IRCAM mainly for research on sound analysis and sound transformation. In this context it is essential that the reading and writing of soundfile data is transparent.
The use of the clipping mode of libsndfile is important here because reading and writing sound data should not change the audio samples. By default, when clipping is off, libsndfile uses slightly different scaling factors when reading pcm format into float samples, or when writing float samples into pcm format. Therefore whenever a complete read/write cycle is applied to a sound file then the audio samples may be modified even when no processing is applied.
More precisely this will happen if
- the sound files contains pcm format,
- and the data is read into float or double,
- and the audio data comes close to the maximum range such that the difference in scaling leads to modification.
To avoid this problem PySndfile sets clipping by default to on. If you don't like this you can set it to off individually using the PySndfile method set_auto_clipping(False).
The implementation is based on a slightly modified version of the header sndfile.hh that is distributed with libsndfile. The only modification is the addition of a methode querying the seekable state of the open Sndfile.
- setup.py: fixed problem with compilers not providing the compiler attribute (MSVC) (Thanks to Felix Hanke for reporting the problem)
- _pysndfile.pyx: fixed problem when deriving from PySndfile using a modified list of init parameters in the derived class (Thanks to Sam Perry for the suggestion).
- setup.py: rebuild LONG_DESC only if sdist method is used.
- Added missing files to distribution.
- force current cythonized version to be distributed.
- Compatibility with python 3 (thanks to Eduardo Moguillansky)
- bug fix: ensure that vectors returned by read_frames function own their data.
Copyright (C) 2014 IRCAM
Erik de Castro Lopo: for libsndfile
David Cournapeau: for a few ideas I gathered from scikits.audiolab.
The Cython maintainers for the efficient means to write interface definitions in Cython.