pysndfile
=========

pysndfile is a python package providing *PySndfile*, a
`Cython <http://cython.org/>`__ wrapper class around
`libsndfile <http://www.mega-nerd.com/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 <http://anasynth.ircam.fr/home/english>`__ 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).

Implementation
--------------

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.

Changes
-------

Version 0.2.9
~~~~~~~~~~~~~

-  Added missing files to distribution.
-  force current cythonized version to be distributed.

Version 0.2.4
~~~~~~~~~~~~~

-  Compatibility with python 3 (thanks to Eduardo Moguillansky)
-  bug fix: ensure that vectors returned by read\_frames function own
   their data.

Copyright
---------

Copyright (C) 2014 IRCAM

Author
------

Axel Roebel

Credits:
--------

Erik de Castro Lopo: for
`libsndfile <http://www.mega-nerd.com/libsndfile/>`__

David Cournapeau: for a few ideas I gathered from
`scikits.audiolab <http://cournape.github.io/audiolab/>`__.

The `Cython <http://cython.org>`__ maintainers for the efficient means
to write interface definitions in Cython.
