pysndfile intro¶
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).
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.
Installation¶
via Anaconda channel roebel¶
Precompiled packages are available for Anaconda python3 under Linux (x86_64) and Mac OS X (> 10.9). For these systems you can install pysndfile simply by means of
conda install -c roebel pysndfile
Unfortunately, I don’t have a windows machine and therefore I cannot provide any packages for Windows.
compile with conda build recipe¶
You can use the conda recipe here. This build recipe wil automatically download and compile libsndfile building pysndfile.
via pypi¶
pip install pysndfile
should install pysndfile and python dependencies. Note, that pip cannot install libsndfile for you as it is not provided via pypi. To install libsndfile you should be able to use the software manager of your system. This will however only work if your software manager installs libsndfile such that the compiler used by the setup.py script will find it.
compile from sources¶
Note that for ompiling from sources you need to install requirements listed in requirements.txt file before starting the compilation. Moreover you need to install libsndfile as described in the previous section.
If the libsndfile (header and library) is not installed in the default compiler search path you have to specify the library and include directories to be added to this search paths. For this you can use either the command line options –sndfile-libdir and –sndfile-incdir that are available for the build_ext command or specify these two parameters in the setup.cfg file.
Windows¶
An experimental support for using pysndfile under windows has been added since version 1.3.4. For further comments see here as well as build scripts provided by sveinse. Note, that I do not have any windows machine and cannot provide any help in making this work.