libinterp

A library for real-time data interpolation

About

libinterp is a tiny library for real-time data interpolation, especially focused on sound resampling.

It is written in plain C and, as of now, it just offers three algorithms (zero order hold, linear and cubic splines calculated on 4 points), only on mono channels and only using regular float values for input and output.

However, you can already process multiple mono channels and switch algorithms and buffer sizes (thus also the output rate) on the fly.

For the (near or far) future I hope to add some sinc-based algorithms, (optional?) low-pass filtering when downsampling, optional limiting (maybe normalization?), support for other data encodings, maybe even support for interleaved data for multiple channels and some toy/simple analysis/example programs.

However this is a "part part time" thing, so I'm not working regularly on it. Contributions are very welcome. ;-)

News

2007-12-05: First public release: libinterp 0.1.0.

License

This software is licensed under a MIT-style license. Here's a copy:

Copyright (c) 2007, Stefano D'Angelo  <zanga.mail@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

Download

You can get it here.

Installation

As usual:

$ ./configure
$ make
# make install

(./configure --help for configuration options).

Usage

An example (you can always do more complex things, obviously):

#include <libinterp/libinterp.h>

[...]

float in_buf[], out_buf[];
unsigned int in_samples, out_samples;
float last_in_samples[4] = {0.0, 0.0, 0.0, 0.0};

[...]

while (have_some_data_to_process)
	interp_spline(in_buf, in_samples, out_buf, out_samples, last_in_samples);

[...]

You can issue a make doxygen-doc to generate Doxygen documentation from the public headers (you have to install those files manually, though). The generated API reference should, then, be found in the doc/reference directory.

Porting

As of now it works on Linux and BeOS (probably Haiku and Zeta too).

However, since the code is very platform neutral, you can easily port it to other operating systems as well. If you're interested, take a look at the configure.ac and include/libinterp/config.h files (those should be quite self-explaining).

Contacts

For anything: zanga _dot_ mail _at_ gmail _dot_ com.