Free Resampling Software

• Note: resample, libresample, and sndfile-resample (from libsamplerate) are already included in the Planet CCRMA Distribution. If you are running RedHat Linux, check out the Planet.
• resample-1.8.1.tar.gz (502 Kbytes) (v1.8.1 released November 11, 2006)
  The resample software package contains free sampling-rate conversion and filter design utilities written in C, including a stand-alone command-line sampling-rate conversion utility called resample. The package compiles readily under Linux and most other UNIX operating systems. It is released under the GNU Lesser General Public License (LGPL).
  • README file for resample software package
  • Older Version for NeXT Computers (49 Kbytes)
  • Original 1983+ source for the PDP KL-10 (Released under the Revised BSD License)

• libresample-0.1.3.tgz (LGPL) (released Jan, 7, 2004) by Dominic Mazzoni is a real-time library for sampling rate conversion providing several useful features relative to resample-1.7 on which it is based:
  • It should build ``out of the box'' on more platforms, including Linux, Solaris, and Mac OS X (using the included configure script). There is also a Visual C++ project file for building under Windows.
  • Input and output signals are in memory (as opposed to sound files).
  • Computations are in floating-point (instead of fixed-point).
  • Filter table increased by a factor of 32, yielding more accurate results, even without linear interpolation (which also makes it faster).
  • Data can be processed in small chunks, enabling time-varying resampling ratios (ideal for time-warping applications and supporting an ``external clock input'' in software).
  • Easily applied to any number of simultaneous data channels
  • README file for libresample-0.1.3

• Erik de Castro Lopo's libsamplerate
  • Same basic algorithm
  • Floating-point (resample is fixed-point--sometimes needed on DSP chips)
  • Configures for non-Linux platforms such as Mac OS X and Windows
  • Includes the command-line program sndfile-resample which works like resample
  • Uses Erik's libsndfile (resample uses Bill Schottstaedt's sndlib)
  • License is either GPL or commercial (resample is LGPL)

• The free Open Source Audio Library Project (OSALP) (LGPL) contains a C++ class based on resample.

• The Speex speech coder/decoder (based on CELP) contains a variation of the resample algorithm in the file resample.c, is free and open-source, and is released under a BSD-style license (i.e., free for both commercial and noncommercial uses). The code is characterized as ``working, but it's in a very early stage, so it may have artifacts ... the API isn't stable ...''. However, this appears to be the best BSD-licensed starting point.

• Paper on optimal FIR interpolation filter design: (.pdf) (.ps.gz)

To report bugs, or contribute enhancements, please send email to jos ( send email ).