SoundTouch audio processing library v2.3.1

SoundTouch library Copyright © Olli Parviainen 2001-2021

1. Introduction

SoundTouch is an open-source audio processing library that allows changing the sound tempo, pitch and playback rate parameters independently from each other, i.e.:

• Sound tempo can be increased or decreased while maintaining the original pitch
• Sound pitch can be increased or decreased while maintaining the original tempo
• Change playback rate that affects both tempo and pitch at the same time
• Choose any combination of tempo/pitch/rate

1.1 Contact information

Author email: oparviai 'at' iki.fi

SoundTouch WWW page: http://soundtouch.surina.net

SoundTouch git repository: https://gitlab.com/soundtouch/soundtouch.git

2. Compiling SoundTouch

Before compiling, notice that you can choose the sample data format if it's desirable to use 16bit integer sample data instead of floating point samples. See section "sample data format" for more information.

Also notice that SoundTouch can use OpenMP instructions for parallel computation to accelerate the runtime processing speed in multi-core systems, however, these improvements need to be separately enabled before compiling. See OpenMP notes in Chapter 3 below.

2.1. Building in Microsoft Windows

Project files for Microsoft Visual C++ are supplied with the source code package. Go to Microsoft WWW page to download Microsoft Visual Studio Express version for free.

To build the binaries with Visual C++ compiler, either run "make-win.bat" script, or open the appropriate project files in source code directories with Visual Studio. The final executable will appear under the "SoundTouch\bin" directory. If using the Visual Studio IDE instead of the make-win.bat script, directories bin and lib may need to be created manually to the SoundTouch package root for the final executables. The make-win.bat script creates these directories automatically.

C# example: The source code package includes also a C# example application for Windows that shows how to invoke SoundTouch.dll dynamic-load library for processing mp3 audio.

OpenMP NOTE: If activating the OpenMP parallel computing in the compilation, the target program will require additional vcomp dll library to properly run. In Visual C++ 9.0 these libraries can be found in the following folders.

• x86 32bit: C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\redist\x86\Microsoft.VC90.OPENMP\vcomp90.dll
• x64 64bit: C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\redist\amd64\Microsoft.VC90.OPENMP\vcomp90.dll

In other VC++ versions the required library will be expectedly found in similar "redist" location.

Notice that as minor demonstration of a "dll hell" phenomenon both the 32-bit and 64-bit version of vcomp90.dll have the same filename but different contents, thus choose the proper version to allow the program to start.

2.2. Building in Gnu platforms

The SoundTouch library compiles in practically any platform supporting GNU compiler (GCC) tools.

2.2.1 Compiling with autotools

To install build prerequisites for 'autotools' tool chain:

    sudo apt-get install automake autoconf libtool build-essential

To build and install the binaries, run the following commands in /soundtouch directory:

./bootstrap  -

./configure  -

make         -

make install -

The GNU autotools compilation does not automatically create a shared-library version of SoundTouch (.so or .dll) that features position-independent code and C-language api that are more suitable for cross-language development than C++ libraries.

Use script "make-gnu-dll-sh" to build a portable dynamic library version if such is desired.

2.2.2 Compiling with cmake

'cmake' build scripts are provided as an alternative to the autotools toolchain.

To install cmake build prerequisites:

    sudo apt-get install libtool build-essential cmake

To build:

    cmake .
    make -j
    make install

To compile the additional portable Shared Library / DLL version with the native C-language API:

    cmake . -DSOUNDTOUCH_DLL=ON
    make -j
    make install

2.3. Building in Android

Android compilation instructions are within the source code package, see file "source/Android-lib/README-SoundTouch-Android.html" in the source code package.

The Android compilation automatically builds separate .so library binaries for ARM, X86 and MIPS processor architectures. For optimal device support, include all these .so library binaries into the Android .apk application package, so the target Android device can automatically choose the proper library binary version to use.

The source/Android-lib folder includes also an Android example application that processes WAV audio files using SoundTouch library in Android devices.

2.4. Building in Mac

Install autoconf tool as instructed in http://macappstore.org/autoconf/, or alternatively the 'cmake' toolchain.

Then, build as described above in section "Building in Gnu platforms".

3. About implementation & Usage tips

3.1. Supported sample data formats

The sample data format can be chosen between 16bit signed integer and 32bit floating point values.

In Windows environment, the sample data format is chosen in file "STTypes.h" by choosing one of the following defines:

• #define SOUNDTOUCH_INTEGER_SAMPLES for 16bit signed integer
• #define SOUNDTOUCH_FLOAT_SAMPLES for 32bit floating point

In GNU environment, the floating sample format is used by default, but integer sample format can be chosen by giving the following switch to the configure script:

./configure --enable-integer-samples

The sample data can have either single (mono) or double (stereo) audio channel. Stereo data is interleaved so that every other data value is for left channel and every second for right channel. Notice that while it'd be possible in theory to process stereo sound as two separate mono channels, this isn't recommended because processing the channels separately would result in losing the phase coherency between the channels, which consequently would ruin the stereo effect.

Sample rates between 8000-48000H are supported.

3.2. Processing latency

The processing and latency constraints of the SoundTouch library are:

• Input/output processing latency for the SoundTouch processor is around 100 ms. This is when time-stretching is used. If the rate transposing effect alone is used, the latency requirement is much shorter, see section 'About algorithms'.
• Processing CD-quality sound (16bit stereo sound with 44100H sample rate) in real-time or faster is possible starting from processors equivalent to Intel Pentium 133Mh or better, if using the "quick" processing algorithm. If not using the "quick" mode or if floating point sample data are being used, several times more CPU power is typically required.

3.3. About algorithms

SoundTouch provides three seemingly independent effects: tempo, pitch and playback rate control. These three controls are implemented as combination of two primary effects, sample rate transposing and time-stretching.

Sample rate transposing affects both the audio stream duration and pitch. It's implemented simply by converting the original audio sample stream to the desired duration by interpolating from the original audio samples. In SoundTouch, linear interpolation with anti-alias filtering is used. Theoretically a higher-order interpolation provide better result than 1st order linear interpolation, but in audio application linear interpolation together with anti-alias filtering performs subjectively about as well as higher-order filtering would.

Time-stretching means changing the audio stream duration without affecting it's pitch. SoundTouch uses WSOLA-like time-stretching routines that operate in the time domain. Compared to sample rate transposing, time-stretching is a much heavier operation and also requires a longer processing "window" of sound samples used by the processing algorithm, thus increasing the algorithm input/output latency. Typical i/o latency for the SoundTouch time-stretch algorithm is around 100 ms.

Sample rate transposing and time-stretching are then used together to produce the tempo, pitch and rate controls:

• 'Tempo' control is implemented purely by time-stretching.
• 'Rate' control is implemented purely by sample rate transposing.
• 'Pitch' control is implemented as a combination of time-stretching and sample rate transposing. For example, to increase pitch the audio stream is first time-stretched to longer duration (without affecting pitch) and then transposed back to original duration by sample rate transposing, which simultaneously reduces duration and increases pitch. The result is original duration but increased pitch.

3.4 Tuning the algorithm parameters

The time-stretch algorithm has few parameters that can be tuned to optimize sound quality for certain application. The current default parameters have been chosen by iterative if-then analysis (read: "trial and error") to obtain best subjective sound quality in pop/rock music processing, but in applications processing different kind of sound the default parameter set may result into a sub-optimal result.

The time-stretch algorithm default parameter values are set by the following #defines in file "TDStretch.h":

#define DEFAULT_SEQUENCE_MS     AUTOMATIC
#define DEFAULT_SEEKWINDOW_MS   AUTOMATIC
#define DEFAULT_OVERLAP_MS      8

These parameters affect to the time-stretch algorithm as follows:

• DEFAULT_SEQUENCE_MS: This is the default length of a single processing sequence in milliseconds which determines the how the original sound is chopped in the time-stretch algorithm. Larger values mean fewer sequences are used in processing. In principle a larger value sounds better when slowing down the tempo, but worse when increasing the tempo and vice versa.
  
  By default, this setting value is calculated automatically according to tempo value.
  
• DEFAULT_SEEKWINDOW_MS: The seeking window default length in milliseconds is for the algorithm that seeks the best possible overlapping location. This determines from how wide a sample "window" the algorithm can use to find an optimal mixing location when the sound sequences are to be linked back together.
  
  The bigger this window setting is, the higher the possibility to find a better mixing position becomes, but at the same time large values may cause a "drifting" sound artifact because neighboring sequences can be chosen at more uneven intervals. If there's a disturbing artifact that sounds as if a constant frequency was drifting around, try reducing this setting.
  
  By default, this setting value is calculated automatically according to tempo value.
  
• DEFAULT_OVERLAP_MS: Overlap length in milliseconds. When the sound sequences are mixed back together to form again a continuous sound stream, this parameter defines how much the ends of the consecutive sequences will overlap with each other.
  
  This shouldn't be that critical parameter. If you reduce the DEFAULT_SEQUENCE_MS setting by a large amount, you might wish to try a smaller value on this.

Notice that these parameters can also be set during execution time with functions "TDStretch::setParameters()" and "SoundTouch::setSetting()".

The table below summaries how the parameters can be adjusted for different applications:

SEQUENCE_MS

SEEKWINDOW_MS

OVERLAP_MS

3.5 Performance Optimizations

Integer vs floating point:

Floating point sample type is generally recommended because it provides better sound quality.

However, execution speed difference between integer and floating point processing depends on the CPU architecture. As rule of thumb,

• in 32-bit x86 floating point and integer are roughly equally fast
• in 64-bit x86/x64 floating point can be significantly faster than integer version, because MMX integer optimizations are not available in the x64 architecture. That depends on the compiler however, so that gcc can autovectorize integer routines to work equally fast as floating point, where as Visual C++ (2017) does not perform equally well and produces integer code that runs some 3x slower than SSE-optimized floating poing code.
• in ARMv7 integer routines are twice as fast as floating point. Their relative difference is roughly the same both with and without NEON; NEON vfpu can however bring 2.4x speed improvement.
• in other platforms: try out if the execution time performance makes a big difference

General optimizations:

The time-stretch routine has a 'quick' mode that substantially speeds up the algorithm but may slightly compromise the sound quality. This mode is activated by calling SoundTouch::setSetting() function with parameter id of SETTING_USE_QUICKSEEK and value "1", i.e.

setSetting(SETTING_USE_QUICKSEEK, 1);

CPU-specific optimizations:

Intel x86 specific SIMD optimizations are implemented using compiler intrinsics, providing about a 3x processing speedup for x86 compatible processors vs. non-SIMD implementation:

• MMX optimized routines are used in 32-bit x86 build when 16bit integer sample type is used
• SSE optimized routines are used in 32- and 64-bit x86 CPUs when 32bit floating point sample type is used

The algorithms are tuned to utilize autovectorization efficiently also in other CPU architectures, for example ARM cpus see approx 2.4x processing speedup when NEON SIMD support is present.

3.5 OpenMP parallel computation

SoundTouch 1.9 onwards support running the algorithms parallel in several CPU cores. Based on benchmark the experienced multi-core processing speed-up gain ranges between +30% (on a high-spec dual-core x86 Windows PC) to 215% (on a moderately low-spec quad-core ARM of Raspberry Pi2).

See an external blog article with more detailed discussion about the SoundTouch OpenMP optimization.

The parallel computing support is implemented using OpenMP spec 3.0 instructions. These instructions are supported by Visual C++ 2008 and later, and GCC v4.2 and later. Compilers that do not supporting OpenMP will ignore these optimizations and routines will still work properly. Possible warnings about unknown #pragmas are related to OpenMP support and can be safely ignored.

The OpenMP improvements are disabled by default, and need to be enabled by developer during compile-time. Reason for this is that parallel processing adds moderate runtime overhead in managing the multi-threading, so it may not be necessary nor desirable in all applications. For example real-time processing that is not constrained by CPU power will not benefit of speed-up provided by the parallel processing, in the contrary it may increase power consumption due to the increased overhead.

However, applications that run on low-spec multi-core CPUs and may otherwise have possibly constrained performance will benefit of the OpenMP improvements. This include for example multi-core embedded devices.

OpenMP parallel computation can be enabled before compiling SoundTouch library as follows:

• Visual Studio: Open properties for the SoundTouch sub-project, browse to C/C++ and Language settings. Set there "OpenMP support" to "Yes". Alternatively add /openmp switch to command-line parameters
• GNU: Run the configure script with "./configure --enable-openmp" switch, then run make as usually
• Android: Add "-fopenmp" switches to compiler & linker options, see README-SoundTouch-Android.html in the source code package for more detailed instructions.

4. SoundStretch audio processing utility

SoundStretch audio processing utility
Copyright (c) Olli Parviainen 2002-2015

SoundStretch is a simple command-line application that can change tempo, pitch and playback rates of WAV sound files. This program is intended primarily to demonstrate how the "SoundTouch" library can be used to process sound in your own program, but it can as well be used for processing sound files.

4.1. SoundStretch Usage Instructions

SoundStretch Usage syntax:

soundstretch infilename outfilename [switches]

Where:

"infilename"

"outfilename"

[switches]

Available control switches are:

-tempo=n 

-pitch=n

-rate=n

-bpm=n

-quick

-naa

-license

Notes:

• To use standard input/output pipes for processing, give "stdin" and "stdout" as input/output filenames correspondingly. The standard input/output pipes will still carry the audio data in .wav audio file format.
• The numerical switches allow both integer (e.g. "-tempo=123") and decimal (e.g. "-tempo=123.45") numbers.
• The "-naa" and/or "-quick" switches can be used to reduce CPU usage while compromising some sound quality
• The BPM detection algorithm works by detecting repeating bass or drum patterns at low frequencies of <250Hz. A lower-than-expected BPM figure may be reported for music with uneven or complex bass patterns.

4.2. SoundStretch usage examples

Example 1

The following command increases tempo of the sound file "originalfile.wav" by 12.5% and stores result to file "destinationfile.wav":

soundstretch originalfile.wav destinationfile.wav -tempo=12.5

Example 2

The following command decreases the sound pitch (key) of the sound file "orig.wav" by two semitones and stores the result to file "dest.wav":

soundstretch orig.wav dest.wav -pitch=-2

Example 3

The following command processes the file "orig.wav" by decreasing the sound tempo by 25.3% and increasing the sound pitch (key) by 1.5 semitones. Resulting .wav audio data is directed to standard output pipe:

soundstretch orig.wav stdout -tempo=-25.3 -pitch=1.5

Example 4

The following command detects the BPM rate of the file "orig.wav" and adjusts the tempo to match 100 beats per minute. Result is stored to file "dest.wav":

soundstretch orig.wav dest.wav -bpm=100

Example 5

The following command reads .wav sound data from standard input pipe and estimates the BPM rate:

soundstretch stdin -bpm

Example 6

The following command tunes song from original 440Hz tuning to 432Hz tuning: this corresponds to lowering the pitch by -0.318 semitones:

soundstretch original.wav output.wav -pitch=-0.318

5. Change History

5.1. SoundTouch library Change History

2.3.1:

• Adjusted cmake build settings and header files that cmake installs

2.3.0:

• Disable setting "SOUNDTOUCH_ALLOW_NONEXACT_SIMD_OPTIMIZATION" by default. The original purpose of this setting was to avoid performance penalty due to unaligned SIMD memory accesses in old CPUs, but that is not any more issue in concurrent CPU SIMD implementations and having this setting enabled can cause slight compromise in result quality.
• Bugfix: soundtouch.clear() to really clear whole processing pipeline state. Earlier individual variables were left uncleared, which caused slightly different result if the same audio stream were processed again after calling clear().
• Bugfix: TDstretch to align initial offset position to be in middle of correlation search window. This ensures that with zero tempo change the output will be same as input.
• Bugfix: Fix a bug in TDstrectch with too small initial skipFract value that occurred with certain processing parameter settings: Replace assert with assignment that corrects the situation.
• Remove OpenMP "_init_threading" workaround from Android build as it's not needed with concurrent Android SDKs any more.

2.2:

• Improved source codes so that compiler can autovectorize them more effectively. This brings remarkable improvement e.g. ARM cpus equipped with NEON vfpu: Bencmarked 2.4x improvement in execution speed in ARMv7l vs the previous SoundTouch version for both integer and floating point sample types.
• Bugfix: Resolved bad sound quality when using integer sample types in non-x86 CPU
• Bugfix: Fixed possible reading past end of array in BPM peak detection algorithm

2.1.2:

• Bump version to 2.1.2 also in configure.ac. The earlier release had old version info for GNU autotools.

2.1.1:

• Bugfixes: Fixed potential buffer overwrite bugs in WavFile routines. Replaced asserts with runtime exceptions.
• Android: Migrated the SoundTouch Android example to new Android Studio
• Automake: unset ACLOCAL in bootstrap script in case earlier build script has set it

2.1:

• Refactored C# interface example
• Disable anti-alias filter when switch SOUNDTOUCH_PREVENT_CLICK_AT_RATE_CROSSOVER defined because anti-alias filter cause slight click if the rate change crosses zero during processing
• Added script for building SoundTouchDll dynamic-link-library for GNU platforms
• Rewrote Beats-per-Minute analysis algorithm for more reliable BPM detection
• Added BPM functions to SoundTouchDll API
• Migrated Visual Studio project files to MSVC 201x format
• Replaced function parameter value asserts with runtime exceptions
• Code maintenance & style cleanup

2.0:

• Added functions to get initial processing latency, duration ratio between the original input and processed output tracks, and clarified reporting of input/output batch sizes
• Fixed issue that added brief sequence of silence to beginning of output audio
• Adjusted algorithm parameters to reduce reverberating effect at tempo slowdown
• Bugfix: Fixed a glitch that could cause negative array indexing in quick seek algorithm
• Bugfix: flush() didn't properly flush final samples from the pipeline on 2nd time in case that soundtouch object instance was recycled and used for processing a second audio stream.
• Bugfix: Pi value had incorrect 9th/10th decimals
• Added C# example application that uses SoundTouch dll library for processing MP3 files

1.9.2:

• Fix in GNU package configuration

1.9.1:

• Improved SoundTouch::flush() function so that it returns precisely the desired amount of samples for exact output duration control
• Redesigned quickseek algorithm for improved sound quality when using the quickseek mode. The new quickseek algorithm can find 99% as good results as the default full-scan mode, while the quickseek algorithm is remarkable less CPU intensive.
• Added adaptive integer divider scaling for improved sound quality when using integer processing algorithm

1.9:

• Added support for parallel computation support via OpenMP primitives for better performance in multicore systems. Benchmarks show that achieved parallel processing speedup improvement typically range from +30% (x86 dual-core) to +180% (ARM quad-core). The OpenMP optimizations are disabled by default, see OpenMP notes above in this readme file how to enabled these optimizations.
• Android: Added support for Android devices featuring X86 and MIPS CPUs, in addition to ARM CPUs.
• Android: More versatile Android example application that processes WAV audio files with SoundTouch library
• Replaced Windows-like 'BOOL' types with native 'bool'
• Changed documentation token to "dist_doc_DATA" in Makefile.am file
• Miscellaneous small fixes and improvements

1.8.0:

• Added support for multi-channel audio processing
• Added support for cubic and shannon interpolation for rate and pitch shift effects besides the original linear interpolation, to reduce aliasing at high frequencies due to interpolation. Cubic interpolation is used as default for floating point processing, and linear interpolation for integer processing.
• Fixed bug in anti-alias filtering that limited stop-band attenuation to -10 dB instead of <-50dB, and increased filter length from 32 to 64 taps to further reduce aliasing due to frequency folding.
• Performance improvements in cross-correlation algorithm
• Other bug and compatibility fixes

1.7.1:

• Added files for Android compilation

1.7.0:

• Sound quality improvements/li>
• Improved flush() to adjust output sound stream duration to match better with ideal duration
• Rewrote x86 cpu feature check to resolve compatibility problems
• Configure script automatically checks if CPU supports mmx & sse compatibility for GNU platform, and the script support now "--enable-x86-optimizations" switch to allow disabling x86-specific optimizations.
• Revised #define conditions for 32bit/64bit compatibility
• gnu autoconf/automake script compatibility fixes
• Tuned beat-per-minute detection algorithm

1.6.0:

• Added automatic cutoff threshold adaptation to beat detection routine to better adapt BPM calculation to different types of music
• Retired 3DNow! optimization support as 3DNow! is nowadays obsoleted and assembler code is nuisance to maintain
• Retired "configure" file from source code package due to autoconf/automake versio conflicts, so that it is from now on to be generated by invoking "boostrap" script that uses locally available toolchain version for generating the "configure" file
• Resolved namespace/label naming conflicts with other libraries by replacing global labels such as INTEGER_SAMPLES with more specific SOUNDTOUCH_INTEGER_SAMPLES etc.
  
• Updated windows build scripts & project files for Visual Studio 2008 support
• Updated SoundTouch.dll API for .NET compatibility
• Added API for querying nominal processing input & output sample batch sizes

1.5.0:

• Added normalization to correlation calculation and improvement automatic seek/sequence parameter calculation to improve sound quality
• Bugfixes:
  • Fixed negative array indexing in quick seek algorithm
  • FIR autoalias filter running too far in processing buffer
  • Check against zero sample count in rate transposing
  • Fix for x86-64 support: Removed pop/push instructions from the cpu detection algorithm.
  • Check against empty buffers in FIFOSampleBuffer
  • Other minor fixes & code cleanup
• Fixes in compilation scripts for non-Intel platforms
• Added Dynamic-Link-Library (DLL) version of SoundTouch library build, provided with Delphi/Pascal wrapper for calling the dll routines
• Added #define PREVENT_CLICK_AT_RATE_CROSSOVER that prevents a click artifact when crossing the nominal pitch from either positive to negative side or vice versa

1.4.1:

• Fixed a buffer overflow bug in BPM detect algorithm routines if processing more than 2048 samples at one call

1.4.0:

• Improved sound quality by automatic calculation of time stretch algorithm processing parameters according to tempo setting
• Moved BPM detection routines from SoundStretch application into SoundTouch library
• Bugfixes: Usage of uninitialied variables, GNU build scripts, compiler errors due to 'const' keyword mismatch.
• Source code cleanup

1.3.1:

• Changed static class declaration to GCC 4.x compiler compatible syntax.
• Enabled MMX/SSE-optimized routines also for GCC compilers. Earlier the MMX/SSE-optimized routines were written in compiler-specific inline assembler, now these routines are migrated to use compiler intrinsic syntax which allows compiling the same MMX/SSE-optimized source code with both Visual C++ and GCC compilers.
• Set floating point as the default sample format and added switch to the GNU configure script for selecting the other sample format.

1.3.0:

• Fixed tempo routine output duration inaccuracy due to rounding error
• Implemented separate processing routines for integer and floating arithmetic to allow improvements to floating point routines (earlier used algorithms mostly optimized for integer arithmetic also for floating point samples)
• Fixed a bug that distorts sound if sample rate changes during the sound stream
• Fixed a memory leak that appeared in MMX/SSE/3DNow! optimized routines
• Reduced redundant code pieces in MMX/SSE/3DNow! optimized routines vs. the standard C routines.
• MMX routine incompatibility with new gcc compiler versions
• Other miscellaneous bug fixes

1.2.1:

• Added automake/autoconf scripts for GNU platforms (in courtesy of David Durham)
• Fixed SCALE overflow bug in rate transposer routine.
• Fixed 64bit address space bugs.
• Created a 'soundtouch' namespace for SAMPLETYPE definitions.

1.2.0:

• Added support for 32bit floating point sample data type with SSE/3DNow! optimizations for Win32 platform (SSE/3DNow! optimizations currently not supported in GCC environment)
• Replaced 'make-gcc' script for GNU environment by master Makefile
• Added time-stretch routine configurability to SoundTouch main class
• Bugfixes

1.1.1:

• Moved SoundTouch under lesser GPL license (LGPL). This allows using SoundTouch library in programs that aren't released under GPL license.
• Changed MMX routine organiation so that MMX optimized routines are now implemented in classes that are derived from the basic classes having the standard non-mmx routines.
• MMX routines to support gcc version 3.
• Replaced windows makefiles by script using the .dsw files

1.0.1:

• "mmx_gcc.cpp": Added "using namespace std" and removed "return 0" from a function with void return value to fix compiler errors when compiling the library in Solaris environment.
• Moved file "FIFOSampleBuffer.h" to "include" directory to allow accessing the FIFOSampleBuffer class from external files.

1.0:

• Initial release

5.2. SoundStretch application Change History

1.9:

• Added support for WAV file 'fact' information chunk.

1.7.0:

• Bugfixes in Wavfile: exception string formatting, avoid getLengthMs() integer precision overflow, support WAV files using 24/32bit sample format.

1.5.0:

• Added "-speech" switch to activate algorithm parameters more suitable for speech processing than the default parameters tuned for music processing.

1.4.0:

• Moved BPM detection routines from SoundStretch application into SoundTouch library
• Allow using standard input/output pipes as audio processing input/output streams

1.3.0:

• Simplified accessing WAV files with floating point sample format.

1.2.1:

• Fixed 64bit address space bugs.

1.2.0:

• Added support for 32bit floating point sample data type
• Restructured the BPM routines into separate library
• Fixed big-endian conversion bugs in WAV file routines (hopefully :)

1.1.1:

• Fixed bugs in WAV file reading & added byte-order conversion for big-endian processors.
• Moved SoundStretch source code under 'example' directory to highlight difference from SoundTouch stuff.
• Replaced windows makefiles by script using the .dsw files
• Output file name isn't required if output isn't desired (e.g. if using the switch '-bpm' in plain format only)

1.1:

• Fixed "Release" settings in Microsoft Visual C++ project file (.dsp)
• Added beats-per-minute (BPM) detection routine and command-line switch "-bpm"

1.01:

• Initial release

6. Acknowledgements

Kudos for these people who have contributed to development or submitted bugfixes:

• Arthur A
• Paul Adenot
• Richard Ash
• Stanislav Brabec
• Christian Budde
• Jamie Bullock
• Chris Bryan
• Jacek Caban
• Marketa Calabkova
• Brian Cameron
• Jason Champion
• Giuseppe Cigala
• David Clark
• Patrick Colis
• Miquel Colon
• Jim Credland
• Sandro Cumerlato
• Gerry Fan
• Justin Frankel
• Masa H.
• Jason Garland
• Takashi Iwai
• Thomas Klausner
• Lu Zhihe
• Luzpaz
• Tony Mechelynck
• Mathias Möhl
• Yuval Naveh
• Mats Palmgren
• Chandni Patel
• Paulo Pizarro
• Andrey Ponomarenko
• Blaise Potard
• Michael Pruett
• Rajeev Puran
• RJ Ryan
• John Sheehy
• Tim Shuttleworth
• Albert Sirvent
• Tyson Smith
• John Stumpo
• Mario di Vece
• Rémi Verschelde
• Katja Vetter
• Wu Q.

Moral greetings to all other contributors and users also!

7. LICENSE

SoundTouch audio processing library
Copyright (c) Olli Parviainen

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License version 2.1 as published by the Free Software Foundation.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

---

commercial license alternative also available, contact author for details.