libspecbleach

C library for audio noise reduction and other spectral effects

Table of Contents

• Background
• De-noise Algorithms
• Build
• Installation
• Usage Examples
• Development
• Contributing
• License

Background

This library is based on the algorithms that were used in noise-repellent. These were extracted into a standalone library to remove the lv2 dependency. It was designed to be extensible and modular. It uses the concept of a spectral processor which itself uses a short time Fourier transform (STFT) to process the audio. There are two initial processors in place, one which uses the adaptive part of noise repellent and one that uses the manual capturing profile based denoising. The library could be extended with more spectral processors using any STFT-based algorithm such as de-crackle, de-click and other audio restoration algorithms.

De-noise Algorithms

There are several techniques implemented in the library that are being used in the denoisers, such as masking thresholds estimation, onset detectors, etc. All these are being used in conjunction to improve the very basic spectral subtraction algorithm. Most of the papers used are listed in the wiki of the project. Also a block diagram is provided to explain the reduction architecture.

Build

If you wish to compile yourself and install the library you will need:

• A C compiling toolchain (GCC or Clang)
• Meson build system (0.60.0 or newer)
• Ninja build tool
• FFTW3 library (float version)
• libsndfile (optional, for examples)

Installation

git clone https://github.com/lucianodato/libspecbleach.git
cd libspecbleach
meson setup build --buildtype=release
meson compile -C build
sudo meson install -C build

Build Options

You can configure the build using -Doption=value:

• enable_examples: Build example applications (default: false). Requires libsndfile.
• enable_tests: Build unit and integration tests (default: false). Requires libsndfile.
• static_deps: Link internal dependencies (like FFTW3) statically (default: false). Useful for creating self-contained libraries.
• custom_warning_level: 0-3 (default: 2). Controls compiler warning verbosity.
• treat_warnings_as_errors: Treat compiler warnings as errors (default: false).
• enable_sanitizers: Enable sanitizers in debug builds (default: false).
• sanitize_address: Enable AddressSanitizer (default: false).
• sanitize_undefined: Enable UndefinedBehaviorSanitizer (default: false).

Example for a static build with examples:

meson setup build -Dstatic_deps=true -Denable_examples=true
meson compile -C build

Usage Examples

Simple console apps examples are provided to demonstrate how to use the library. It needs libsndfile to compile successfully. You can build them with:

meson setup build --buildtype=release -Denable_examples=true
meson compile -C build

Adaptive noise reduction

./build/example/adenoiser_demo <input file name> <output file name>

Manual noise reduction

./build/example/denoiser_demo <input file name> <output file name>

It will recognize any libsndfile supported format.

Development

Building for Development

For development builds with debugging symbols:

meson setup build --buildtype=debug
meson compile -C build

Code Formatting

The project uses clang-format for code formatting. To format the code:

meson compile format -C build

Running Tests

If tests are enabled:

meson setup build -Denable_tests=true
meson test -C build

Coverage

To generate coverage reports locally, you will need gcovr or lcov installed.

meson setup build --buildtype=debug -Db_coverage=true
meson compile -C build
meson test -C build
ninja -C build coverage-html

The report will be available in build/meson-logs/coveragereport/index.html.

License

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

See LICENSE for more details.