Research and development

Generalized Moog Ladder Filter: Part I & Part II

S. D'Angelo and V. Välimäki, IEEE/ACM Trans. Audio, Speech, and Lang. Process., vol. 22, no. 12, December 2014.

The ladder filter is generalized to any number of stages and its linear response is analysed in depth. A low cost linear digital model that correctly reproduces the frequency response is proposed.

Then a new ZDF technique is introduced that is fully non-iterative, perfectly accounts for linear behavior, requires minimal topology modifications and no transformation of nonlinearities, leading to a lightweight, accurate, and stable large-signal model of the generalized device.

Fast Approximation of the Lambert W Function for Virtual Analog Modelling

S. D'Angelo, L. Gabrielli, and L. Turchet, in Proc. 22^nd Intl. Conf. Digital Audio Effects (DAFx-19), Birmingham, UK, September 2019.

The paper suggests reformulating expressions containing the Lambert W function in terms of the Wright Omega function and provides very fast approximations.

Two application examples show the usefulness of the proposed method.

Arbitrary-Order IIR Antiderivative Antialiasing

P. P. La Pastina, S. D'Angelo, and L. Gabrielli, in Proc. 24^th Intl. Conf. Digital Audio Effects (DAFx20in21), pp. 9–16, Vienna, Austria, September 2021.

Antiderivative antialiasing is extended to use arbitrary IIR filters for the virtual downsampling by employing partial fraction expansion and analytical or numerical integration.

Formulas are given for single and multiple, real and complex conjugate poles.

Brickworks and Brickworks Pro

Brickworks is a foundational audio DSP toolkit providing over 50 core algorithms for building audio engines across platforms. It is suitable for equalizers, compressors, multi-effects, and synthesizers, and is available under GPLv3 or a proprietary license.

Brickworks Pro is an expanding collection of advanced DSP algorithms designed for high-end and demanding applications, offering improved sound quality and control in critical parts of an audio engine. Algorithms are licensed individually under a liberal proprietary license.

Ciaramella

Ciaramella is an experimental, minimalistic, declarative, modular language for audio DSP based on the synchronous data flow computational model. It is particularly well-suited for implementing highly-coupled DSP algorithms such as wave digital filters and state-space systems.

Its compiler, implemented in JavaScript and released under an ISC-style license, translates Ciaramella programs to C/C++, JavaScript, and MATLAB.