Q is a cross-platform C++ library for Audio Digital Signal Processing. Aptly named after the "Q factor", a dimensionless parameter that describes the quality of a resonant circuit, the Q DSP Library is designed to be simple and elegant, as the simplicity of its name suggests, and efficient enough to run on small microcontrollers.
Q leverages the power of modern C++ and efficient use of functional programming techniques, especially function composition using fine-grained and reusable function objects (both stateless and stateful), to simplify complex DSP programming tasks without sacrificing readability.
Q is the host of some experimental Music related DSP facilities such as Virtual Pickups (Virtual pickup placement simulator) and Bitstream Autocorrelation (An extremely fast and efficient pitch detection scheme) the author has accumulated over the years as part of research and development, and will continue to evolve to accommodate more facilities necessary for the fulfillment of various Music related projects.
The library is Open Source and released under the very liberal MIT license.
An apology. I am an advocate of Open Source. But after having shared open-source projects for over 20 years now, starting with my contributions to the Boost libraries, it pains me to say that I am closing some source code for pragmatic concerns. The source code of technologies that are in very active research and development will be closed — that would be pitch detection and onset detection. If you are using the pitch detection source code now, I suggest forking the latest version with the current MIT license. I will close the pitch detection source code by mid-April.
Please follow this link for more info: Rethinking Open Source.
- 14 April 2021: Q v1.0 beta is released: https://github.com/cycfi/q/tree/v1.0_beta
- 11 March 2021: BACF pitch detection is going away. See announcement above.
- 4 February 2021: Posted Fast and Efficient Pitch Detection: Power of Two. Bitstream Autocorrelation (BACF) is fast and accurate. What can be better? Well, two BACFs in parallel!
- 6 July 2020: Posted Fast and Efficient Pitch Detection: Revisited. A long overdue article about the technical details of BACF.
- 25 June 2020: Pitch/period detection improvements now in master branch.
- 19 June 2020: Pitch/period detection improvements in develop branch (for now until it becomes stable). Mostly bug fixes; esp. the ability to handle higher frequencies and bigger low-high ranges.
- 18 May 2020: We're getting closer to a 1.0 release. Busy working on the docs, including small improvements on the example code.
Feel free to join the discord channel for discussion and chat with the developer.
Documentation is work in progress. Stay tuned...
Joel got into electronics and programming in the 80s because almost everything in music, his first love, is becoming electronic and digital. Since then, he builds his own guitars, effect boxes and synths. He enjoys playing distortion-laden rock guitar, composes and produces his own music in his home studio.
Joel de Guzman is the principal architect and engineer at Cycfi Research and a consultant at Ciere Consulting. He is a software engineer specializing in advanced C++ and an advocate of Open Source. He has authored a number of highly successful Open Source projects such as Boost.Spirit, Boost.Phoenix and Boost.Fusion. These libraries are all part of the Boost Libraries, a well respected, peer-reviewed, Open Source, collaborative development effort.
Copyright (c) 2014-2020 Joel de Guzman. All rights reserved. Distributed under the MIT License