Sema – Live Code Language Design Playground

Sema is a playground where you can rapidly prototype live coding mini-languages for signal synthesis, machine learning and machine listening.

Sema aims to provide an online integrated environment for designing both abstract high-level languages and more powerful low-level languages.

Sema implements a set of core design principles:

• Integrated signal engine – There is no conceptual split between the language and signal engine. Everything is a signal.

• Single sample signal processing – Per-sample sound processing for supporting techniques that use feedback loops, such as physical modelling, reverberation and IIR filtering.

• Sample rate transduction – It is simpler to do signal processing with one principal sample rate, the audio rate. Different sample rate requirements of dependent objects can be resolved by upsampling and downsampling, using a transducer. The transducer concept enables us to accommodate a variety of processes with varying sample rates (video, spectral rate, sensors, ML model inference) within a single engine.

• Minimal abstractions – There are no high-level abstractions such as buses, synths, nodes, servers, or any language scaffolding in our signal engine. Such abstractions sit within the end-user language design space.

Dependencies

Sema requires the following dependencies to be installed:

• Chrome browser or any Chromium-based browser (e.g. Brave, Microsoft Edge, Opera)
• Node.js version v11.10.0 or higher
• NPM cli OR Yarn

How to build and run the Sema playground on your machine

If you decide to use NPM, use:

$ cd sema
$ npm install
$ npm run build
$ npm run dev OR npm run serve 

If you decide to go with Yarn (our preferred package manager), to install it:

$ npm install -g yarn

To use Yarn:

$ cd sema
$ yarn
$ yarn build
$ yarn dev OR yarn serve 

Once you have the node application running, open Sema on your browser on the following ports

• yarn dev, go to http://localhost:8080 on your browser
• yarn serve, go to http://localhost:5001 on your browser

Linux Users

Sema uses Web Audio API Audio Worklets. Their performance seems very sensitive to CPU power scaling. If you are experiencing sound quality issues, try setting the CPU governor to performance mode. e.g on Ubuntu,

$ cpupower frequency-set --governor performance

Documentation

Default Livecoding Language

Sema Intermediate Language

Maximilian DSP API

Javascript Editor Utils

Publications

Bernardo, F., Kiefer, C., Magnusson, T. (forthcoming). A Signal Engine for a Live Code Language Ecosystem. Journal of Audio Engineering Society, Vol. 68, No. 1, October

Bernardo, F., Kiefer, C., Magnusson, T. (2020). Designing for a Pluralist and User-Friendly Live Code Language Ecosystem with Sema. 5th International Conference on Live Coding, University of Limerick, Limerick, Ireland

Bernardo, F., Kiefer, C., Magnusson, T. (2019). An AudioWorklet-based Signal Engine for a Live Coding Language Ecosystem. In Proceedings of Web Audio Conference 2019, Norwegian University of Science and Technology (NTNU), Trondheim, Norway (Best Paper Award at Web Audio Conference 2019)