frantic0 / sema-engine-rollup

Demonstrator of the sema-engine library with a Rollup bundler setup

sema-engine-rollup

sema-engine-rollup contains an example of how to create an application with the sema-engine library and the Rollup bundler. This includes importing the sema-engine module from node_modules and using it as an ES module, and emitting its dependencies.

sema-engine provides a high-performance audio engine for modern Web applications, with an easy-to-use API. It was extracted from sema, an app developed with @chriskiefer and @thormagnusson, and refactored for project MIMIC.

sema-engine builds upon the following components:

• the Maximilian DSP C++ library – from which sema-engine consumes DSP objects, as a git submodule

• the Web Audio API Audio Worklet – packs a bespoke Audio Worklet node (src/engine.js) and processor (maxi-processor), which loads Maximilian DSP objects and dynamic program specifications

• the Nearley compiler – generates parsers from an EBNF grammar specification

The sema-engine library also exposes UMD modules (works on the browser, with modern native JS modules and older JS module formats—amd, cjs for nodejs applications—think electron!).

rollup-sema-engine uses Github Actions workflows for build automation and continuous integration. The development builds propagate source maps (.map files)—so you can have modern debugging features like using breakpoints in the context of the client application. The production build ships all formats optimised and minified.

Usage

To build the library and the app, run:

npm run build

To run the app on http://localhost:5000, run:

npm run dev

For an advanced use, check how sema-engine is integrated in Sema, a full-fledged application from which sema-engine was extracted.

You can use also use the sema-engine library modules in an a HTML file using inline <script> tags (check the published example which is output by the development build).

<script type="module">

    import {
      Engine,
      compile,
      Learner,
      getBlock
    } from "./sema-engine.mjs";

</script>

Note the that the script tag for the main module sema-engine.mjs has type = module.

When initialising sema-engine, you need to pass the audioWorkletURL URL which points to where package dependencies – e.g. maxi-processor.js and maximilian.wasmmodule.js (check the dist/ folder) – should be served from.

  let engine,
      analyser = 0,
      compiledParser = {},
      grammarCompilationErrors = "",
      livecodeParseErrors,
      livecodeParseTree,
      dspCode,
      learner
      ;

  const $ = (elemId, callback) =>
    document.getElementById(elemId).addEventListener("click", callback);

  $("playButton", "click", () => {
    const audioWorkletURL = origin + "/maxi-processor.js";
    engine = new Engine();
    engine.init("maxi-processor", audioWorkletURL);
    engine.play();
  })

  $("stopButton", () => engine.stop());
  $("plusButton", () => engine.more());
  $("minusButton", () => engine.less());

  $("loadSamplesButton", () => {
    engine.loadSample("crebit2.ogg", "./audio/crebit2.ogg");
    engine.loadSample("kick1.wav", "./audio/kick1.wav");
    engine.loadSample("snare1.wav", "./audio/snare1.wav");
  });

  $("learnerButton", "click", async () => {
    learner = new Learner();
    if(engine){
      engine.addEventListener('onSharedBuffer', e => learner.createSharedBuffer(e) ); // Engine's SAB emissions subscribed by Learner
      learner.addEventListener('onSharedBuffer', e => engine.pushSharedBuffer(e) );  // Learner's SAB emissions subscribed by Engine
    }
    await learner.init(document.location.origin); // when Learner initializes
  });
</script>

To compile the livecode, you need to do it against its grammar language specification, with the compile function. Only then you can inject the resulting code in the engine and evaluate it.

For the JS code, we provide getBlock, an utility function that pulls code from an editor block. Blocks in a Codemirror editor instance are delimited by ____ (3 or more underscores).

  const evalLiveCode = () => {
    if(engine){
      try{
        const { errors, dspCode } = compile( editorGrammar.getValue(), editorLivecode.getValue() );
        if(dspCode){
          console.info(editorLivecode.getValue());
          engine.eval(dspCode);
        }
      } catch (err) {
        console.error("ERROR: Failed to compile and eval: ", err);
      }
    }
    else throw new Error('ERROR: Engine not initialized. Please press Start Engine first.')
  }

  const evalJs = async () => {
    if(learner && editorJS){
      const code = getBlock(editorJS);
      console.info(code);
      learner.eval(code);
    }
    else throw new Error('ERROR: Learner not initialized. Please press Create Learner first.')
  }

Documentation

The sema-engine has small API surface that you can find more about on this project's wiki.

Contributing

Pull requests are wellcome but please observe the Contributing guidelines.

Related Publications

Bernardo, F., Kiefer, C., Magnusson, T. (2020). A Signal Engine for a Live Code Language Ecosystem. Journal of Audio Engineering Society, Vol. 68, No. 1, October, DOI: https://doi.org/10.17743/jaes.2020.0016