The WebAudio API is designed around the concept of audio processing nodes. Each of these nodes can have zero or more audio inputs, as well as zero or more audio outputs.

The WebAudio API is designed around the concept of audio processing nodes. Each of these nodes can have zero or more audio inputs, as well as zero or more audio outputs. When we create a RNBO device, we also create a WebAudio node that wraps the exported RNBO code. This makes it easy to use multiple RNBO devices together in an audio processing chain.

// This code assumes that we have two RNBO patches, one exported as synth.export.json,
// and one exported as effect.export.json
const { createDevice } = require ("@rnbo/js");

async function setup() {
    const WAContext = window.AudioContext || window.webkitAudioContext;
    const context = new WAContext();

    // Create gain node and connect it to audio output
    const outputNode = context.createGain();
    outputNode.connect(context.destination);
    
    // Fetch the exported patchers
    let response = await fetch("export/synth.export.json");
    const synthPatcher = await response.json();
    response = await fetch("export/effect.export.json");
    const effectPatcher = await response.json();

    // Create the devices
    const synthDevice = await createDevice({ context, patcher: synthPatcher });
    const effectDevice = await createDevice({ context, patcher: effectPatcher });

    // Connect the devices in series
    synthDevice.node.connect(effectDevice.node);
    effectDevice.node.connect(outputNode);
}

setup();

Splitting and Merging Audio Channels

As mentioned, a WebAudio node can have multiple input and output channels. The node property of a RNBO device has as many input channels as the exported RNBO patcher has in~ indexes, and as many output channels as the patcher has out~ indexes. The connect method of a WebAudio node has two optional arguments, one for the output index and one for the input index. Using these arguments, one could take a monophonic RNBO device and pass it through a stereo effect.

// Create the devices
const synthDevice = await createDevice({ context, patcher: synthPatcher });
const effectDevice = await createDevice({ context, patcher: effectPatcher });

// Diffuse the monophonic output of the synthesizer into stereo 
synthDevice.node.connect(effectDevice.node, 0, 0);
synthDevice.node.connect(effectDevice.node, 0, 1);
effectDevice.node.connect(outputNode);

For more information, check the API documentation for AudioNode, and the documentation for the AudioContext functions createChannelSplitter and createChannelMerger.

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