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unitgen

unitgen

unitgen is a Node.js powered unit-generator API, built using streams and the speaker bindings.

unitgen was built for a demo being given at Dance.js.

In a nutshell

Unit generators are best thought of as a graph of transformations applied to an audio-stream.

This can be used to:

  • apply effects (changing tempo, changing pitch, applying distortion).
  • mix together and pan-between multiple tracks.
  • pan between left and right stereo.

How does it work?

  • unitgen's speaker binding invokes a callback which samples from a stream 44100 times a second.
  • the stream takes a snapshot of the current state of all the unit-generators, and outputs a frame of audio.
  • a frame of audio consists of bytes indicating the speaker position for left and right audio.

Installing

npm install unitgen -g

Examples

So that you can get an idea of unitgen in action, we've provided a few sample unit-generator-graphs. For each example, use a and s to pan back and forth.

  • stereo.js: uses a function unit-generator to play a sine-wave which can be panned between the left and right speaker.
unitgen stereo
  • canceling.js: uses a combiner, and two function unit-generators to play two inverse sine-waves. Pan back and forth to hear them cancel out.
unitgen canceling
  • mixer.js: uses a combiner, and two sound-file unit-generators to pan between two songs.
unitgen mixer --track1=./foo.wav --track2=./foo2.wav

The future

unitgen is a rough proof of concept. Over time we'd love to see this grow into a full-featured API for building (as a practical example) mixers in JavaScript.

patches welcome!