wavegl

Generate Audio in the GPU and stream to the Audio Card.

WebGL + Web Audio API.

JS Libraries:

Some code taken from GLSL.io.

The idea

We can implement a DSP function in a GLSL Fragment. A texture will package a buffer of DSPs calls.
The DSP signal must be encoded in a scanline direction: colors, left-right, top-bottom,
Then we can just use the buffer of the texture as an audio chunk: We just have to schedule this buffer with Web Audio API.
Then, we just do this loop again each second :-)

A 105 x 105 image is enough to code 1 second of audio (1-channel, 44100Hz, 8bit-samples). Rendering a 105x105 image each second is nothing :-)

Proof of Concept

WebGL uses GLSL language: a C-like, but with high level types and math functions.

https://www.khronos.org/registry/webgl/specs/latest/1.0/#readpixels

function readPixels (gl, width, height) {
  var pixels = new Uint8Array(width * height * 4);
  gl.readPixels(0, 0, width, height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
  return pixels;
}

http://www.w3.org/TR/webaudio/

var audioCtx = new AudioContext();
var playTime = audioCtx.currentTime;
var bufferSource = context.createBufferSource();
bufferSource.buffer = pixels;
bufferSource.start(time);
setInterval(function schedulingLoop () {
  if (endOfTheScheduledAudioIsSoon()) {
    scheduleNext();
  }
}, 100);

Notes:

The GLSL code will have to encode the image in order that it respect the readPixels order: RGBA, left to right, top to bottom. Then we can just plug this into the Audio Card !!
Render one frame in the GPU is very fast.
a texture of 105x105 is enough to generate 1 second of sound. (44100 samples – 105x105x4)

Then we can make a wrapper to only have to implement this:

const float PI = acos(-1.0)
float dsp (float t) {
  return 0.1 * sin(2.0 * PI * t * 440); // Hello world of the audio
}

About "Functional Audio"

"Functional Audio" is a low level way to generate music, quite different from Web Audio API paradigm (modular audio).

dsp: (t: Number) => (sample: Float)

t: absolute time in seconds.

sample: value from -1.0 to 1.0. Amplitude of the sound.

This function is called 44'100 times per second!

It is:

Generative audio.
Low Level.
Pure Math.

The team

@dohzya
@c4m
@guyonvarch
@gre

Bootstraped in Hackday @zengularity

License

AGPLv3

Build the project

First time:

npm install

Then:

npm run build

Then open index.html.

Watch loop for development:

npm run watch

Known limitations

the main idea is to have this pipeline: GLSL (GPU) -> readPixels -> WebAudioAPI (Audio Card). No overhead of JS, pipe an Uint8Array from the GPU to the Audio Card !

The idea is a hack at the start but they could be some real potential :-)

The GLSL have limitation for such hack usage though :-D After like 2 minutes you will start notice some noise in the sound, well that is due to float imprecision (I also had to use a float in second instead of an int sample number) + there is no support for binary logic operator so we can't make ByteBeat + Latency is an issue if you want to have user interaction.

gre / wavegl