Expand description
Library for pure Rust advanced audio synthesis.
Most audio DSP (Digital Signal Processing) libraries have a concept of an audio graph which connects sources to destinations. Twang uses a simplified model: a synthesis tree (a dependency tree of sorts, a type of DAG - directed acyclic graph, but limited to a single root node). Twang doesn’t deal with having speakers as a node on a graph, as it’s only focus is synthesis. A synthesis tree can do all of the things that an audio graph can do, but it’s simpler and much easier to learn.
To start, first you need to construct a synthesizer
(Synth). Then you need a type that implements the
Sink trait. Audio buffers have a sink method you can use to get a
Sink. Once you have those, you can synthesize audio with a closure that
has one parameter representing the frequency counter. You can use the
frequency counter to generate continuous pitched waveforms.
A3 (220 Hz) Minor Piano Example
This example uses the first ten piano harmonics to generate a sound that sounds like an electric piano. This is an example of additive synthesis.
use fon::chan::Ch16;
use fon::{Audio, Frame};
use twang::noise::White;
use twang::ops::Gain;
use twang::osc::Sine;
use twang::Synth;
/// First ten harmonic volumes of a piano sample (sounds like electric piano).
const HARMONICS: [f32; 10] = [
0.700, 0.243, 0.229, 0.095, 0.139, 0.087, 0.288, 0.199, 0.124, 0.090,
];
/// The three pitches in a perfectly tuned A3 minor chord
const PITCHES: [f32; 3] = [220.0, 220.0 * 32.0 / 27.0, 220.0 * 3.0 / 2.0];
/// Volume of the piano
const VOLUME: f32 = 1.0 / 3.0;
// State of the synthesizer.
#[derive(Default)]
struct Processors {
// White noise generator.
white: White,
// 10 harmonics for 3 pitches.
piano: [[Sine; 10]; 3],
}
fn main() {
// Initialize audio
let mut audio = Audio::<Ch16, 2>::with_silence(48_000, 48_000 * 5);
// Create audio processors
let mut proc = Processors::default();
// Adjust phases of harmonics.
for pitch in proc.piano.iter_mut() {
for harmonic in pitch.iter_mut() {
harmonic.shift(proc.white.step());
}
}
// Build synthesis algorithm
let mut synth = Synth::new(proc, |proc, mut frame: Frame<_, 2>| {
for (s, pitch) in proc.piano.iter_mut().zip(PITCHES.iter()) {
for ((i, o), v) in s.iter_mut().enumerate().zip(HARMONICS.iter()) {
// Get next sample from oscillator.
let sample = o.step(pitch * (i + 1) as f32);
// Pan the generated harmonic center
frame = frame.pan(Gain.step(sample, (v * VOLUME).into()), 0.0);
}
}
frame
});
// Synthesize 5 seconds of audio
synth.stream(audio.sink());
}