Rendering and live playback

A sound is a description. To hear it or keep it, you render it. There are three ways, from simplest to most flexible.

Render to memory

Render(seconds, sampleRate) produces an AudioBuffer you can inspect or pass along:

using static Sigil.Sound.Sounds;

var buffer = (Saw(110).LowPass(900) * 0.4).Render(seconds: 4, sampleRate: 48_000);

Use it for tests, for analysis, or to build a longer piece from short parts.

Render to a WAV file

RenderToWav writes the same audio to disk, as 16, 24-bit or 32-bit float WAV, to a path or a stream:

using static Sigil.Sound.Sounds;

var mix = (Saw(110).LowPass(900) * 0.4).Limit();
mix.RenderToWav("demo.wav", seconds: 8, sampleRate: 48_000);

To capture a stretch from well into a sound, pass startSeconds. The skipped part is still run and thrown away, so oscillators, envelopes, delay lines and filters are in the state they would have reached by then, and the result matches that stretch of a longer render from zero. Render takes it too:

using static Sigil.Sound.Sounds;

// Eight seconds of the mix, beginning two minutes in.
var mix = (Saw(110).LowPass(900) * 0.4).Limit();
mix.RenderToWav("demo-later.wav", seconds: 8, sampleRate: 48_000, startSeconds: 120);

Skipping costs the time of rendering the skipped part, since there is no way to jump a stateful sound ahead without running it.

The file-path overload is not allowed inside the REPL: it cannot write to a disk there.

Live playback

SoundContext is a running output. You play a sound into it and replace it at any time. A replaced sound crossfades in over the old one.

using static Sigil.Sound.Sounds;
using Sigil.Sound;

using var context = new SoundContext();
context.Play(Saw(110).LowPass(900) * 0.4, fadeSeconds: 0.5);

// Later, from the audio callback or a test: pull frames from the context.
// context.Render(span);

context.Stop(fadeSeconds: 1.0);

Time reports how many seconds have been rendered. A host calls Render(span) from its own audio callback.

Swappable locations

A Slot marks a place in a graph where the sound can be changed later. Replacing it compiles the new sound off the audio thread and crossfades to it atomically.

using static Sigil.Sound.Sounds;
using Sigil.Sound;

var slot = new Slot(Saw(110) * 0.4);
var patch = slot.Sound.Gain(0.8);   // use the slot anywhere a Sound goes

// Later, from any thread:
slot.Swap(Saw(165) * 0.4, fadeSeconds: 0.2);

Use a slot when a graph is built once but its contents should change while it runs, for example a live-coding host.