Signal

The Signal class implements a piecewise automation curve for scalar parameters such as BPM. It stores automation points and evaluates the curve at any audio time, supporting step, linear, and exponential ramps.

(no submodules)

Purpose

Musical performances often require smooth tempo changes. Signal provides the mathematical foundation for these changes by scheduling automation points and interpolating between them. The TickSource reads the BPM curve through this Signal so that tempo ramps produce a continuously varying tick rate.

Features

setValueAtTime for step changes
linearRampToValueAtTime for linear interpolation
exponentialRampToValueAtTime for exponential curves
getValueAtTime for curve evaluation at arbitrary times
cancelScheduledValues for clearing future points
Rejects non-positive and non-finite values with AUDIO_TRANSPORT_INVALID_BPM

Usage: Basic

import { Signal } from "@suaveplan/audio-transport";

const bpm = new Signal({ initialValue: 120 });
bpm.linearRampToValueAtTime(240, 1);
console.log(bpm.getValueAtTime(0.5)); // 180

Usage: Advanced

const bpm = new Signal({ initialValue: 100 });
bpm.setValueAtTime(120, 0.5);
bpm.exponentialRampToValueAtTime(240, 1.5);
console.log(bpm.getValueAtTime(1)); // ~169.7

API Reference

Constructor

new Signal(options?)

Properties

initialValue — value before any points
value — convenience getter returning value at time 0
points — readonly array of automation points

Methods

setValueAtTime(value, time) — step change
linearRampToValueAtTime(value, time) — linear ramp
exponentialRampToValueAtTime(value, time) — exponential ramp
getValueAtTime(time) — evaluate curve
cancelScheduledValues(time) — remove points at or after time

Implementation Notes

Points are stored sorted by time. Exponential ramps require strictly positive start and target values; otherwise AUDIO_TRANSPORT_INVALID_BPM is thrown. The curve evaluation handles interpolation before the first point, between points, and after the last point.

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