Class Lfo

Namespace

NAudio.Dsp

Assembly

NAudio.Core.dll

A bipolar (-1..+1) low-frequency oscillator for modulation (chorus, flanger, phaser, tremolo, auto-pan). Allocation-free; the sample-and-hold waveform uses a deterministic generator so output is reproducible.

public sealed class Lfo

Inheritance

object

Lfo

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Constructors

Lfo(int)

Creates an LFO.

public Lfo(int sampleRate)

Parameters

sampleRate int

Sample rate in Hz. Must be positive.

Properties

DelaySeconds

An optional delay in seconds before the LFO starts oscillating. During the delay Process() outputs 0 (the bipolar neutral value), matching the SoundFont/SFZ LFO delay behaviour. The delay is re-armed by Reset().

public float DelaySeconds { get; set; }

Property Value

float

FrequencyHz

Oscillation frequency in Hz. Must be positive.

public float FrequencyHz { get; set; }

Property Value

float

SampleRate

Sample rate in Hz. Must be positive.

public int SampleRate { get; set; }

Property Value

int

StartPhase

The phase, as a fraction of a cycle in [0, 1), that the oscillator starts from. Setting it moves the current phase there immediately (like Reset(), which also re-applies it); values outside [0, 1) wrap. The default of 0 keeps the historical behaviour (triangle and square start at +1, sine and sawtooth rising through their zero / minimum). Because the phase does not advance during DelaySeconds, the first sample after the delay expires is taken at this phase — a SoundFont LFO (SF2.04 §8.1.2 gens 21/23) "begins its upward ramp from zero" when its delay elapses, which for the triangle waveform is a start phase of 0.75.

public float StartPhase { get; set; }

Property Value

float

Waveform

Oscillator waveform. Default Sine.

public LfoWaveform Waveform { get; set; }

Property Value

LfoWaveform

Methods

Advance(int)

Advances the oscillator by samples samples in one call, returning the value the last of that many Process() calls would have returned (0 while the delay is still running; for samples = 0 the state is untouched and the value the next call will return is reported). The resulting state is bit-identical to repeated Process() calls: the delay countdown is consumed in O(1), and the phase accumulator is stepped with the same per-sample additions Process performs (a closed-form phase + n x increment would round differently), but the waveform — the dominant per-sample cost — is evaluated only once. Intended for control-rate consumers that read the LFO once per block.

public float Advance(int samples)

Parameters

samples int

Number of samples to advance by. Must not be negative.

Returns

float

Process()

Advances one sample and returns the next oscillator value in [-1, 1].

public float Process()

Returns

float

Reset()

Resets the phase to StartPhase (and re-seeds the sample-and-hold generator).

public void Reset()

SyncToTempo(double, NoteDivision)

Sets FrequencyHz from a tempo and note division.

public void SyncToTempo(double bpm, NoteDivision division)

Parameters

bpm double

division NoteDivision