# LV2 Parameters

Common parameters for audio processing.

ID | http://lv2plug.in/ns/ext/parameters
Version | 1.4
Date | 2020-04-26
Discuss | devel@lists.lv2plug.in (subscribe)

- Index
- History
- API

This is a vocabulary for parameters that are common in audio processing software. A parameter is purely a metadata concept, unrelated to any particular code mechanism. Parameters are used to assign meaning to controls (for example, using lv2:designation for ports) so they can be used more intelligently or presented to the user more efficiently.

## Index

Classes | Instances
--- | ---
ControlGroup CompressorControls EnvelopeControls FilterControls OscillatorControls | amplitude attack bypass cutoffFrequency decay delay dryLevel frequency gain hold pulseWidth ratio release resonance sampleRate sustain threshold waveform wetDryRatio wetLevel

## Classes

### CompressorControls

Class

Label | Compressor Controls
Subclass of | ControlGroup
pg:element |
lv2:designation | threshold
pg:element |
lv2:designation | ratio

Typical controls for a compressor.

### ControlGroup

Class

Label | Control Group
Subclass of | pg:Group
Superclass of | CompressorControls
| EnvelopeControls
| FilterControls
| OscillatorControls

A group representing a set of associated controls.

### EnvelopeControls

Class

Label | Envelope Controls
Subclass of | ControlGroup
pg:element |
lv2:designation | delay
lv2:index | 0
pg:element |
lv2:designation | attack
lv2:index | 1
pg:element |
lv2:designation | hold
lv2:index | 2
pg:element |
lv2:designation | decay
lv2:index | 3
pg:element |
lv2:designation | sustain
lv2:index | 4
pg:element |
lv2:designation | release
lv2:index | 5

Typical controls for a DAHDSR envelope.

### FilterControls

Class

Label | Filter Controls
Subclass of | ControlGroup
pg:element |
lv2:designation | cutoffFrequency
pg:element |
lv2:designation | resonance

Typical controls for a filter.

### OscillatorControls

Class

Label | Oscillator Controls
Subclass of | ControlGroup
pg:element |
lv2:designation | frequency
pg:element |
lv2:designation | amplitude
pg:element |
lv2:designation | waveform
pg:element |
lv2:designation | pulseWidth

Typical controls for an oscillator.

## Instances

### amplitude

Instance

Label | amplitude
Type | lv2:Parameter

An amplitude as a factor, where 0 is silent and 1 is unity.

### attack

Instance

Label | attack
Type | lv2:Parameter

The duration of an envelope attack stage.

### bypass

Instance

Label | bypass
Type | lv2:Parameter

A boolean parameter that disables processing if true.

### cutoffFrequency

Instance

Label | cutoff frequency
Type | lv2:Parameter

The cutoff frequency, typically in Hz, for a filter.

### decay

Instance

Label | decay
Type | lv2:Parameter

The duration of an envelope decay stage.

### delay

Instance

Label | delay
Type | lv2:Parameter

The duration of an envelope delay stage.

### dryLevel

Instance

Label | dry level
Type | lv2:Parameter

The level of the unprocessed component of a signal.

### frequency

Instance

Label | frequency
Type | lv2:Parameter

A frequency, typically in Hz.

### gain

Instance

Label | gain
Type | lv2:Parameter
units:unit | units:db
lv2:default | 0.0
lv2:maximum | 20.0
lv2:minimum | -20.0

Gain in decibels.

### hold

Instance

Label | hold
Type | lv2:Parameter

The duration of an envelope hold stage.

### pulseWidth

Instance

Label | pulse width
Type | lv2:Parameter

The width of a pulse of a rectangular waveform.

### ratio

Instance

Label | ratio
Type | lv2:Parameter

Compression ratio.

### release

Instance

Label | release
Type | lv2:Parameter

The duration of an envelope release stage.

### resonance

Instance

Label | resonance
Type | lv2:Parameter

The resonance of a filter.

### sampleRate

Instance

Label | sample rate
Type | lv2:Parameter

A sample rate in Hz.

### sustain

Instance

Label | sustain
Type | lv2:Parameter

The level of an envelope sustain stage as a factor.

### threshold

Instance

Label | threshold
Type | lv2:Parameter

Compression threshold.

### waveform

Instance

Label | waveform
Type | lv2:Parameter

The waveform "fader" for oscillators or modulators that have several.

### wetDryRatio

Instance

Label | wet/dry ratio
Type | lv2:Parameter

The ratio between processed and bypassed levels in the output.

The ratio between processed and bypass components in output signal. The dry and wet percentages can be calculated from the following equations:

    dry = (wetDryRatio.maximum - wetDryRatio.value) / wetDryRatio.maximum
    wet = wetDryRatio.value / wetDryRatio.maximum

Typically, maximum value of 1 or 100 and minimum value of 0 should be used.

### wetLevel

Instance

Label | wet level
Type | lv2:Parameter

The level of the processed component of a signal.

## History

Version 1.4 (2015-04-07)
  - Add range to parameters so hosts know how to control them.
Version 1.2 (2012-10-14)
  - Use consistent label style.
  - Add param:sampleRate.
  - Add parameters.h of URI defines for convenience.
Version 1.0 (2012-04-17)
  - Initial release.