# LV2 Parameters

http://lv2plug.in/ns/ext/parameters
Common parameters for audio processing.

Version | 1.4
Date | 2018-03-16
Discuss | devel@lists.lv2plug.in (subscribe)
Developer | Lars Luthman
Maintainer | David Robillard

- Index
- Reference
- History
- API

This vocabulary describes parameters 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 (e.g. using lv2:designation for ports) so they can be used more intelligently or presented to the user more efficiently.

## Index

Classes | Instances | Files
--- | --- | ---
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 | lv2-parameters.doap.ttl parameters.ttl

## Reference

### Class param:CompressorControls

Compressor Controls

Sub-class of | param:ControlGroup
pg:element |
lv2:designation | param:threshold
pg:element |
lv2:designation | param:ratio

### Class param:ControlGroup

A group representing a set of associated controls.

Sub-class of | pg:Group

### Class param:EnvelopeControls

DAHDSR Envelope Controls

Sub-class of | param:ControlGroup
pg:element |
lv2:designation | param:delay
lv2:index | 0
pg:element |
lv2:designation | param:attack
lv2:index | 1
pg:element |
lv2:designation | param:hold
lv2:index | 2
pg:element |
lv2:designation | param:decay
lv2:index | 3
pg:element |
lv2:designation | param:sustain
lv2:index | 4
pg:element |
lv2:designation | param:release
lv2:index | 5

### Class param:FilterControls

Filter Controls

Sub-class of | param:ControlGroup
pg:element |
lv2:designation | param:cutoffFrequency
pg:element |
lv2:designation | param:resonance

### Class param:OscillatorControls

Oscillator Controls

Sub-class of | param:ControlGroup
pg:element |
lv2:designation | param:frequency
pg:element |
lv2:designation | param:amplitude
pg:element |
lv2:designation | param:waveform
pg:element |
lv2:designation | param:pulseWidth

### Instance param:amplitude

amplitude

Type | lv2:Parameter

### Instance param:attack

attack

The duration of an envelope's attack stage.

Type | lv2:Parameter

### Instance param:bypass

bypass

A boolean parameter that disabled processing if true.

Type | lv2:Parameter

### Instance param:cutoffFrequency

cutoff frequency

Type | lv2:Parameter

### Instance param:decay

decay

The duration of an envelope's decay stage.

Type | lv2:Parameter

### Instance param:delay

delay

The duration of an envelope's delay stage.

Type | lv2:Parameter

### Instance param:dryLevel

dry level

The level of the unprocessed component of a signal.

Type | lv2:Parameter

### Instance param:frequency

frequency

Type | lv2:Parameter

### Instance param:gain

gain

Gain in decibels.

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

### Instance param:hold

hold

The duration of an envelope's hold stage.

Type | lv2:Parameter

### Instance param:pulseWidth

pulse width

The width of a pulse of a rectangular waveform.

Type | lv2:Parameter

### Instance param:ratio

ratio

Compression ratio.

Type | lv2:Parameter

### Instance param:release

release

The duration of an envelope's release stage.

Type | lv2:Parameter

### Instance param:resonance

resonance

The resonance of a filter.

Type | lv2:Parameter

### Instance param:sampleRate

sample rate

A sample rate in Hz.

Type | lv2:Parameter

### Instance param:sustain

sustain

The level (not duration) of an envelope's sustain stage.

Type | lv2:Parameter

### Instance param:threshold

threshold

Compression threshold.

Type | lv2:Parameter

### Instance param:waveform

waveform

Type | lv2:Parameter

### Instance param:wetDryRatio

wet/dry ratio

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.

Type | lv2:Parameter

### Instance param:wetLevel

wet level

The level of the processed component of a signal.

Type | lv2:Parameter

## History

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