# LV2 Time

A vocabulary for describing musical time.

ID | http://lv2plug.in/ns/ext/time
Version | 1.6
Date | 2021-01-09
Discuss | devel@lists.lv2plug.in (subscribe)

- Index
- History
- API

This is a vocabulary for describing a position in time and the speed of time passage, in both real and musical terms.

In addition to real time (based on seconds), two units of time are used: frames and beats. A frame is a numbered quantum of time. Frame time is related to real-time by the frame rate or sample rate, framesPerSecond. A beat is a single pulse of musical time. Beat time is related to real-time by the tempo, beatsPerMinute.

Musical time additionally has a meter which describes passage of time in terms of musical bars. A bar is a higher level grouping of beats. The meter describes how many beats are in one bar.

## Index

Classes | Properties
--- | ---
Position Rate Time | bar barBeat beat beatUnit beatsPerBar beatsPerMinute frame framesPerSecond position speed

## Classes

### Position

Class

Label | Position
Superclass of | Rate
| Time
In range of | position

A point in time and/or the speed at which time is passing.

A point in time and/or the speed at which time is passing. A position is both a point and a speed, which precisely defines a time within a timeline.

### Rate

Class

Label | Rate
Subclass of | Position
In domain of | beatUnit
| beatsPerBar
| beatsPerMinute
| framesPerSecond
| speed

The rate of passage of time.

The rate of passage of time in terms of one unit with respect to another.

### Time

Class

Label | Time
Subclass of | Position
In domain of | bar
| barBeat
| beat
| frame

A point in time in some unit/dimension.

## Properties

### bar

Property

Label | bar
Domain | Time
Range | xsd:long
Type | Datatype Property

A musical bar or measure.

### barBeat

Property

Label | beat within bar
Domain | Time
Range | xsd:float
Type | Datatype Property

The beat number within the bar, from 0 to beatsPerBar.

### beat

Property

Label | beat
Domain | Time
Range | xsd:double
Type | Datatype Property

The global running beat number.

This is not the beat within a bar like barBeat, but relative to the same origin as bar and monotonically increases unless the transport is repositioned.

### beatUnit

Property

Label | beat unit
Domain | Rate
Range | xsd:nonNegativeInteger
Type | Datatype Property

The note value that counts as one beat.

Beat unit, the note value that counts as one beat. This is the bottom number in a time signature: 2 for half note, 4 for quarter note, and so on.

### beatsPerBar

Property

Label | beats per bar
Domain | Rate
Range | xsd:float
Type | Datatype Property

The number of beats in one bar.

### beatsPerMinute

Property

Label | beats per minute
Domain | Rate
Range | xsd:float
Type | Datatype Property

Tempo in beats per minute.

### frame

Property

Label | frame
Domain | Time
Range | xsd:long
Type | Datatype Property

A time stamp in audio frames.

### framesPerSecond

Property

Label | frames per second
Domain | Rate
Range | xsd:float
Type | Datatype Property

Frame rate in frames per second.

### position

Property

Label | position
Range | Position
Type | Object Property

A musical position.

### speed

Property

Label | speed
Domain | Rate
Range | xsd:float
Type | Datatype Property

The rate of the progress of time as a fraction of normal speed.

The rate of the progress of time as a fraction of normal speed. For example, a rate of 0.0 is stopped, 1.0 is rolling at normal speed, 0.5 is rolling at half speed, -1.0 is reverse, and so on.

## History

Version 1.6 (2019-02-03)
  - Clarify time:beat origin.
Version 1.4 (2016-07-31)
  - Define LV2_TIME_PREFIX.
Version 1.2 (2012-10-14)
  - Use consistent label style.
Version 1.0 (2012-04-17)
  - Initial release.