MIDI to milliseconds

This library provides a TimeResolver class that yields TimeResolvedTracks and TimeResolvedEvents from a MIDI file.

For use with this MIDI package.

Installation

npm install @perry-rylance/midi-to-milliseconds

Usage

You'll need a MIDI file with one or more tracks loaded up, see @perry-rylance/midi.

const resolver = new TimeResolver(midi);
const track = resolver.tracks[0];
const events = track.getEventsBetweenMilliseconds(0, 1000);

events will be an array of TimeResolvedEvent objects, containing the events resolved absolute ticks and milliseconds in absolute and the original event in original.

This is useful for tasks such as syncing animations to MIDI. If track milliseconds for the previous frame versus milliseconds at the time now for example, you can retrieve a list of MIDI events that occured within that frame. From there you can do something like animate objects based on the events.

Stability

By default, getEventsBetweenMilliseconds and getEventsBetweenTicks are not stable. They will return the events between the specified start and end, however the events will not necessarily be in their original order.

For applications that only care about which events occured and not what order they occured in, this is fine. For example, a visual application that only cares about note on events on the current frame may not care what order those events are retrieved in.

For applications that must preserve the order of events please initialize the TimeResolver with {stable: true} as the options argument. At a slight performance cost, this will guarantee events are returned in the same order they appeared in the original MIDI file. This is useful for accuracy-critial applications such as realtime MIDI playback.

Under the hood, this library uses d3-binarytree to very quickly find events between specified times. This is not stable. When passing true for the stable option, this library will keep an index of the events and use JavaScript's sort before returning events between specified times.