a2aaron / midly

A feature-complete MIDI parser and writer focused on speed.

Midly

Midly is a MIDI decoder and encoder designed for efficiency and completeness, supporting both .mid files and real-time MIDI streams while making minimal allocations.

See the crate-level documentation for the available features and no_std support.

Getting started

First add the following line to your Cargo.toml file, under the [dependencies] section:

midly = "0.5"

Then use the Smf type in the crate root:

// Load bytes first
let data = std::fs::read("Pi.mid").unwrap();

// Parse the raw bytes
let mut smf = midly::Smf::parse(&data).unwrap();

// Use the information
println!("midi file has {} tracks!", smf.tracks.len());

// Modify the file
smf.header.format = midly::Format::Sequential;

// Save it back
smf.save("PiRewritten.mid").unwrap();

Or use the LiveEvent type to parse real-time MIDI events:

use midly::{live::LiveEvent, MidiMessage};

fn on_midi(event: &[u8]) {
    let event = LiveEvent::parse(event).unwrap();
    match event {
        LiveEvent::Midi { channel, message } => match message {
            MidiMessage::NoteOn { key, vel } => {
                println!("hit note {} on channel {}", key, channel);
            }
            _ => {}
        },
        _ => {}
    }
}

Most types to be imported are on the crate root and are documented in-place. Check the crate documentation for more information.

Speed

Although performance is not critical in a MIDI library, it still is an important objective of the midly library, providing automatic multithreading and minimal allocations. The following chart presents benchmark results against other MIDI libraries in the ecosystem capable of reading .mid files. The benchmarks were done on a warm file cache.

File name	File size	rimd 0.0.1	nom-midi 0.5.1	midly 0.5.2
Clementi.mid	4 KB	11 ms	Error	0.15 ms
CrabRave.mid	53 KB	145 ms	0.55 ms	0.26 ms
Beethoven.rmi	90 KB	Error	Error	0.48 ms
Pi.mid	24 MB	66700 ms	358 ms	85 ms
PiDamaged.mid	64 KB	Freeze	Error	0.55 ms

The above results are only referential, actual performance depends on the hardware and operating system.