RustySynth

RustySynth is a SoundFont MIDI synthesizer written in pure Rust, ported from MeltySynth.

I made it support multi-threaded rendering by using rayon so I could render some black MIDIs.

DO NOT open the exported wav file directly and listen to it, it is very loud!

Features

• Suitable for both real-time and offline synthesis. For offline only
• Supports standard MIDI files with additional features including dynamic tempo changing. Currently only MIDI 1 is supported
• No dependencies other than the standard library.
• It only took about 50 seconds to render 9KX2.

Demo

This is a demo video to show the synthesizer running on rust-sfml in real-time.

https://www.youtube.com/watch?v=o9rPTJIPmVk

Installation

RustySynth is available on crates.io:

cargo add rustysynth

Examples

An example code to synthesize a simple chord:

// Load the SoundFont.
let mut sf2 = File::open("TimGM6mb.sf2").unwrap();
let sound_font = Arc::new(SoundFont::new(&mut sf2).unwrap());

// Create the synthesizer.
let settings = SynthesizerSettings::new(44100);
let mut synthesizer = Synthesizer::new(&sound_font, &settings).unwrap();

// Play some notes (middle C, E, G).
synthesizer.note_on(0, 60, 100);
synthesizer.note_on(0, 64, 100);
synthesizer.note_on(0, 67, 100);

// The output buffer (3 seconds).
let sample_count = (3 * settings.sample_rate) as usize;
let mut left: Vec<f32> = vec![0_f32; sample_count];
let mut right: Vec<f32> = vec![0_f32; sample_count];

// Render the waveform.
synthesizer.render(&mut left[..], &mut right[..]);

Another example code to synthesize a MIDI file:

// Load the SoundFont.
let mut sf2 = File::open("TimGM6mb.sf2").unwrap();
let sound_font = Arc::new(SoundFont::new(&mut sf2).unwrap());

// Load the MIDI file.
let mut mid = File::open("flourish.mid").unwrap();
let midi_file = Arc::new(MidiFile::new(&mut mid).unwrap());

// Create the MIDI file sequencer.
let settings = SynthesizerSettings::new(44100);
let synthesizer = Synthesizer::new(&sound_font, &settings).unwrap();
let mut sequencer = MidiFileSequencer::new(synthesizer);

// Play the MIDI file.
sequencer.play(&midi_file, false);

// The output buffer.
let sample_count = (settings.sample_rate as f64 * midi_file.get_length()) as usize;
let mut left: Vec<f32> = vec![0_f32; sample_count];
let mut right: Vec<f32> = vec![0_f32; sample_count];

// Render the waveform.
sequencer.render(&mut left[..], &mut right[..]);

Yet another example code to synthesize a MIDI file in real-time with TinyAudio:

// Setup the audio output.
let params = OutputDeviceParameters {
    channels_count: 2,
    sample_rate: 44100,
    channel_sample_count: 4410,
};

// Buffer for the audio output.
let mut left: Vec<f32> = vec![0_f32; params.channel_sample_count];
let mut right: Vec<f32> = vec![0_f32; params.channel_sample_count];

// Load the SoundFont.
let mut sf2 = File::open("TimGM6mb.sf2").unwrap();
let sound_font = Arc::new(SoundFont::new(&mut sf2).unwrap());

// Load the MIDI file.
let mut mid = File::open("flourish.mid").unwrap();
let midi_file = Arc::new(MidiFile::new(&mut mid).unwrap());

// Create the MIDI file sequencer.
let settings = SynthesizerSettings::new(params.sample_rate as i32);
let synthesizer = Synthesizer::new(&sound_font, &settings).unwrap();
let mut sequencer = MidiFileSequencer::new(synthesizer);

// Play the MIDI file.
sequencer.play(&midi_file, false);

// Start the audio output.
let _device = run_output_device(params, {
    move |data| {
        sequencer.render(&mut left[..], &mut right[..]);
        for (i, value) in left.iter().interleave(right.iter()).enumerate() {
            data[i] = *value;
        }
    }
})
.unwrap();

// Wait for 10 seconds.
std::thread::sleep(std::time::Duration::from_secs(10));

Todo

• Wave synthesis
  • SoundFont reader
  • Waveform generator
  • Envelope generator
  • Low-pass filter
  • Vibrato LFO
  • Modulation LFO
• MIDI message processing
  • Note on/off
  • Bank selection
  • Modulation
  • Volume control
  • Pan
  • Expression
  • Hold pedal
  • Program change
  • Pitch bend
  • Tuning
• Effects
  • Reverb
  • Chorus
• Other things
  • Standard MIDI file support
  • MIDI file loop extension support
  • Performace optimization

License

RustySynth is available under the MIT license.