RustySynth-ext

RustySynth-ext is a fork of RustySynth — a SoundFont MIDI synthesizer written in pure Rust, ported from MeltySynth — that adds optional SoundFont3 (.sf3) support on top of the upstream SoundFont2 (.sf2) support.

Features

• Suitable for both real-time and offline synthesis.
• Supports standard MIDI files with additional features including dynamic tempo changing.
• No dependencies other than the standard library by default.
• Optional SoundFont3 (.sf3) support.

SF3 SoundFonts store their samples as Ogg Vorbis streams instead of raw PCM, roughly 10x smaller than the equivalent SF2. Loading them is opt-in because it adds the pure-Rust lewton decoder:

cargo add rustysynth-ext --features sf3

With the sf3 feature enabled, SoundFont::new loads .sf3 files transparently, decompressing every sample into the same 16-bit PCM layout used by .sf2 files.

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[..]);

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
  • Performance optimization

License

RustySynth-ext is available under the MIT license. It is a fork of RustySynth, whose copyright notice is preserved in the license text.