RustySynth SoundFont MIDI Synthesizer

To render a MIDI file to audio buffers (offline synthesis), use the MidiFileSequencer. This wraps a Synthesizer and allows you to play a MidiFile before calling render to generate the waveform based on the MIDI file's duration.

// 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[..]);

To synthesize specific notes without a MIDI file, you can use the Synthesizer directly. You must load a SoundFont, initialize SynthesizerSettings with a sample rate, and then call note_on for each note. Finally, use render to fill stereo output buffers.

// 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[..]);

For real-time audio playback, integrate MidiFileSequencer with an audio output device (e.g., using the TinyAudio crate). In the audio callback, call sequencer.render to fill the output buffers and interleave the left and right channels for the device.

// 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));

The Preset struct represents a single instrument preset within a SoundFont. It contains metadata such as the preset name, patch number, bank number, and other classification info (library, genre, morphology), as well as a collection of PresetRegion objects that define how the preset sounds.

You can access the metadata using the following getter methods:

• get_name(&self) -> &str: Returns the name of the preset.
• get_patch_number(&self) -> i32: Returns the patch number.
• get_bank_number(&self) -> i32: Returns the bank number.
• get_library(&self) -> i32: Returns the library information.
• get_genre(&self) -> i32: Returns the genre information.
• get_morphology(&self) -> i32: Returns the morphology information.
• get_regions(&self) -> &[PresetRegion]: Returns a slice of the regions associated with this preset.

// Example of accessing Preset metadata
let name = preset.get_name();
let patch = preset.get_patch_number();
let regions = preset.get_regions();