bbx_midi

MIDI message parsing and streaming utilities for audio applications.

Features

• MIDI message parsing: Parse raw MIDI bytes into structured messages
• Message type helpers: Extract note, velocity, pitch wheel, control data
• Lock-free buffer: Thread-safe SPSC ring buffer for MIDI-to-audio communication
• Input streaming: Real-time MIDI input via midir
• FFI compatible: #[repr(C)] types for C interop

Message Types

• NoteOn / NoteOff - Note events with velocity
• ControlChange - CC messages (mod wheel, sustain, etc.)
• PitchWheel - Pitch bend with 14-bit resolution
• ProgramChange - Instrument/patch changes
• PolyphonicAftertouch - Per-note pressure
• ChannelAftertouch - Channel-wide pressure

MidiEvent

For sample-accurate MIDI timing in audio callbacks:

use bbx_midi::{MidiMessage, MidiEvent};

let event = MidiEvent {
    message: MidiMessage::new([0x90, 60, 100]),
    sample_offset: 128,  // Process at sample 128 in buffer
};

Used with PluginDsp::process() for synthesizer plugins.

Usage

use bbx_midi::{MidiMessage, MidiMessageStatus};

// Parse raw MIDI bytes
let msg = MidiMessage::new([0x90, 60, 100]); // Note On, C4, velocity 100

if msg.get_status() == MidiMessageStatus::NoteOn {
    println!("Note: {}", msg.get_note().unwrap());          // "C4"
    println!("Frequency: {} Hz", msg.get_note_frequency().unwrap()); // ~261.6
    println!("Velocity: {}", msg.get_velocity().unwrap());   // 100
}

Lock-Free MIDI Buffer

For thread-safe communication between MIDI and audio threads:

use bbx_midi::{midi_buffer, MidiMessage};

// Create producer/consumer pair
let (mut producer, mut consumer) = midi_buffer(64);

// MIDI thread: push messages
let msg = MidiMessage::new([0x90, 60, 100]);
producer.try_send(msg);

// Audio thread: pop messages (realtime-safe)
while let Some(msg) = consumer.try_pop() {
    // Process MIDI message
}

The buffer uses an SPSC ring buffer internally, making all consumer operations lock-free and allocation-free for real-time safety.

Cargo Features

streaming

Enables real-time MIDI input via midir:

[dependencies]
bbx_midi = { version = "...", features = ["streaming"] }

use bbx_midi::{stream::MidiInputStream, MidiMessage, MidiMessageStatus};

// Create stream with optional filters
let stream = MidiInputStream::new(
    vec![MidiMessageStatus::NoteOn, MidiMessageStatus::NoteOff],
    |msg| println!("Received: {:?}", msg),
);

// Start listening (prompts for port selection)
let handle = stream.init();

Used by bbx_sandbox for terminal-based DSP testing with live MIDI input.

License

MIT