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|
use std::{
io::{self, Cursor},
sync::Arc,
time::Duration,
};
use async_channel::{Receiver, TryRecvError};
use bevy::{
asset::{io::Reader, AssetLoader, LoadContext},
audio::Source,
prelude::*,
tasks::AsyncComputeTaskPool,
};
use itertools::Itertools;
use rustysynth::{MidiFile, MidiFileSequencer, SoundFont, Synthesizer, SynthesizerSettings};
/// Represents a single MIDI note in a sequence
#[derive(Clone, Debug)]
pub struct MidiNote {
/// Channel to play the note on
pub channel: i32,
/// Preset (instrument) to play the note with (see GM spec.)
pub preset: i32,
/// Bank to play note with
pub bank: i32,
/// Key to play (60 is middle C)
pub key: i32,
/// Velocity to play note at
pub velocity: i32,
/// Duration to play note for
pub duration: Duration,
}
impl Default for MidiNote {
fn default() -> Self {
Self {
channel: 0,
preset: 0,
bank: 0,
key: 60,
velocity: 100,
duration: Duration::from_secs(1),
}
}
}
/// MIDI audio asset
#[derive(Asset, TypePath, Clone, Debug)]
pub enum MidiAudio {
/// Plays audio from a MIDI file
File(Vec<u8>),
/// Plays a simple sequence of notes
Sequence(Vec<MidiNote>),
}
/// AssetLoader for MIDI files (.mid/.midi)
#[derive(Default, Debug)]
pub struct MidiAssetLoader;
impl AssetLoader for MidiAssetLoader {
type Asset = MidiAudio;
type Settings = ();
type Error = io::Error;
async fn load(
&self,
reader: &mut dyn Reader,
_settings: &Self::Settings,
_load_context: &mut LoadContext<'_>,
) -> Result<Self::Asset, Self::Error> {
let mut bytes = vec![];
reader.read_to_end(&mut bytes).await?;
Ok(MidiAudio::File(bytes))
}
fn extensions(&self) -> &[&str] {
&["mid", "midi"]
}
}
/// Decoder for MIDI file playback
pub struct MidiFileDecoder {
sample_rate: usize,
stream: Receiver<f32>,
}
impl MidiFileDecoder {
/// Construct and begin a new MIDI sequencer with the given MIDI data and soundfont.
///
/// The sequencer will push at most 1 second's worth of audio ahead, allowing the decoder to
/// be paused without endlessly backing up data forever.
pub fn new(midi: MidiAudio, soundfont: Arc<SoundFont>) -> Self {
let sample_rate = 44100_usize;
let (tx, rx) = async_channel::bounded::<f32>(sample_rate * 2);
AsyncComputeTaskPool::get()
.spawn(async move {
let settings = SynthesizerSettings::new(sample_rate as i32);
let mut synthesizer =
Synthesizer::new(&soundfont, &settings).expect("Failed to create synthesizer.");
match midi {
MidiAudio::File(midi_data) => {
let mut sequencer = MidiFileSequencer::new(synthesizer);
let mut midi_data = Cursor::new(midi_data);
let midi = Arc::new(
MidiFile::new(&mut midi_data).expect("Failed to read midi file."),
);
sequencer.play(&midi, false);
let mut left: Vec<f32> = vec![0_f32; sample_rate];
let mut right: Vec<f32> = vec![0_f32; sample_rate];
while !sequencer.end_of_sequence() {
sequencer.render(&mut left, &mut right);
for value in left.iter().interleave(right.iter()) {
if let Err(_) = tx.send(*value).await {
return;
};
}
}
}
MidiAudio::Sequence(sequence) => {
for MidiNote {
channel,
preset,
bank,
key,
velocity,
duration,
} in sequence.iter()
{
synthesizer.process_midi_message(*channel, 0xB0, 0x00, *bank);
synthesizer.process_midi_message(*channel, 0xC0, *preset, 0);
synthesizer.note_on(*channel, *key, *velocity);
let note_length =
(sample_rate as f32 * duration.as_secs_f32()) as usize;
let mut left: Vec<f32> = vec![0_f32; note_length];
let mut right: Vec<f32> = vec![0_f32; note_length];
for (left, right) in left.chunks_mut(sample_rate).zip(right.chunks_mut(sample_rate)) {
synthesizer.render(left, right);
for value in left.iter().interleave(right.iter()) {
if let Err(_) = tx.send(*value).await {
return;
};
}
}
synthesizer.note_off(*channel, *key);
}
}
}
tx.close();
})
.detach();
Self {
sample_rate,
stream: rx,
}
}
}
impl Iterator for MidiFileDecoder {
type Item = f32;
fn next(&mut self) -> Option<Self::Item> {
match self.stream.try_recv() {
Ok(value) => Some(value),
Err(e) => match e {
TryRecvError::Empty => Some(0.0),
TryRecvError::Closed => None,
},
}
}
}
impl Source for MidiFileDecoder {
fn current_frame_len(&self) -> Option<usize> {
None
}
fn channels(&self) -> u16 {
2
}
fn sample_rate(&self) -> u32 {
self.sample_rate as u32
}
fn total_duration(&self) -> Option<std::time::Duration> {
None
}
}
impl Decodable for MidiAudio {
type Decoder = MidiFileDecoder;
type DecoderItem = <MidiFileDecoder as Iterator>::Item;
fn decoder(&self) -> Self::Decoder {
MidiFileDecoder::new(self.clone(), crate::SOUNDFONT.get().unwrap().clone())
}
}
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