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|
use std::{
io::{self, Cursor},
sync::Arc,
};
use async_channel::{Receiver, TryRecvError};
use bevy::{
asset::{io::Reader, AssetLoader, AsyncReadExt, LoadContext},
audio::Source,
prelude::*,
tasks::AsyncComputeTaskPool,
};
use itertools::Itertools;
use rustysynth::{MidiFile, MidiFileSequencer, SoundFont, Synthesizer, SynthesizerSettings};
/// MIDI audio asset
#[derive(Asset, TypePath)]
pub struct MidiAudio {
/// MIDI file data
pub midi: Vec<u8>,
}
/// 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<'a>(
&'a self,
reader: &'a mut Reader<'_>,
_settings: &'a Self::Settings,
_load_context: &'a mut LoadContext<'_>,
) -> Result<Self::Asset, Self::Error> {
let mut bytes = vec![];
reader.read_to_end(&mut bytes).await?;
Ok(MidiAudio { midi: bytes })
}
}
/// Decoder for MIDI file playback
pub struct MidiDecoder {
sample_rate: usize,
stream: Receiver<f32>,
}
impl MidiDecoder {
/// 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: Vec<u8>, soundfont: Arc<SoundFont>) -> Self {
let mut midi = Cursor::new(midi);
let sample_rate = 44100_usize;
let (tx, rx) = async_channel::bounded::<f32>(sample_rate * 2);
AsyncComputeTaskPool::get()
.spawn(async move {
let midi = Arc::new(MidiFile::new(&mut midi).expect("Failed to read midi file."));
let settings = SynthesizerSettings::new(sample_rate as i32);
let synthesizer =
Synthesizer::new(&soundfont, &settings).expect("Failed to create synthesizer.");
let mut sequencer = MidiFileSequencer::new(synthesizer);
sequencer.play(&midi, true);
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(e) = tx.send(*value).await {
error!("{e}");
};
}
}
tx.close();
})
.detach();
Self {
sample_rate,
stream: rx,
}
}
}
impl Iterator for MidiDecoder {
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 MidiDecoder {
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 = MidiDecoder;
type DecoderItem = <MidiDecoder as Iterator>::Item;
fn decoder(&self) -> Self::Decoder {
MidiDecoder::new(self.midi.clone(), crate::SOUNDFONT.get().unwrap().clone())
}
}
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