P0: Rust engine, wire daemon and audio-reactive descent surface
This commit is contained in:
Emil
@@ -0,0 +1,538 @@
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//! ZHILA audio engine, P0.
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//!
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//! A real cpal stream with a fixed voice pool, a two-bar phrase, per-vein
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//! levels and a bar position. Everything that runs in the callback is
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//! allocation-free. The control surface is lock-free on the audio side.
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use std::f32::consts::{FRAC_PI_4, TAU};
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use std::sync::atomic::{AtomicU32, Ordering};
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use std::sync::{Arc, Mutex};
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use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
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use cpal::{BufferSize, FromSample, SampleFormat, SizedSample, Stream, StreamConfig};
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use rtrb::{Consumer, Producer, RingBuffer};
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use thiserror::Error;
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use zhila_core::Engine as EngineControl;
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use zhila_protocol::{
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AudioInfo, LOOP_STEPS, MAX_BPM, MAX_GAIN, MIN_BPM, MIN_GAIN, MeterFrame, Pattern,
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STEPS_PER_BAR, VEIN_COUNT, VeinId,
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};
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const VOICES: usize = 32;
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#[derive(Debug, Clone, Copy)]
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enum AudioCommand {
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Play,
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Stop,
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Strike { vein: u8, velocity: f32 },
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SetTempo(f32),
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SetGain { vein: u8, gain: f32 },
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}
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struct Levels {
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master: AtomicU32,
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veins: [AtomicU32; VEIN_COUNT],
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bar: AtomicU32,
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}
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impl Levels {
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fn new() -> Self {
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Self {
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master: AtomicU32::new(0.0f32.to_bits()),
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veins: std::array::from_fn(|_| AtomicU32::new(0.0f32.to_bits())),
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bar: AtomicU32::new(1.0f32.to_bits()),
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}
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}
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fn store(&self, frame: &MeterFrame) {
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self.master.store(frame.master.to_bits(), Ordering::Relaxed);
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self.bar.store(frame.bar.to_bits(), Ordering::Relaxed);
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for (level, slot) in frame.veins.iter().zip(self.veins.iter()) {
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slot.store(level.to_bits(), Ordering::Relaxed);
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}
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}
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fn load(&self) -> MeterFrame {
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let master = f32::from_bits(self.master.load(Ordering::Relaxed));
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let bar = f32::from_bits(self.bar.load(Ordering::Relaxed));
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let mut veins = [0.0; VEIN_COUNT];
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for (level, slot) in veins.iter_mut().zip(self.veins.iter()) {
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*level = f32::from_bits(slot.load(Ordering::Relaxed));
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}
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MeterFrame { bar, master, veins }
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}
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}
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struct Voice {
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active: bool,
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vein: usize,
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phase: f32,
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freq: f32,
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t: f32,
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attack: f32,
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decay: f32,
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velocity: f32,
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gain_l: f32,
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gain_r: f32,
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lp: f32,
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hp: f32,
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prev: f32,
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rng: u32,
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}
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impl Voice {
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fn inactive() -> Self {
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Self {
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active: false,
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vein: 0,
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phase: 0.0,
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freq: 0.0,
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t: 0.0,
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attack: 0.01,
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decay: 4.0,
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velocity: 0.0,
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gain_l: 0.707,
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gain_r: 0.707,
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lp: 0.0,
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hp: 0.0,
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prev: 0.0,
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rng: 0x9e37_79b9,
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}
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}
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fn trigger(&mut self, vein: VeinId, velocity: f32, seed: u32) {
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self.active = true;
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self.vein = vein.index();
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self.phase = 0.0;
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self.t = 0.0;
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self.velocity = velocity.clamp(0.0, 1.0);
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self.rng = seed | 1;
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self.lp = 0.0;
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self.hp = 0.0;
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self.prev = 0.0;
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let (freq, attack, decay, pan) = match vein {
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VeinId::Bass => (55.0, 0.004, 3.2, 0.0),
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VeinId::Crack => (0.0, 0.001, 38.0, 0.35),
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VeinId::Voice => (220.0, 0.09, 1.1, -0.25),
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VeinId::Noise => (0.0, 0.004, 5.0, 0.55),
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VeinId::Silt => (1318.5, 0.002, 14.0, -0.45),
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};
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self.freq = freq;
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self.attack = attack;
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self.decay = decay;
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let angle = (pan + 1.0) * FRAC_PI_4;
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self.gain_l = angle.cos();
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self.gain_r = angle.sin();
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}
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fn noise(&mut self) -> f32 {
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self.rng = self.rng.wrapping_mul(1_664_525).wrapping_add(1_013_904_223);
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(self.rng as f32 / u32::MAX as f32) * 2.0 - 1.0
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}
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fn next(&mut self, sample_rate: f32) -> f32 {
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self.t += 1.0 / sample_rate;
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let attack = (self.t / self.attack).min(1.0);
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let env = attack * (-self.t * self.decay).exp();
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if env < 0.0002 || self.t > 8.0 {
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self.active = false;
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return 0.0;
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}
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let sample = match self.vein {
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0 => {
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let fundamental = (TAU * self.phase).sin();
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let sub = (TAU * self.phase * 0.5).sin();
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fundamental + sub * 0.45
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}
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1 => {
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let white = self.noise();
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let hp = white - self.prev + 0.94 * self.hp;
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self.prev = white;
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self.hp = hp;
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hp * 0.7
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}
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2 => {
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let fundamental = (TAU * self.phase).sin();
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let overtone = (TAU * self.phase * 2.0).sin();
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fundamental + overtone * 0.18
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}
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3 => {
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let white = self.noise();
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self.lp += (white - self.lp) * 0.06;
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self.lp
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}
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_ => (TAU * self.phase).sin(),
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};
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if self.freq > 0.0 {
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self.phase += self.freq / sample_rate;
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if self.phase >= 1.0 {
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self.phase -= 1.0;
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}
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}
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sample * env * self.velocity
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}
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}
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struct AudioState {
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rx: Consumer<AudioCommand>,
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sample_rate: f32,
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channels: usize,
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bpm: f32,
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playing: bool,
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step: usize,
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pending: f64,
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pattern: [[u8; LOOP_STEPS]; VEIN_COUNT],
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voices: [Voice; VOICES],
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gains: [f32; VEIN_COUNT],
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master_env: f32,
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vein_env: [f32; VEIN_COUNT],
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bar: f32,
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rng: u32,
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}
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impl AudioState {
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fn new(sample_rate: u32, channels: u16, pattern: &Pattern, rx: Consumer<AudioCommand>) -> Self {
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let mut grid = [[0u8; LOOP_STEPS]; VEIN_COUNT];
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for row in &pattern.rows {
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let index = row.vein.index();
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for (step, velocity) in row.velocities.iter().take(LOOP_STEPS).enumerate() {
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grid[index][step] = *velocity;
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}
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}
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Self {
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rx,
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sample_rate: sample_rate as f32,
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channels: channels as usize,
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bpm: 128.0,
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playing: false,
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step: 0,
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pending: 0.0,
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pattern: grid,
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voices: std::array::from_fn(|_| Voice::inactive()),
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gains: zhila_core::INITIAL_GAINS,
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master_env: 0.0,
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vein_env: [0.0; VEIN_COUNT],
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bar: 1.0,
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rng: 0x51ed_2701,
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}
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}
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fn step_samples(&self) -> f64 {
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self.sample_rate as f64 * 60.0 / self.bpm as f64 / 2.0
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}
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fn handle(&mut self, command: AudioCommand) {
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match command {
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AudioCommand::Play => {
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self.playing = true;
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self.step = 0;
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self.pending = 0.0;
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self.bar = 1.0;
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}
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AudioCommand::Stop => {
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self.playing = false;
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self.step = 0;
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self.pending = 0.0;
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self.bar = 1.0;
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self.master_env = 0.0;
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self.vein_env = [0.0; VEIN_COUNT];
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for voice in &mut self.voices {
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voice.active = false;
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}
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}
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AudioCommand::Strike { vein, velocity } => {
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let Some(vein) = VeinId::from_index(vein as usize) else {
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return;
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};
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self.trigger(vein, velocity);
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}
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AudioCommand::SetTempo(bpm) => {
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self.bpm = bpm.clamp(MIN_BPM, MAX_BPM);
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}
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AudioCommand::SetGain { vein, gain } => {
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if let Some(index) = VeinId::from_index(vein as usize) {
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self.gains[index.index()] = gain.clamp(MIN_GAIN, MAX_GAIN);
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}
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}
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}
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}
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fn trigger(&mut self, vein: VeinId, velocity: f32) {
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if velocity <= 0.0 {
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return;
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}
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let index = self
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.voices
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.iter()
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.position(|voice| !voice.active)
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.unwrap_or_else(|| {
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self.voices
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.iter()
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.enumerate()
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.max_by(|a, b| a.1.t.total_cmp(&b.1.t))
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.map(|(index, _)| index)
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.unwrap_or(0)
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});
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self.rng = self.rng.wrapping_mul(1_664_525).wrapping_add(1_013_904_223);
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self.voices[index].trigger(vein, velocity, self.rng);
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}
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fn trigger_step(&mut self) {
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let step = self.step;
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for vein in 0..VEIN_COUNT {
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let velocity = self.pattern[vein][step];
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if velocity > 0
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&& let Some(vein) = VeinId::from_index(vein)
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{
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self.trigger(vein, velocity as f32 / 127.0);
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}
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}
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self.bar = step as f32 / STEPS_PER_BAR as f32 + 1.0;
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self.step = (step + 1) % LOOP_STEPS;
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}
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fn render<T>(&mut self, data: &mut [T], levels: &Levels)
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where
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T: SizedSample + FromSample<f32>,
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{
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while let Ok(command) = self.rx.pop() {
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self.handle(command);
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}
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for frame in data.chunks_mut(self.channels) {
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if self.playing {
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if self.pending <= 0.0 {
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self.trigger_step();
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self.pending += self.step_samples();
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}
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self.pending -= 1.0;
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}
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let mut left = 0.0f32;
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let mut right = 0.0f32;
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let mut sums = [0.0f32; VEIN_COUNT];
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for voice in &mut self.voices {
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if !voice.active {
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continue;
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}
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let sample = voice.next(self.sample_rate);
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let index = voice.vein;
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let amplitude = sample * self.gains[index];
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left += amplitude * voice.gain_l;
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right += amplitude * voice.gain_r;
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sums[index] += amplitude.abs();
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}
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let peak = (left.abs() + right.abs()) * 0.5;
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self.master_env += (peak - self.master_env) * 0.0015;
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for (env, sum) in self.vein_env.iter_mut().zip(sums.iter()) {
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*env += (*sum - *env) * 0.002;
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}
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let out_l = (left * 0.9).tanh() * 0.8;
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let out_r = (right * 0.9).tanh() * 0.8;
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for (channel, sample) in frame.iter_mut().enumerate() {
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let value = match (self.channels, channel) {
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(1, _) => (out_l + out_r) * 0.5,
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(_, 0) => out_l,
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(_, 1) => out_r,
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_ => (out_l + out_r) * 0.5,
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};
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*sample = T::from_sample(value);
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}
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}
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levels.store(&MeterFrame {
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bar: self.bar,
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master: self.master_env,
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veins: self.vein_env,
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});
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}
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}
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/// The send side of the engine. Cheap, lock-free for the audio thread and
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/// safe to share with the session and the WebSocket daemon.
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pub struct Control {
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tx: Mutex<Producer<AudioCommand>>,
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levels: Arc<Levels>,
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info: AudioInfo,
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}
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impl EngineControl for Control {
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fn play(&self) {
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self.send(AudioCommand::Play);
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}
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fn stop(&self) {
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self.send(AudioCommand::Stop);
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}
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fn strike(&self, vein: VeinId, velocity: f32) {
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self.send(AudioCommand::Strike {
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vein: vein.index() as u8,
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velocity,
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});
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}
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fn set_tempo(&self, bpm: f32) {
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self.send(AudioCommand::SetTempo(bpm));
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}
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fn set_gain(&self, vein: VeinId, gain: f32) {
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self.send(AudioCommand::SetGain {
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vein: vein.index() as u8,
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gain,
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});
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}
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fn info(&self) -> AudioInfo {
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self.info.clone()
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}
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fn meter(&self) -> MeterFrame {
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self.levels.load()
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}
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}
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impl Control {
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fn send(&self, command: AudioCommand) {
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if let Ok(mut tx) = self.tx.lock() {
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let _ = tx.push(command);
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}
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}
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}
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#[derive(Debug, Error)]
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pub enum EngineError {
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#[error("no default audio output device")]
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NoDevice,
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#[error("audio backend: {0}")]
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Backend(#[from] cpal::Error),
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#[error("unsupported sample format: {0:?}")]
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UnsupportedFormat(SampleFormat),
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}
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struct Started {
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stream: Stream,
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control: Arc<Control>,
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}
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/// Keeps the cpal stream alive. The control handle can be shared freely; the
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/// stream itself must stay on the thread that created it.
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pub struct AudioEngine {
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_stream: Stream,
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control: Arc<Control>,
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}
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impl AudioEngine {
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pub fn start(pattern: &Pattern) -> Result<Self, EngineError> {
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let started = match Self::try_start(pattern, BufferSize::Fixed(256)) {
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Ok(started) => started,
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Err(EngineError::Backend(_)) => Self::try_start(pattern, BufferSize::Default)?,
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Err(error) => return Err(error),
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};
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Ok(Self {
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_stream: started.stream,
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control: started.control,
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})
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}
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pub fn control(&self) -> Arc<Control> {
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self.control.clone()
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}
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pub fn info(&self) -> AudioInfo {
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self.control.info.clone()
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}
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fn try_start(pattern: &Pattern, buffer: BufferSize) -> Result<Started, EngineError> {
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let host = cpal::default_host();
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let device = host.default_output_device().ok_or(EngineError::NoDevice)?;
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let supported = device.default_output_config()?;
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let format = supported.sample_format();
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let mut config: StreamConfig = supported.into();
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config.buffer_size = buffer;
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let sample_rate = config.sample_rate;
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let channels = config.channels;
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let device_name = device.to_string();
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let (producer, consumer) = RingBuffer::new(256);
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let levels = Arc::new(Levels::new());
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let state = AudioState::new(sample_rate, channels, pattern, consumer);
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let stream = match format {
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SampleFormat::F32 => build_stream::<f32>(&device, config, state, levels.clone())?,
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SampleFormat::I16 => build_stream::<i16>(&device, config, state, levels.clone())?,
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other => return Err(EngineError::UnsupportedFormat(other)),
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};
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let info = AudioInfo {
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running: true,
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device: device_name,
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sample_rate,
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buffer_frames: match buffer {
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BufferSize::Fixed(frames) => frames,
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BufferSize::Default => 0,
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},
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channels,
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};
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let control = Arc::new(Control {
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tx: Mutex::new(producer),
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levels,
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info,
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});
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Ok(Started { stream, control })
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}
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}
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||||
fn build_stream<T>(
|
||||
device: &cpal::Device,
|
||||
config: StreamConfig,
|
||||
mut state: AudioState,
|
||||
levels: Arc<Levels>,
|
||||
) -> Result<Stream, EngineError>
|
||||
where
|
||||
T: SizedSample + FromSample<f32> + 'static,
|
||||
{
|
||||
let stream = device.build_output_stream(
|
||||
config,
|
||||
move |data: &mut [T], _: &cpal::OutputCallbackInfo| {
|
||||
state.render(data, &levels);
|
||||
},
|
||||
|error| eprintln!("zhila audio: {error}"),
|
||||
None,
|
||||
)?;
|
||||
stream.play()?;
|
||||
Ok(stream)
|
||||
}
|
||||
|
||||
/// A silent engine for headless protocol tests and machines without an output
|
||||
/// device. It reports itself as offline so the surface never pretends to play.
|
||||
pub struct NullEngine {
|
||||
info: AudioInfo,
|
||||
}
|
||||
|
||||
impl Default for NullEngine {
|
||||
fn default() -> Self {
|
||||
Self::new()
|
||||
}
|
||||
}
|
||||
|
||||
impl NullEngine {
|
||||
pub fn new() -> Self {
|
||||
Self {
|
||||
info: AudioInfo::offline(),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl EngineControl for NullEngine {
|
||||
fn play(&self) {}
|
||||
fn stop(&self) {}
|
||||
fn strike(&self, _vein: VeinId, _velocity: f32) {}
|
||||
fn set_tempo(&self, _bpm: f32) {}
|
||||
fn set_gain(&self, _vein: VeinId, _gain: f32) {}
|
||||
fn info(&self) -> AudioInfo {
|
||||
self.info.clone()
|
||||
}
|
||||
fn meter(&self) -> MeterFrame {
|
||||
MeterFrame::silent()
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user