From d630494d65129393645a414cf0ea1adbe9c401c4 Mon Sep 17 00:00:00 2001
From: Astatin <git@astatin.live>
Date: Tue, 22 Jul 2025 13:18:50 +0200
Subject: Make audio time accurate using audio buffers

---
 src/audio.rs         | 10 +++++++---
 src/desktop/audio.rs | 45 +++++++++++++++++++++++++++++++++++++++------
 src/io.rs            | 11 ++++++++++-
 3 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/src/audio.rs b/src/audio.rs
index b8f6aa9..427ca26 100644
--- a/src/audio.rs
+++ b/src/audio.rs
@@ -293,7 +293,7 @@ impl io::Wave for NoiseWave {
 }
 
 #[derive(Clone, Debug)]
-struct MutableWave {
+pub struct MutableWave {
     wave_ch1: Arc<Mutex<Option<Wave>>>,
     wave_ch2: Arc<Mutex<Option<Wave>>>,
     wave_ch3: Arc<Mutex<Option<Wave>>>,
@@ -583,7 +583,7 @@ impl AudioNoiseChannel {
 }
 
 pub struct Channels<A: Audio> {
-    _audio: A,
+    audio: A,
 
     pub ch1: AudioSquareChannel,
     pub ch2: AudioSquareChannel,
@@ -606,11 +606,15 @@ impl<A: Audio> Channels<A> {
         ));
 
         Self {
-            _audio: audio,
+            audio: audio,
             ch1: AudioSquareChannel::new(wave_ch1),
             ch2: AudioSquareChannel::new(wave_ch2),
             ch3: AudioCustomChannel::new(wave_ch3),
             ch4: AudioNoiseChannel::new(wave_ch4),
         }
     }
+
+    pub fn next(&mut self) {
+        self.audio.next();
+    }
 }
diff --git a/src/desktop/audio.rs b/src/desktop/audio.rs
index 2438d01..486b41c 100644
--- a/src/desktop/audio.rs
+++ b/src/desktop/audio.rs
@@ -1,12 +1,18 @@
 use rodio::{OutputStream, Sink, Source};
 
-use crate::audio::SAMPLE_RATE;
+use crate::audio::{SAMPLE_RATE, MutableWave};
 use crate::io::{Wave, Audio};
 use std::time::Duration;
+use std::mem;
+
+const BUFFER_SIZE: usize = 1024;
 
 pub struct RodioAudio {
     _stream: OutputStream,
-    _sink: Sink,
+    sink: Sink,
+    wave: RodioWave<MutableWave>,
+    buffer: Box<[f32; BUFFER_SIZE]>,
+    buffer_i: usize,
 }
 
 struct RodioWave<W: Wave + Send + 'static>(W, usize);
@@ -24,7 +30,17 @@ impl<W: Wave + Send + 'static> Iterator for RodioWave<W>
     }
 }
 
-impl<W: Wave + Send + 'static> Source for RodioWave<W>
+struct RodioBuffer<I: Iterator<Item = f32>>(I);
+
+impl<I: Iterator<Item = f32>> Iterator for RodioBuffer<I> {
+    type Item = f32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+}
+
+impl<I: Iterator<Item = f32>> Source for RodioBuffer<I>
 {
     fn current_frame_len(&self) -> Option<usize> {
         None
@@ -44,15 +60,32 @@ impl<W: Wave + Send + 'static> Source for RodioWave<W>
 }
 
 impl Audio for RodioAudio {
-    fn new<S: Wave + Send + 'static>(wave: S) -> Self {
+    fn new(wave: MutableWave) -> Self {
         let (stream, stream_handle) = OutputStream::try_default().unwrap();
 
         let sink = Sink::try_new(&stream_handle).unwrap();
-        sink.append(RodioWave(wave, 0));
+        let wave = RodioWave(wave, 0);
 
         RodioAudio {
             _stream: stream,
-            _sink: sink,
+            sink: sink,
+            wave,
+            buffer: Box::new([0.0; BUFFER_SIZE]),
+            buffer_i: 0,
+        }
+    }
+
+    fn next(&mut self) {
+        if let Some(v) = self.wave.next() {
+            self.buffer[self.buffer_i] = v;
+            self.buffer_i += 1;
+
+            if self.buffer_i == BUFFER_SIZE {
+                self.buffer_i = 0;
+                let mut buffer = Box::new([0.0; BUFFER_SIZE]);
+                mem::swap(&mut self.buffer, &mut buffer);
+                self.sink.append(RodioBuffer(buffer.into_iter()));
+            }
         }
     }
 }
diff --git a/src/io.rs b/src/io.rs
index 92e5984..06775a2 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -1,6 +1,7 @@
 use std::time::SystemTime;
 use std::{thread, time};
 
+use crate::audio::MutableWave;
 use crate::consts;
 use crate::state::GBState;
 
@@ -65,7 +66,8 @@ pub trait Wave {
 }
 
 pub trait Audio {
-    fn new<S: Wave + Send + 'static>(wave: S) -> Self;
+    fn new(wave: MutableWave) -> Self;
+    fn next(&mut self);
 }
 
 pub trait LoadSave
@@ -147,6 +149,7 @@ impl<I: Input, W: Window, S: Serial, A: Audio, LS: LoadSave> Gameboy<I, W, S, A,
         let mut total_cycle_counter: u128 = 0;
         let mut nanos_sleep: f64 = 0.0;
         let mut halt_time = 0;
+        let mut audio_counter = 0;
         let mut was_previously_halted = false;
 
         let mut last_ram_bank_enabled = false;
@@ -168,6 +171,12 @@ impl<I: Input, W: Window, S: Serial, A: Audio, LS: LoadSave> Gameboy<I, W, S, A,
 
             state.cpu.dbg_cycle_counter += c;
             total_cycle_counter += c as u128;
+            audio_counter += c;
+
+            if audio_counter >= 32 {
+                audio_counter -= 32;
+                state.mem.audio.next();
+            }
 
             state.div_timer(c);
             state.tima_timer(c);
-- 
cgit v1.2.3-70-g09d2