sdl2: Use callbacks with ring buffer instead of audio queue.

Better latencies, and also fast-forward (aka Turbo mode) sounds normal
this way.


Former-commit-id: d1075087e847c765a871157a7973c897575ef4d7

Cargo.lock

@@ -212,6 +212,15 @@ dependencies = [
  "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "debug_stub_derive"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "dirs"
 version = "2.0.2"
@@ -669,6 +678,11 @@ name = "rgb"
 version = "0.8.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "ringbuf"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "rustboyadvance-ng"
 version = "0.1.0"
@@ -682,12 +696,14 @@ dependencies = [
  "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "colored 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ctrlc 3.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "debug_stub_derive 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "enum-primitive-derive 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "hexdump 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "minifb 0.11.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "nom 5.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "num 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ringbuf 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustyline 5.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sdl2 0.32.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "spin_sleep 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1007,6 +1023,7 @@ dependencies = [
 "checksum constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8ff012e225ce166d4422e0e78419d901719760f62ae2b7969ca6b564d1b54a9e"
 "checksum crc32fast 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ba125de2af0df55319f41944744ad91c71113bf74a4646efff39afe1f6842db1"
 "checksum ctrlc 3.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c7dfd2d8b4c82121dfdff120f818e09fc4380b0b7e17a742081a89b94853e87f"
+"checksum debug_stub_derive 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "496b7f8a2f853313c3ca370641d7ff3e42c32974fdccda8f0684599ed0a3ff6b"
 "checksum dirs 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "13aea89a5c93364a98e9b37b2fa237effbb694d5cfe01c5b70941f7eb087d5e3"
 "checksum dirs-sys 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "afa0b23de8fd801745c471deffa6e12d248f962c9fd4b4c33787b055599bde7b"
 "checksum enum-primitive-derive 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e2b90e520ec62c1864c8c78d637acbfe8baf5f63240f2fb8165b8325c07812dd"
@@ -1060,6 +1077,7 @@ dependencies = [
 "checksum redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)" = "2439c63f3f6139d1b57529d16bc3b8bb855230c8efcc5d3a896c8bea7c3b1e84"
 "checksum redox_users 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3fe5204c3a17e97dde73f285d49be585df59ed84b50a872baf416e73b62c3828"
 "checksum rgb 0.8.13 (registry+https://github.com/rust-lang/crates.io-index)" = "4f089652ca87f5a82a62935ec6172a534066c7b97be003cc8f702ee9a7a59c92"
+"checksum ringbuf 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7c2b29d87cfbdce39849012bb5020fff88b8f01f4f5b55846a0b6ef360774eae"
 "checksum rustc-demangle 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)" = "a7f4dccf6f4891ebcc0c39f9b6eb1a83b9bf5d747cb439ec6fba4f3b977038af"
 "checksum rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
 "checksum rustyline 5.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "67e12e40e0240de07f0dab4f4dd01bdb15d74dc977026d4ba91666c41c679ade"

Cargo.toml

@@ -26,6 +26,8 @@ zip = "0.5.3"
 ctrlc = "3.1.3"
 spin_sleep="0.3.7"
 bit-set = "0.5.1"
+ringbuf = "0.2.1"
+debug_stub_derive = "0.3.0"
 
 [[bin]]
 name = "rba-sdl2"

src/core/gpu/mod.rs

@@ -467,12 +467,7 @@ impl Gpu {
     }
 
     // Returns the new gpu state
-    pub fn step(
+    pub fn step(&mut self, cycles: usize, sb: &mut SysBus, irqs: &mut IrqBitmask) {
-        &mut self,
-        cycles: usize,
-        sb: &mut SysBus,
-        irqs: &mut IrqBitmask,
-    ) {
         self.cycles += cycles;
 
         match self.state {

src/core/sound/dsp.rs

@@ -1,37 +1,34 @@
-pub type Sample = (i16, i16);
+use crate::{AudioInterface, StereoSample};
+
 const PI: f32 = std::f32::consts::PI;
 
 pub trait Resampler {
-    fn push_sample(&mut self, s: Sample, output: &mut Vec<i16>);
+    fn push_sample(&mut self, s: StereoSample, audio: &mut dyn AudioInterface);
 }
 
+#[derive(Debug)]
 pub struct CosineResampler {
-    last_in_sample: Sample,
+    last_in_sample: StereoSample,
     phase: f32,
     pub in_freq: f32,
     out_freq: f32,
 }
 
-fn cosine_interpolation(y1: Sample, y2: Sample, phase: f32) -> Sample {
+fn cosine_interpolation(y1: i16, y2: i16, phase: f32) -> i16 {
-    let y1_left = y1.0 as f32;
+    let y1 = y1 as i32 as f32;
-    let y1_right = y1.1 as f32;
+    let y2 = y2 as i32 as f32;
-    let y2_left = y2.0 as f32;
-    let y2_right = y2.1 as f32;
 
     let mu2 = (1.0 - (PI * phase).cos()) / 2.0;
 
-    (
+    (y2 * (1.0 - mu2) + y1 * mu2) as i16
-        (y2_left * (1.0 - mu2) + y1_left * mu2) as i16,
-        (y2_right * (1.0 - mu2) + y1_right * mu2) as i16,
-    )
 }
 
 impl Resampler for CosineResampler {
-    fn push_sample(&mut self, s: Sample, output: &mut Vec<i16>) {
+    fn push_sample(&mut self, s: StereoSample, audio: &mut dyn AudioInterface) {
         while self.phase < 1.0 {
-            let x = cosine_interpolation(self.last_in_sample, s, self.phase);
+            let left = cosine_interpolation(self.last_in_sample.0, s.0, self.phase);
-            output.push(x.0);
+            let right = cosine_interpolation(self.last_in_sample.1, s.1, self.phase);
-            output.push(x.1);
+            audio.push_sample((left, right));
             self.phase += self.in_freq / self.out_freq;
         }
         self.phase = self.phase - 1.0;

src/core/sound/fifo.rs

@@ -1,5 +1,4 @@
 // TODO write tests or replace with a crate
-
 const SOUND_FIFO_CAPACITY: usize = 32;
 
 #[derive(Debug)]

src/core/sound/mod.rs

@@ -31,10 +31,20 @@ struct DmaSoundChannel {
     fifo: SoundFifo,
 }
 
+impl DmaSoundChannel {
+    fn is_stereo_channel_enabled(&self, channel: usize) -> bool {
+        match channel {
+            0 => self.enable_left,
+            1 => self.enable_right,
+            _ => unreachable!(),
+        }
+    }
+}
+
 impl Default for DmaSoundChannel {
     fn default() -> DmaSoundChannel {
         DmaSoundChannel {
-            volume_shift: 1,
+            volume_shift: 0,
             value: 0,
             enable_right: false,
             enable_left: false,
@@ -50,8 +60,12 @@ const REG_FIFO_A_H: u32 = REG_FIFO_A + 2;
 const REG_FIFO_B_L: u32 = REG_FIFO_B;
 const REG_FIFO_B_H: u32 = REG_FIFO_B + 2;
 
+type AudioDeviceRcRefCell = Rc<RefCell<dyn AudioInterface>>;
+
+#[derive(DebugStub)]
 pub struct SoundController {
-    audio_device: Rc<RefCell<dyn AudioInterface>>,
+    #[debug_stub = "AudioDeviceRcRefCell"]
+    audio_device: AudioDeviceRcRefCell,
 
     sample_rate_to_cpu_freq: usize, // how many "cycles" are a sample?
     last_sample_cycles: usize,      // cycles count when we last provided a new sample.
@@ -90,7 +104,7 @@ pub struct SoundController {
 }
 
 impl SoundController {
-    pub fn new(audio_device: Rc<RefCell<dyn AudioInterface>>) -> SoundController {
+    pub fn new(audio_device: AudioDeviceRcRefCell) -> SoundController {
         let resampler =
             CosineResampler::new(32768_f32, audio_device.borrow().get_sample_rate() as f32);
         SoundController {
@@ -250,13 +264,13 @@ impl SoundController {
             }
 
             REG_FIFO_A_L | REG_FIFO_A_H => {
-                self.dma_sound[0].fifo.write(((value >> 8) & 0xff) as i8);
                 self.dma_sound[0].fifo.write((value & 0xff) as i8);
+                self.dma_sound[0].fifo.write(((value >> 8) & 0xff) as i8);
             }
 
             REG_FIFO_B_L | REG_FIFO_B_H => {
-                self.dma_sound[1].fifo.write(((value >> 8) & 0xff) as i8);
                 self.dma_sound[1].fifo.write((value & 0xff) as i8);
+                self.dma_sound[1].fifo.write(((value >> 8) & 0xff) as i8);
             }
 
             REG_SOUNDBIAS => self.sound_bias = value & 0xc3fe,
@@ -283,11 +297,11 @@ impl SoundController {
 
         const FIFO_INDEX_TO_REG: [u32; 2] = [REG_FIFO_A, REG_FIFO_B];
         for fifo in 0..2 {
-            let channel = &mut self.dma_sound[fifo];
+            let dma = &mut self.dma_sound[fifo];
 
-            if timer_id == channel.timer_select {
+            if timer_id == dma.timer_select {
-                channel.value = channel.fifo.read();
+                dma.value = dma.fifo.read();
-                if channel.fifo.count() <= 16 {
+                if dma.fifo.count() <= 16 {
                     dmac.notify_sound_fifo(FIFO_INDEX_TO_REG[fifo]);
                 }
             }
@@ -310,22 +324,19 @@ impl SoundController {
 
             // time to push a new sample!
 
-            let mut sample = (0i16, 0i16);
+            let mut sample = [0; 2];
-            for i in 0..2 {
+
-                let channel = &self.dma_sound[i];
+            for channel in 0..=1 {
-                if channel.enable_left {
+                for dma in &mut self.dma_sound {
-                    sample.0 += ((channel.value as i16) << 8) >> channel.volume_shift;
+                    if dma.is_stereo_channel_enabled(channel) {
-                }
+                        sample[channel] += dma.value as i16;
-                if channel.enable_right {
+                    }
-                    sample.1 += ((channel.value as i16) << 8) >> channel.volume_shift;
                 }
             }
 
-            self.resampler.push_sample(sample, &mut self.output_buffer);
+            let mut audio = self.audio_device.borrow_mut();
-            if self.output_buffer.len() >= 10000 {
+            self.resampler
-                self.audio_device.borrow_mut().play(&self.output_buffer);
+                .push_sample((sample[0], sample[1]), &mut *audio);
-                self.output_buffer.clear();
-            }
         }
     }
 }

src/lib.rs

@@ -2,6 +2,9 @@
 #![feature(core_intrinsics)]
 #![feature(exclusive_range_pattern)]
 
+#[macro_use]
+extern crate debug_stub_derive;
+
 #[macro_use]
 extern crate enum_primitive_derive;
 extern crate num;
@@ -34,11 +37,13 @@ pub trait VideoInterface {
     fn render(&mut self, buffer: &[u32]);
 }
 
+pub type StereoSample = (i16, i16);
+
 pub trait AudioInterface {
     fn get_sample_rate(&self) -> i32;
 
     #[allow(unused_variables)]
-    fn play(&mut self, samples: &[i16]) {}
+    fn push_sample(&mut self, samples: StereoSample) {}
 }
 
 pub trait InputInterface {

src/plat/sdl2/audio.rs

@@ -1,40 +1,89 @@
 use sdl2;
-use sdl2::audio::{AudioQueue, AudioSpecDesired};
+use sdl2::audio::{AudioCallback, AudioDevice, AudioSpec, AudioSpecDesired};
 
-use rustboyadvance_ng::AudioInterface;
+use rustboyadvance_ng::{AudioInterface, StereoSample};
+
+extern crate ringbuf;
+use ringbuf::{Consumer, Producer, RingBuffer};
+
+struct GbaAudioCallback {
+    consumer: Consumer<StereoSample>,
+    spec: AudioSpec,
+}
 
 pub struct Sdl2AudioPlayer {
-    pub device: AudioQueue<i16>,
+    _device: AudioDevice<GbaAudioCallback>,
+    producer: Producer<StereoSample>,
     freq: i32,
 }
 
+impl AudioCallback for GbaAudioCallback {
+    type Channel = i16;
+
+    fn callback(&mut self, out_samples: &mut [i16]) {
+        let sample_count = out_samples.len() / 2;
+
+        for i in 0..sample_count {
+            if let Some((left, right)) = self.consumer.pop() {
+                out_samples[2 * i] = left * (1 << 4);
+                out_samples[2 * i + 1] = right * (1 << 4);
+            } else {
+                out_samples[2 * i] = self.spec.silence as i16;
+                out_samples[2 * i + 1] = self.spec.silence as i16;
+            }
+        }
+    }
+}
+
 impl AudioInterface for Sdl2AudioPlayer {
     fn get_sample_rate(&self) -> i32 {
         self.freq
     }
 
-    fn play(&mut self, samples: &[i16]) {
+    fn push_sample(&mut self, sample: StereoSample) {
-        self.device.queue(&samples);
+        #![allow(unused_must_use)]
+        self.producer.push(sample);
     }
 }
 
 pub fn create_audio_player(sdl: &sdl2::Sdl) -> Sdl2AudioPlayer {
-    let audio_subsystem = sdl.audio().unwrap();
-
     let desired_spec = AudioSpecDesired {
         freq: Some(44_100),
         channels: Some(2), // stereo
         samples: None,
     };
 
+    let audio_subsystem = sdl.audio().unwrap();
+
+    let mut freq = 0;
+
+    let mut producer: Option<Producer<StereoSample>> = None;
+
     let device = audio_subsystem
-        .open_queue::<i16, _>(None, &desired_spec)
+        .open_playback(None, &desired_spec, |spec| {
+            println!("Found audio device: {:?}", spec);
+            freq = spec.freq;
+
+            // Create a thread-safe SPSC fifo
+            let ringbuf_size = (spec.samples as usize) * 2;
+            let rb = RingBuffer::<StereoSample>::new(ringbuf_size);
+            let (prod, cons) = rb.split();
+
+            // move producer to the outer scope
+            producer = Some(prod);
+
+            GbaAudioCallback {
+                consumer: cons,
+                spec,
+            }
+        })
         .unwrap();
 
-    println!("Found audio device: {:?}", device.spec());
-
-    let freq = device.spec().freq;
     device.resume();
 
-    Sdl2AudioPlayer { device, freq }
+    Sdl2AudioPlayer {
+        _device: device,
+        freq,
+        producer: producer.unwrap(),
+    }
 }

src/plat/sdl2/main.rs

@@ -17,9 +17,9 @@ mod audio;
 mod input;
 mod video;
 
-use audio::{create_audio_player, Sdl2AudioPlayer};
+use audio::create_audio_player;
-use input::{create_input, Sdl2Input};
+use input::create_input;
-use video::{create_video_interface, Sdl2Video};
+use video::create_video_interface;
 
 extern crate rustboyadvance_ng;
 use rustboyadvance_ng::prelude::*;
@@ -85,7 +85,6 @@ fn main() {
                         keycode: Some(Keycode::Space),
                         ..
                     } => {
-                        audio.borrow_mut().device.clear(); // clear audio queue
                         frame_limiter = true;
                     }
                     Event::KeyDown {