From 3b7d5edcda98b5a4217dc7fbede3eb326118c8c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Wed, 1 Mar 2023 12:01:46 +0000
Subject: [PATCH] =?UTF-8?q?feat:=20initial=20length=20and=20sweep=20audio?=
=?UTF-8?q?=20support=20The=20emulator=20is=20now=20sounding=20more=20like?=
=?UTF-8?q?=20a=20real=20audio=20player=20=F0=9F=8E=A7.?=
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---
frontends/sdl/src/main.rs | 6 +-
src/apu.rs | 130 +++++++++++++++++++++++++++++++++-----
2 files changed, 120 insertions(+), 16 deletions(-)
diff --git a/frontends/sdl/src/main.rs b/frontends/sdl/src/main.rs
index 8cd7607d..4dcb15e3 100644
--- a/frontends/sdl/src/main.rs
+++ b/frontends/sdl/src/main.rs
@@ -22,6 +22,10 @@ const SCREEN_SCALE: f32 = 2.0;
/// The base title to be used in the window.
static TITLE: &str = "Boytacean";
+/// Base audio volume to be used as the basis of the
+/// amplification level of the volume
+static VOLUME: f32 = 100.0;
+
pub struct Benchmark {
count: usize,
}
@@ -312,7 +316,7 @@ impl Emulator {
.system
.audio_buffer()
.iter()
- .map(|v| *v as f32 / 14.0)
+ .map(|v| *v as f32 / VOLUME)
.collect::<Vec<f32>>();
audio.device.queue_audio(&audio_buffer).unwrap();
}
diff --git a/src/apu.rs b/src/apu.rs
index 588c1e4e..3c934c3d 100644
--- a/src/apu.rs
+++ b/src/apu.rs
@@ -7,9 +7,17 @@ const DUTY_TABLE: [[u8; 8]; 4] = [
[0, 1, 1, 1, 1, 1, 1, 0],
];
+pub enum Channel {
+ Ch1,
+ Ch2,
+ Ch3,
+ Ch4,
+}
+
pub struct Apu {
ch1_timer: u16,
ch1_sequence: u8,
+ ch1_sweep_sequence: u8,
ch1_output: u8,
ch1_sweep_slope: u8,
ch1_sweep_increase: bool,
@@ -48,6 +56,9 @@ pub struct Apu {
wave_ram: [u8; 16],
+ sampling_frequency: u16,
+ sequencer: u16,
+ sequencer_step: u8,
output_timer: u16,
audio_buffer: Vec<u8>,
}
@@ -57,6 +68,7 @@ impl Apu {
Self {
ch1_timer: 0,
ch1_sequence: 0,
+ ch1_sweep_sequence: 0,
ch1_output: 0,
ch1_sweep_slope: 0x0,
ch1_sweep_increase: false,
@@ -95,6 +107,12 @@ impl Apu {
wave_ram: [0u8; 16],
+ sampling_frequency: 44100,
+
+ /// Internal sequencer counter that runs at 512Hz
+ /// used for the activation of the tick actions.
+ sequencer: 0,
+ sequencer_step: 0,
output_timer: 0,
audio_buffer: Vec::new(),
}
@@ -103,7 +121,7 @@ impl Apu {
pub fn clock(&mut self, cycles: u8) {
// @TODO the performance here requires improvement
for _ in 0..cycles {
- self.cycle();
+ self.tick();
}
}
@@ -118,8 +136,8 @@ impl Apu {
match addr {
// 0xFF10 — NR10: Channel 1 sweep
0xff10 => {
- self.ch1_sweep_slope = value & 0x03;
- self.ch1_sweep_increase = value & 0x04 == 0x04;
+ self.ch1_sweep_slope = value & 0x07;
+ self.ch1_sweep_increase = value & 0x08 == 0x00;
self.ch1_sweep_pace = (value & 0x70) >> 4;
}
// 0xFF11 — NR11: Channel 1 length timer & duty cycle
@@ -206,8 +224,57 @@ impl Apu {
}
}
+ pub fn output(&self) -> u8 {
+ self.ch1_output + self.ch2_output
+ }
+
+ pub fn audio_buffer(&self) -> &Vec<u8> {
+ &self.audio_buffer
+ }
+
+ pub fn audio_buffer_mut(&mut self) -> &mut Vec<u8> {
+ &mut self.audio_buffer
+ }
+
+ pub fn clear_audio_buffer(&mut self) {
+ self.audio_buffer.clear();
+ }
+
#[inline(always)]
- pub fn cycle(&mut self) {
+ fn tick(&mut self) {
+ self.sequencer += 1;
+ if self.sequencer >= 8192 {
+ // each of these steps runs at 518/8 Hz = 64Hz
+ match self.sequencer_step {
+ 0 => {
+ self.tick_length_all();
+ }
+ 1 => (),
+ 2 => {
+ self.tick_ch1_sweep();
+ self.tick_length_all();
+ }
+ 3 => (),
+ 4 => {
+ self.tick_length_all();
+ }
+ 5 => (),
+ 6 => {
+ self.tick_ch1_sweep();
+ self.tick_length_all();
+ }
+ 7 => {
+ //channels[0]->envelope_clock();
+ //channels[1]->envelope_clock();
+ //channels[3]->envelope_clock();
+ }
+ _ => (),
+ }
+
+ self.sequencer = 0;
+ self.sequencer_step = (self.sequencer_step + 1) & 7;
+ }
+
self.ch1_timer = self.ch1_timer.saturating_sub(1);
if self.ch1_timer == 0 {
self.ch1_timer = (2048 - self.ch1_wave_length) << 2;
@@ -246,24 +313,57 @@ impl Apu {
if self.output_timer == 0 {
self.audio_buffer.push(self.output());
// @TODO target sampling rate is hardcoded, need to softcode this
- self.output_timer = (4194304.0 / 44100.0) as u16;
+ self.output_timer = (4194304.0 / self.sampling_frequency as f32) as u16;
}
}
- pub fn output(&self) -> u8 {
- self.ch1_output + self.ch2_output
- }
-
- pub fn audio_buffer(&self) -> &Vec<u8> {
- &self.audio_buffer
+ fn tick_length_all(&mut self) {
+ self.tick_length(Channel::Ch1);
+ self.tick_length(Channel::Ch2);
+ self.tick_length(Channel::Ch3);
+ self.tick_length(Channel::Ch4);
}
- pub fn audio_buffer_mut(&mut self) -> &mut Vec<u8> {
- &mut self.audio_buffer
+ fn tick_length(&mut self, channel: Channel) {
+ match channel {
+ Channel::Ch1 => {
+ self.ch1_length_timer = self.ch1_length_timer.saturating_add(1);
+ if self.ch1_length_timer >= 64 {
+ self.ch1_enabled = false;
+ self.ch1_length_timer = 0;
+ }
+ }
+ Channel::Ch2 => {
+ self.ch2_length_timer = self.ch2_length_timer.saturating_add(1);
+ if self.ch2_length_timer >= 64 {
+ self.ch2_enabled = false;
+ self.ch2_length_timer = 0;
+ }
+ }
+ Channel::Ch3 => (),
+ Channel::Ch4 => (),
+ }
}
- pub fn clear_audio_buffer(&mut self) {
- self.audio_buffer.clear();
+ fn tick_ch1_sweep(&mut self) {
+ if self.ch1_sweep_pace == 0x0 {
+ return;
+ }
+ self.ch1_sweep_sequence += 1;
+ if self.ch1_sweep_sequence >= self.ch1_sweep_pace {
+ let divisor = (1 as u16) << self.ch1_sweep_slope as u16;
+ let delta = (self.ch1_wave_length as f32 / divisor as f32) as u16;
+ if self.ch1_sweep_increase {
+ self.ch1_wave_length = self.ch1_wave_length.saturating_add(delta);
+ } else {
+ self.ch1_wave_length = self.ch1_wave_length.saturating_sub(delta);
+ }
+ if self.ch1_wave_length > 0x07ff {
+ self.ch1_enabled = false;
+ self.ch1_wave_length = 0x07ff;
+ }
+ self.ch1_sweep_sequence = 0;
+ }
}
}
--
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