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feat: schedule audio sampling on scheduler 

DMA sound in games like Pokemon Emerald, Chobits, Love Hina, and Kirby:
Nightmare in Dream Land sound great save for conerns about resampling
This commit is contained in:
Rekai Nyangadzayi Musuka 2022-04-14 05:58:32 -03:00
parent 92cabd248b
commit 172a59aefb
6 changed files with 67 additions and 69 deletions
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2
src/Bus.zig
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@ -41,7 +41,7 @@ pub fn init(alloc: Allocator, sched: *Scheduler, paths: FilePaths) !Self {
.pak = try GamePak.init(alloc, paths.rom, paths.save),
.bios = try Bios.init(alloc, paths.bios),
.ppu = try Ppu.init(alloc, sched),
.apu = Apu.init(),
.apu = Apu.init(sched),
.iwram = try Iwram.init(alloc),
.ewram = try Ewram.init(alloc),
.dma = DmaControllers.init(),

98
src/apu.zig
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@ -1,7 +1,9 @@
const std = @import("std");
const SDL = @import("sdl2");
const io = @import("bus/io.zig");
const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
const Scheduler = @import("scheduler.zig").Scheduler;
const SoundFifo = std.fifo.LinearFifo(u8, .{ .Static = 0x20 });
const AudioDeviceId = SDL.SDL_AudioDeviceID;
@ -9,6 +11,9 @@ const AudioDeviceId = SDL.SDL_AudioDeviceID;
const intToBytes = @import("util.zig").intToBytes;
const log = std.log.scoped(.APU);
const sample_rate = 32768;
const sample_ticks = 280896 * 60 / sample_rate;
pub const Apu = struct {
const Self = @This();
@ -25,9 +30,10 @@ pub const Apu = struct {
cnt: io.SoundControl,
dev: ?AudioDeviceId,
sched: *Scheduler,
pub fn init() Self {
return .{
pub fn init(sched: *Scheduler) Self {
const apu: Self = .{
.ch1 = ToneSweep.init(),
.ch2 = Tone.init(),
.ch3 = Wave.init(),
@ -41,7 +47,11 @@ pub const Apu = struct {
.bias = .{ .raw = 0x0200 },
.dev = null,
.sched = sched,
};
sched.push(.SampleAudio, sched.now() + sample_ticks);
return apu;
}
pub fn attachAudioDevice(self: *Self, dev: AudioDeviceId) void {
@ -53,8 +63,8 @@ pub const Apu = struct {
// Reinitializing instead of resetting is fine because
// the FIFOs I'm using are stack allocated and 0x20 bytes big
if (new.sa_reset.read()) self.chA.fifo = SoundFifo.init();
if (new.sb_reset.read()) self.chB.fifo = SoundFifo.init();
if (new.chA_reset.read()) self.chA.fifo = SoundFifo.init();
if (new.chB_reset.read()) self.chB.fifo = SoundFifo.init();
self.dma_cnt = new;
}
@ -75,19 +85,35 @@ pub const Apu = struct {
self.bias.raw = (@as(u16, byte) << 8) | (self.bias.raw & 0xFF);
}
pub fn handleTimerOverflow(self: *Self, kind: DmaSoundKind, cpu: *Arm7tdmi) void {
pub fn sampleAudio(self: *Self, late: u64) void {
const chA = if (self.dma_cnt.chA_vol.read()) self.chA.amplitude() else self.chA.amplitude() / 2;
const chA_left = if (self.dma_cnt.chA_left.read()) chA else 0;
const chA_right = if (self.dma_cnt.chA_right.read()) chA else 0;
const chB = if (self.dma_cnt.chB_vol.read()) self.chB.amplitude() else self.chB.amplitude() / 2;
const chB_left = if (self.dma_cnt.chB_left.read()) chB else 0;
const chB_right = if (self.dma_cnt.chB_right.read()) chB else 0;
const left = (chA_left + chB_left) / 2;
const right = (chA_right + chB_right) / 2;
if (self.dev) |dev| _ = SDL.SDL_QueueAudio(dev, &[2]f32{ left, right }, 2 * @sizeOf(f32));
self.sched.push(.SampleAudio, self.sched.now() + sample_ticks - late);
}
pub fn handleTimerOverflow(self: *Self, cpu: *Arm7tdmi, tim_id: u3) void {
if (!self.cnt.apu_enable.read()) return;
const samples = switch (kind) {
.A => blk: {
break :blk self.chA.handleTimerOverflow(cpu, self.dma_cnt);
},
.B => blk: {
break :blk self.chB.handleTimerOverflow(cpu, self.dma_cnt);
},
};
if (@boolToInt(self.dma_cnt.chA_timer.read()) == tim_id) {
self.chA.updateSample();
if (self.chA.len() <= 15) cpu.bus.dma._1.enableSoundDma(0x0400_00A0);
}
if (self.dev) |dev| _ = SDL.SDL_QueueAudio(dev, &samples, 2);
if (@boolToInt(self.dma_cnt.chB_timer.read()) == tim_id) {
self.chB.updateSample();
if (self.chB.len() <= 15) cpu.bus.dma._2.enableSoundDma(0x0400_00A4);
}
}
};
@ -207,55 +233,31 @@ pub fn DmaSound(comptime kind: DmaSoundKind) type {
const Self = @This();
fifo: SoundFifo,
kind: DmaSoundKind,
sample: i8,
fn init() Self {
return .{ .fifo = SoundFifo.init(), .kind = kind };
return .{
.fifo = SoundFifo.init(),
.kind = kind,
.sample = 0,
};
}
pub fn push(self: *Self, value: u32) void {
self.fifo.write(&intToBytes(u32, value)) catch {};
}
pub fn pop(self: *Self) u8 {
return self.fifo.readItem() orelse 0;
}
pub fn len(self: *const Self) usize {
return self.fifo.readableLength();
}
pub fn handleTimerOverflow(self: *Self, cpu: *Arm7tdmi, cnt: io.DmaSoundControl) [2]u8 {
const sample = self.pop();
var left: u8 = 0;
var right: u8 = 0;
var fifo_addr: u32 = undefined;
switch (kind) {
.A => {
const vol = @boolToInt(!cnt.sa_vol.read()); // if unset, vol is 50%
if (cnt.sa_left_enable.read()) left = sample >> vol;
if (cnt.sa_right_enable.read()) right = sample >> vol;
fifo_addr = 0x0400_00A0;
},
.B => {
const vol = @boolToInt(!cnt.sb_vol.read()); // if unset, vol is 50%
if (cnt.sb_left_enable.read()) left = sample >> vol;
if (cnt.sb_right_enable.read()) right = sample >> vol;
fifo_addr = 0x0400_00A4;
},
pub fn updateSample(self: *Self) void {
if (self.fifo.readItem()) |sample| self.sample = @bitCast(i8, sample);
}
if (self.len() <= 15) {
cpu.bus.dma._1.enableSoundDma(fifo_addr);
cpu.bus.dma._2.enableSoundDma(fifo_addr);
}
return .{ left, right };
pub fn amplitude(self: *const Self) f32 {
return @intToFloat(f32, self.sample) / 127.5 - (1 / 255);
}
};
}

20
src/bus/io.zig
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@ -595,20 +595,20 @@ pub const ChannelVolumeControl = extern union {
/// Read / Write
pub const DmaSoundControl = extern union {
ch_vol: Bitfield(u16, 0, 2),
sa_vol: Bit(u16, 2),
sb_vol: Bit(u16, 3),
chA_vol: Bit(u16, 2),
chB_vol: Bit(u16, 3),
sa_right_enable: Bit(u16, 8),
sa_left_enable: Bit(u16, 9),
sa_timer: Bit(u16, 10),
chA_right: Bit(u16, 8),
chA_left: Bit(u16, 9),
chA_timer: Bit(u16, 10),
/// Write only?
sa_reset: Bit(u16, 11),
chA_reset: Bit(u16, 11),
sb_right_enable: Bit(u16, 12),
sb_left_enable: Bit(u16, 13),
sb_timer: Bit(u16, 14),
chB_right: Bit(u16, 12),
chB_left: Bit(u16, 13),
chB_timer: Bit(u16, 14),
/// Write only?
sb_reset: Bit(u16, 15),
chB_reset: Bit(u16, 15),
raw: u16,
};

8
src/bus/timer.zig
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@ -109,13 +109,7 @@ fn Timer(comptime id: u2) type {
// DMA Sound Things
if (id == 0 or id == 1) {
const apu = &cpu.bus.apu;
const a_tim = @boolToInt(apu.dma_cnt.sa_timer.read());
const b_tim = @boolToInt(apu.dma_cnt.sb_timer.read());
if (a_tim == id) apu.handleTimerOverflow(.A, cpu);
if (b_tim == id) apu.handleTimerOverflow(.B, cpu);
cpu.bus.apu.handleTimerOverflow(cpu, id);
}
// Perform Cascade Behaviour

4
src/main.zig
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@ -242,9 +242,9 @@ fn initAudio() SDL.SDL_AudioDeviceID {
var have: SDL.SDL_AudioSpec = undefined;
var want = std.mem.zeroes(SDL.SDL_AudioSpec);
want.freq = 32768;
want.format = SDL.AUDIO_S8;
want.format = SDL.AUDIO_F32;
want.channels = 2;
want.samples = 0x200;
want.samples = 0x100;
want.callback = null;
const dev = SDL.SDL_OpenAudioDevice(null, 0, &want, &have, 0);

2
src/scheduler.zig
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@ -51,6 +51,7 @@ pub const Scheduler = struct {
3 => cpu.bus.tim._3.handleOverflow(cpu, late),
}
},
.SampleAudio => cpu.bus.apu.sampleAudio(late),
.HBlank => cpu.bus.ppu.handleHBlankEnd(cpu, late), // The end of a HBlank
.VBlank => cpu.bus.ppu.handleHDrawEnd(cpu, late), // The end of a VBlank
}
@ -102,4 +103,5 @@ pub const EventKind = union(enum) {
VBlank,
Draw,
TimerOverflow: u2,
SampleAudio,
};