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chore: emu audio sync code to emu.zig

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-05-23 12:05:57 -03:00
parent e70fe73899
commit 24a8905c29
2 changed files with 53 additions and 28 deletions
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2
src/apu.zig
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@ -200,8 +200,6 @@ pub const Apu = struct {
self.stream = SDL.SDL_NewAudioStream(SDL.AUDIO_U16, 2, @intCast(c_int, self.sampleRate()), SDL.AUDIO_U16, 2, host_sample_rate) orelse unreachable;
}
while (SDL.SDL_AudioStreamAvailable(self.stream) > (@sizeOf(i16) * 2 * 0x800)) {}
_ = SDL.SDL_AudioStreamPut(self.stream, &[2]u16{ final_left, final_right }, 2 * @sizeOf(u16));
self.sched.push(.SampleAudio, self.sampleTicks() -| late);
}

79
src/emu.zig
View File

@ -1,4 +1,5 @@
const std = @import("std");
const SDL = @import("sdl2");
const Bus = @import("Bus.zig");
const Scheduler = @import("scheduler.zig").Scheduler;
@ -9,6 +10,8 @@ const Timer = std.time.Timer;
const Thread = std.Thread;
const Atomic = std.atomic.Atomic;
const audio_sync = true;
// 228 Lines which consist of 308 dots (which are 4 cycles long)
const cycles_per_frame: u64 = 228 * (308 * 4); //280896
const clock_rate: u64 = 1 << 24; // 16.78MHz
@ -33,6 +36,8 @@ const RunKind = enum {
};
pub fn run(kind: RunKind, quit: *Atomic(bool), fps: *EmulatorFps, sched: *Scheduler, cpu: *Arm7tdmi) void {
if (audio_sync) log.info("Audio sync enabled", .{});
switch (kind) {
.Unlimited => runUnsynchronized(quit, sched, cpu, null),
.Limited => runSynchronized(quit, sched, cpu, null),
@ -56,50 +61,78 @@ pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi) void {
}
}
fn syncToAudio(cpu: *const Arm7tdmi) void {
const stream = cpu.bus.apu.stream;
const min_sample_count = 0x800;
// Busy Loop while we wait for the Audio system to catch up
while (SDL.SDL_AudioStreamAvailable(stream) > (@sizeOf(u16) * 2) * min_sample_count) {}
}
pub fn runUnsynchronized(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, fps: ?*EmulatorFps) void {
log.info("Emulation thread w/out video sync", .{});
if (fps) |tracker| {
log.info("Start unsynchronized emu thread w/ fps tracking", .{});
log.info("FPS Tracking Enabled", .{});
while (!quit.load(.SeqCst)) {
runFrame(sched, cpu);
if (audio_sync) syncToAudio(cpu);
tracker.completeFrame();
}
} else {
log.info("Start unsynchronized emu thread", .{});
while (!quit.load(.SeqCst)) runFrame(sched, cpu);
while (!quit.load(.SeqCst)) {
runFrame(sched, cpu);
if (audio_sync) syncToAudio(cpu);
}
}
}
pub fn runSynchronized(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi, fps: ?*EmulatorFps) void {
log.info("Emulation thread w/ video sync", .{});
var timer = Timer.start() catch unreachable;
var wake_time: u64 = frame_period;
if (fps) |tracker| {
log.info("Start synchronized emu thread w/ fps tracking", .{});
log.info("FPS Tracking Enabled", .{});
while (!quit.load(.SeqCst)) {
runSyncCore(sched, cpu, &timer, &wake_time);
runFrame(sched, cpu);
const new_wake_time = syncToVideo(&timer, wake_time);
// Spin to make up the difference of OS scheduler innacuracies
// If we happen to also be syncing to audio, we choose to spin on
// the amount of time needed for audio to catch up rather than
// our expected wake-up time
if (audio_sync) syncToAudio(cpu) else spinLoop(&timer, wake_time);
wake_time = new_wake_time;
tracker.completeFrame();
}
} else {
log.info("Start synchronized emu thread", .{});
while (!quit.load(.SeqCst)) runSyncCore(sched, cpu, &timer, &wake_time);
while (!quit.load(.SeqCst)) {
runFrame(sched, cpu);
const new_wake_time = syncToVideo(&timer, wake_time);
// see above comment
if (audio_sync) syncToAudio(cpu) else spinLoop(&timer, wake_time);
wake_time = new_wake_time;
}
}
}
inline fn runSyncCore(sched: *Scheduler, cpu: *Arm7tdmi, timer: *Timer, wake_time: *u64) void {
runFrame(sched, cpu);
inline fn syncToVideo(timer: *Timer, wake_time: u64) u64 {
// Use the OS scheduler to put the emulation thread to sleep
const maybe_recalc_wake_time = sleep(timer, wake_time);
// Put the Thread to Sleep + Backup Spin Loop
// This saves on resource usage when frame limiting
sleep(timer, wake_time);
// Update to the new wake time
wake_time.* += frame_period;
// If sleep() determined we need to adjust our wake up time, do so
// otherwise predict our next wake up time according to the frame period
return if (maybe_recalc_wake_time) |recalc| recalc else wake_time + frame_period;
}
pub fn runBusyLoop(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi) void {
log.info("Start synchronized emu thread using busy loop", .{});
log.info("Emulation thread with video sync using busy loop", .{});
var timer = Timer.start() catch unreachable;
var wake_time: u64 = frame_period;
@ -112,21 +145,17 @@ pub fn runBusyLoop(quit: *Atomic(bool), sched: *Scheduler, cpu: *Arm7tdmi) void
}
}
fn sleep(timer: *Timer, wake_time: *u64) void {
fn sleep(timer: *Timer, wake_time: u64) ?u64 {
// const step = std.time.ns_per_ms * 10; // 10ms
const timestamp = timer.read();
// ns_late is non zero if we are late.
const ns_late = timestamp -| wake_time.*;
const ns_late = timestamp -| wake_time;
// If we're more than a frame late, skip the rest of this loop
// Recalculate what our new wake time should be so that we can
// get "back on track"
if (ns_late > frame_period) {
wake_time.* = timestamp + frame_period;
return;
}
if (ns_late > frame_period) return timestamp + frame_period;
const sleep_for = frame_period - ns_late;
// // Employ several sleep calls in periods of 10ms
@ -139,9 +168,7 @@ fn sleep(timer: *Timer, wake_time: *u64) void {
std.time.sleep(sleep_for);
// Spin to make up the difference if there is a need
// Make sure that we're using the old wake time and not the onne we recalculated
spinLoop(timer, wake_time.*);
return null;
}
fn spinLoop(timer: *Timer, wake_time: u64) void {