fix: resolve issue when handling event sooner than expected

src/apu.zig

@@ -200,7 +200,10 @@ 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;
         }
 
-        _ = SDL.SDL_AudioStreamPut(self.stream, &[2]u16{ final_left, final_right }, 2 * @sizeOf(u16));
+        // If we add 0x4040 to each sample the DC Offset is removed
+        // note: found this through guess and check
+        // FIXME: Pretty sure this is a dirty hack and should be fixed
+        _ = SDL.SDL_AudioStreamPut(self.stream, &[2]u16{ final_left + 0x4040, final_right + 0x4040 }, 2 * @sizeOf(u16));
         self.sched.push(.SampleAudio, self.sampleTicks() -| late);
     }
 

src/emu.zig

@@ -51,10 +51,7 @@ pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi) void {
     const frame_end = sched.tick + cycles_per_frame;
 
     while (true) {
-        const next = sched.nextTimestamp();
-        const run_until = std.math.min(next, frame_end);
-
-        while (sched.tick < run_until) {
+        while (sched.tick < std.math.min(frame_end, sched.nextTimestamp())) {
             if (cpu.bus.io.haltcnt == .Execute) cpu.step() else sched.tick += 1;
             cpu.handleDMATransfers();
         }

src/main.zig

@@ -239,10 +239,13 @@ fn initAudio(apu: *Apu) SDL.SDL_AudioDeviceID {
     return dev;
 }
 
-// FIXME: Sometimes, we hear garbage upon program start. Why?
 export fn audioCallback(userdata: ?*anyopaque, stream: [*c]u8, len: c_int) void {
     const apu = @ptrCast(*Apu, @alignCast(8, userdata));
-    _ = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
+    const written = SDL.SDL_AudioStreamGet(apu.stream, stream, len);
+
+    // If we don't write anything, play silence otherwise garbage will be played
+    // FIXME: I don't think this hack to remove DC Offset is acceptable :thinking:
+    if (written == 0) std.mem.set(u8, stream[0..@intCast(usize, len)], 0x80);
 }
 
 fn getSavePath(alloc: std.mem.Allocator) !?[]const u8 {

src/scheduler.zig

@@ -90,10 +90,12 @@ pub const Scheduler = struct {
         self.queue.add(.{ .kind = kind, .tick = self.now() + end }) catch unreachable;
     }
 
-    pub fn nextTimestamp(self: *Self) u64 {
-        if (self.queue.peek()) |e| return e.tick;
+    pub inline fn nextTimestamp(self: *const Self) u64 {
+        @setRuntimeSafety(false);
 
-        unreachable; // There's always the HeatDeath event scheduled
+        // Typically you'd use PriorityQueue.peek here, but there's always at least a HeatDeath
+        // event in the PQ so we can just do this instead. Should be faster in ReleaseSafe
+        return self.queue.items[0].tick;
     }
 };