WIP

Author: habedi

src/audio/output.zig

@@ -39,7 +39,7 @@ const NoiseState = struct {
     real_output_bit: u1 = 0,
     frequency_mode: u2 = 0,
     noise_type: NoiseType = .periodic,
-    shift_register: u16 = 0,
+    shift_register: u16 = 0x8000,
 };
 
 const LatchedCommand = struct {

src/audio/psg.zig

@@ -3,17 +3,30 @@ const testing = std.testing;
 const clock = @import("../clock.zig");
 
 pub const PendingAudioFrames = struct {
+    master_cycles: u32,
     fm_frames: u32,
     psg_frames: u32,
+    fm_start_remainder: u16,
+    psg_start_remainder: u16,
 };
 
 pub const AudioTiming = struct {
     fm_master_remainder: u16 = 0,
     psg_master_remainder: u16 = 0,
+    pending_master_cycles: u32 = 0,
     pending_fm_frames: u32 = 0,
     pending_psg_frames: u32 = 0,
+    pending_fm_start_remainder: u16 = 0,
+    pending_psg_start_remainder: u16 = 0,
 
     pub fn consumeMaster(self: *AudioTiming, master_cycles: u32) void {
+        if (self.pending_master_cycles == 0) {
+            self.pending_fm_start_remainder = self.fm_master_remainder;
+            self.pending_psg_start_remainder = self.psg_master_remainder;
+        }
+
+        self.pending_master_cycles += master_cycles;
+
         const fm_total = @as(u32, self.fm_master_remainder) + master_cycles;
         self.pending_fm_frames += fm_total / clock.fm_master_cycles_per_sample;
         self.fm_master_remainder = @intCast(fm_total % clock.fm_master_cycles_per_sample);
@@ -25,12 +38,18 @@ pub const AudioTiming = struct {
 
     pub fn takePending(self: *AudioTiming) PendingAudioFrames {
         const out = PendingAudioFrames{
+            .master_cycles = self.pending_master_cycles,
             .fm_frames = self.pending_fm_frames,
             .psg_frames = self.pending_psg_frames,
+            .fm_start_remainder = self.pending_fm_start_remainder,
+            .psg_start_remainder = self.pending_psg_start_remainder,
         };
 
+        self.pending_master_cycles = 0;
         self.pending_fm_frames = 0;
         self.pending_psg_frames = 0;
+        self.pending_fm_start_remainder = 0;
+        self.pending_psg_start_remainder = 0;
 
         return out;
     }
@@ -41,9 +60,29 @@ test "audio timing accrues FM/PSG native-rate frames from master cycles" {
     timing.consumeMaster(clock.ntsc_master_cycles_per_frame);
     const frames = timing.takePending();
 
+    try testing.expectEqual(clock.ntsc_master_cycles_per_frame, frames.master_cycles);
     try testing.expectEqual(@as(u32, 888), frames.fm_frames);
+    try testing.expectEqual(@as(u16, 0), frames.fm_start_remainder);
     try testing.expectEqual(@as(u16, 936), timing.fm_master_remainder);
 
     try testing.expectEqual(@as(u32, 3733), frames.psg_frames);
+    try testing.expectEqual(@as(u16, 0), frames.psg_start_remainder);
     try testing.expectEqual(@as(u16, 120), timing.psg_master_remainder);
 }
+
+test "audio timing snapshots start remainders for each pending window" {
+    var timing = AudioTiming{};
+
+    timing.consumeMaster(clock.fm_master_cycles_per_sample - 8);
+    const first = timing.takePending();
+    try testing.expectEqual(@as(u32, clock.fm_master_cycles_per_sample - 8), first.master_cycles);
+    try testing.expectEqual(@as(u32, 0), first.fm_frames);
+    try testing.expectEqual(@as(u16, 0), first.fm_start_remainder);
+    try testing.expectEqual(@as(u16, clock.fm_master_cycles_per_sample - 8), timing.fm_master_remainder);
+
+    timing.consumeMaster(16);
+    const second = timing.takePending();
+    try testing.expectEqual(@as(u32, 16), second.master_cycles);
+    try testing.expectEqual(@as(u32, 1), second.fm_frames);
+    try testing.expectEqual(@as(u16, clock.fm_master_cycles_per_sample - 8), second.fm_start_remainder);
+}