From 668a5ca04101e5d0a3f3821de7dc8201ed8942b5 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 31 Dec 2024 10:25:11 -0500
Subject: [PATCH] Make a real attempt at some degree of audio.

---
 Machines/Commodore/Plus4/Audio.hpp | 35 ++++++++++++++++++++++--------
 Machines/Commodore/Plus4/Plus4.cpp |  4 ++++
 Machines/Commodore/Plus4/Video.hpp |  5 +++--
 3 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/Machines/Commodore/Plus4/Audio.hpp b/Machines/Commodore/Plus4/Audio.hpp
index 4bec24df9..471dd3851 100644
--- a/Machines/Commodore/Plus4/Audio.hpp
+++ b/Machines/Commodore/Plus4/Audio.hpp
@@ -13,8 +13,8 @@
 
 namespace Commodore::Plus4 {
 
-// PAL: / 160
-// NTSC: / 128
+// PAL: / 160	i.e. 5*32
+// NTSC: / 128 	i.e. 4*32
 
 // 111860.78125 = NTSC
 // 110840.46875 = PAL
@@ -26,23 +26,37 @@ public:
 
 	template <Outputs::Speaker::Action action>
 	void apply_samples(std::size_t size, Outputs::Speaker::MonoSample *const target) {
+		const auto count_frequency = [&](int index) {
+			if(!counts_[index]) {
+				counts_[index] = frequencies_[index] * frequency_multiplier_;
+				states_[index] ^= 1;
+			} else {
+				--counts_[index];
+			}
+		};
+
 		for(size_t c = 0; c < size; c++) {
+			count_frequency(0);
+			count_frequency(1);
 
 			Outputs::Speaker::apply<action>(
 				target[c],
 				Outputs::Speaker::MonoSample(
-					((r_ + c) & 128) ? external_volume_ : -external_volume_
+					(
+						((states_[0] & masks_[0]) * external_volume_) +
+						((states_[1] & masks_[1]) * external_volume_)
+					) * volume_
 				));
 		}
 		r_ += size;
 	}
 
 	void set_sample_volume_range(const std::int16_t range) {
-		external_volume_ = range;
+		external_volume_ = range >> 5;
 	}
 
 	bool is_zero_level() const {
-		return !(sound1_on_ || sound2_on_ || sound2_noise_on_) || !volume_;
+		return !(masks_[0] || masks_[1] || sound2_noise_on_) || !volume_;
 	}
 
 	template <int channel> void set_frequency_low(uint8_t value) {
@@ -60,8 +74,8 @@ public:
 	void set_constrol(uint8_t value) {
 		audio_queue_.enqueue([this, value] {
 			volume_ = value & 0xf;
-			sound1_on_ = value & 0x10;
-			sound2_on_ = value & 0x20;
+			masks_[0] = (value & 0x10) ? 1 : 0;
+			masks_[1] = (value & 0x20) ? 1 : 0;
 			sound2_noise_on_ = value & 0x40;
 			sound_dc_ = value & 0x80;
 		});
@@ -74,9 +88,12 @@ private:
 	// Audio-thread state.
 	int16_t external_volume_ = 0;
 	int frequencies_[2]{};
+	int frequency_multiplier_ = 5;
+	int counts_[2]{};
+
+	int states_[2]{};
+	int masks_[2]{};
 
-	bool sound1_on_ = false;
-	bool sound2_on_ = false;
 	bool sound2_noise_on_ = false;
 	bool sound_dc_ = false;
 	uint8_t volume_ = 0;
diff --git a/Machines/Commodore/Plus4/Plus4.cpp b/Machines/Commodore/Plus4/Plus4.cpp
index 9b12523da..f8ec1fd9c 100644
--- a/Machines/Commodore/Plus4/Plus4.cpp
+++ b/Machines/Commodore/Plus4/Plus4.cpp
@@ -444,6 +444,10 @@ private:
 
 	void run_for(const Cycles cycles) final {
 		m6502_.run_for(cycles);
+
+		// I don't know why.
+		update_audio();
+		audio_queue_.perform();
 	}
 
 	void flush_output(int outputs) override {
diff --git a/Machines/Commodore/Plus4/Video.hpp b/Machines/Commodore/Plus4/Video.hpp
index 795764d4a..09e233794 100644
--- a/Machines/Commodore/Plus4/Video.hpp
+++ b/Machines/Commodore/Plus4/Video.hpp
@@ -307,7 +307,6 @@ public:
 					);
 
 					shifter_.advance();
-
 					++video_counter_;
 				}
 				if(increment_character_position_ && character_fetch_) {
@@ -477,7 +476,9 @@ public:
 				break;
 
 				case HorizontalEvent::BeginShiftRegister:
-					character_window_ = video_shift_ = enable_display_;
+					if(enable_display_) {
+						character_window_ = video_shift_ = true;
+					}
 					next_pixels_ = 0;
 				break;
 			}