From 99fa86a67ecd4358790c838742a8fa93522ca3ef Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 20 Apr 2020 18:40:47 -0400
Subject: [PATCH] Adds a test for lookup sine. And fixes lookup sine.

---
 Components/OPL2/Implementation/Tables.hpp    |  2 +-
 OSBindings/Mac/Clock SignalTests/OPLTests.mm | 60 ++++++++++++++++++--
 2 files changed, 56 insertions(+), 6 deletions(-)

diff --git a/Components/OPL2/Implementation/Tables.hpp b/Components/OPL2/Implementation/Tables.hpp
index 66fcf71fd..c7839785d 100644
--- a/Components/OPL2/Implementation/Tables.hpp
+++ b/Components/OPL2/Implementation/Tables.hpp
@@ -82,7 +82,7 @@ constexpr LogSign negative_log_sin(int x) {
 	constexpr int16_t mask[] = { 0, 255 };
 
 	return {
-		.log = log_sin[x & 255] ^ mask[(x >> 8) & 1],
+		.log = log_sin[(x & 255) ^ mask[(x >> 8) & 1]],
 		.sign = sign[(x >> 9) & 1]
 	};
 }
diff --git a/OSBindings/Mac/Clock SignalTests/OPLTests.mm b/OSBindings/Mac/Clock SignalTests/OPLTests.mm
index 1c39fe0b4..e4e8faeff 100644
--- a/OSBindings/Mac/Clock SignalTests/OPLTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/OPLTests.mm	
@@ -9,6 +9,7 @@
 #import <XCTest/XCTest.h>
 
 #include "OPL2.hpp"
+#include <cmath>
 
 @interface OPLTests: XCTestCase
 @end
@@ -16,6 +17,18 @@
 @implementation OPLTests {
 }
 
+- (void)testSineLookup {
+	for(int c = 0; c < 1024; ++c) {
+		const auto logSin = Yamaha::OPL::negative_log_sin(c);
+		const auto level = Yamaha::OPL::power_two(logSin);
+
+		double fl_angle = double(c) * M_PI / 512.0;
+		double fl_level = sin(fl_angle);
+
+		XCTAssertLessThanOrEqual(fabs(fl_level - double(level) / 4096.0), 0.01, "Sine varies by more than 0.01 at angle %d", c);
+	}
+}
+
 - (void)testADSR {
 	Yamaha::OPL::Operator test_operator;
 	Yamaha::OPL::OperatorState test_state;
@@ -23,18 +36,55 @@
 	test_operator.set_attack_decay(0x88);
 	test_operator.set_sustain_release(0x88);
 
-	// While key is off, ADSR attenuation should remain above 511.
+	// While key is off, output level should remain at 0.
 	for(int c = 0; c < 1024; ++c) {
-		test_operator.update(test_state, false, 0, 0);
-		XCTAssertGreaterThanOrEqual(test_state.attenuation, 511);
+		test_operator.update(test_state, false, 0, 0, 0);
+		XCTAssertGreaterThanOrEqual(test_state.level(), 0);
 	}
 
 	// Set key on...
 	for(int c = 0; c < 4096; ++c) {
-		test_operator.update(test_state, true, 0, 0);
-		NSLog(@"%d", test_state.attenuation);
+		test_operator.update(test_state, true, 0, 0, 0);
+		NSLog(@"%d", test_state.level());
 	}
+}
 
+- (void)testFM {
+	Yamaha::OPL::Operator modulator, carrier;
+	Yamaha::OPL::Channel channel;
+
+	// Set: AM = 0, PM = 0, EG = 1, KR = 0, MUL = 0
+	modulator.set_am_vibrato_hold_sustain_ksr_multiple(0x20);
+	carrier.set_am_vibrato_hold_sustain_ksr_multiple(0x20);
+
+	// Set: KL = 0, TL = 0
+	modulator.set_scaling_output(0x3f);
+	carrier.set_scaling_output(0);
+
+	// Set: waveform = 0.
+	modulator.set_waveform(0);
+	carrier.set_waveform(0);
+
+	// Set FB = 0, use FM synthesis.
+	channel.set_feedback_mode(1);
+
+	// Set: AR = 15, DR = 0.
+	modulator.set_attack_decay(0xf0);
+	carrier.set_attack_decay(0xf0);
+
+	// Set: SL = 0, RR = 15.
+	modulator.set_sustain_release(0x0f);
+	carrier.set_sustain_release(0x0f);
+
+	// Set 16384 samples for 1 period, and key-on.
+	channel.set_frequency_low(0x40);
+	channel.set_9bit_frequency_octave_key_on(0x10);
+
+	// Grab a bunch of samples.
+	for(int c = 0; c < 16384; ++c) {
+		printf("%d\n", channel.update(&modulator, &carrier));
+	}
+	printf("\n");
 }
 
 @end