test(audio): add APU register and channel tests
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dualfroz committed
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using System.Collections.Generic;
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using Xunit;
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using Xunit.Abstractions;
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namespace GameBoy.Tests
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{
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public sealed class ApuTests
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{
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private const int SampleRate = 44100;
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private const int CpuClock = 4194304;
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private readonly ITestOutputHelper output;
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public ApuTests(ITestOutputHelper output)
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{
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this.output = output;
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}
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private static Emulator NewMachine()
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{
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return new Emulator(TestRoms.BuildProgram());
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}
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private static void AdvanceSeconds(Emulator emulator, double seconds)
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{
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long ticks = (long)(seconds * CpuClock) / 4;
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for (long i = 0; i < ticks; i++)
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emulator.Tick4();
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}
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private static float[] DrainLeft(Emulator emulator)
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{
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int available = emulator.Apu.AvailableSamples;
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var interleaved = new float[available * 2];
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int frames = emulator.Apu.ReadSamples(interleaved);
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var left = new float[frames];
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for (int i = 0; i < frames; i++)
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left[i] = interleaved[i * 2];
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return left;
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}
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private static void ConfigureSquare1(Emulator emulator, int frequency, byte envelope)
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{
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emulator.WriteMemory(0xFF26, 0x80);
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emulator.WriteMemory(0xFF24, 0x77);
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emulator.WriteMemory(0xFF25, 0x11);
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emulator.WriteMemory(0xFF11, 0x80);
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emulator.WriteMemory(0xFF12, envelope);
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emulator.WriteMemory(0xFF13, (byte)(frequency & 0xFF));
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emulator.WriteMemory(0xFF14, (byte)(0x80 | ((frequency >> 8) & 0x07)));
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}
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[Fact]
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public void PoweredApuWithNoActiveChannelsIsSilent()
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{
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var emulator = NewMachine();
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emulator.WriteMemory(0xFF26, 0x80);
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emulator.WriteMemory(0xFF24, 0x77);
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emulator.WriteMemory(0xFF25, 0xFF);
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AdvanceSeconds(emulator, 0.2);
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float[] left = DrainLeft(emulator);
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Assert.True(left.Length > 8000, $"expected a full sample stream, got {left.Length}");
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foreach (float sample in left)
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Assert.Equal(0f, sample);
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}
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[Fact]
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public void SquareChannelAmplitudeMatchesMixerMath()
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{
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var emulator = NewMachine();
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ConfigureSquare1(emulator, 1024, 0xF0);
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AdvanceSeconds(emulator, 0.1);
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float[] left = DrainLeft(emulator);
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float min = float.MaxValue;
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float max = float.MinValue;
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foreach (float sample in left)
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{
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if (sample < min) min = sample;
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if (sample > max) max = sample;
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}
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output.WriteLine($"min={min} max={max}");
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Assert.InRange(max, 0.24f, 0.26f);
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Assert.InRange(min, -0.26f, -0.24f);
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}
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[Fact]
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public void SquareChannelPeriodMatchesProgrammedFrequency()
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{
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var emulator = NewMachine();
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int frequency = 1024;
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ConfigureSquare1(emulator, frequency, 0xF0);
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AdvanceSeconds(emulator, 0.5);
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float[] left = DrainLeft(emulator);
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double squareHz = 131072.0 / (2048 - frequency);
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double expectedSamplesPerPeriod = SampleRate / squareHz;
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double mean = 0;
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foreach (float sample in left)
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mean += sample;
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mean /= left.Length;
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var crossings = new List<int>();
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for (int i = 1; i < left.Length; i++)
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if (left[i - 1] <= mean && left[i] > mean)
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crossings.Add(i);
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Assert.True(crossings.Count > 20, $"too few periods detected: {crossings.Count}");
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double total = 0;
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for (int i = 1; i < crossings.Count; i++)
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total += crossings[i] - crossings[i - 1];
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double measured = total / (crossings.Count - 1);
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output.WriteLine($"expected {expectedSamplesPerPeriod:F2} samples/period, measured {measured:F2}");
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Assert.InRange(measured, expectedSamplesPerPeriod * 0.97, expectedSamplesPerPeriod * 1.03);
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}
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[Fact]
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public void DisablingDacSilencesARunningChannel()
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{
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var emulator = NewMachine();
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ConfigureSquare1(emulator, 1024, 0xF0);
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AdvanceSeconds(emulator, 0.05);
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float[] whilePlaying = DrainLeft(emulator);
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float loudest = 0;
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foreach (float sample in whilePlaying)
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if (System.MathF.Abs(sample) > loudest)
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loudest = System.MathF.Abs(sample);
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Assert.True(loudest > 0.1f, "channel should be audible before the DAC is disabled");
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emulator.WriteMemory(0xFF12, 0x00);
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emulator.Apu.ClearSamples();
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AdvanceSeconds(emulator, 0.05);
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float[] afterMute = DrainLeft(emulator);
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Assert.True(afterMute.Length > 1000);
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foreach (float sample in afterMute)
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Assert.Equal(0f, sample);
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}
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[Fact]
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public void NoiseChannelProducesTogglingOutput()
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{
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var emulator = NewMachine();
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emulator.WriteMemory(0xFF26, 0x80);
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emulator.WriteMemory(0xFF24, 0x77);
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emulator.WriteMemory(0xFF25, 0x88);
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emulator.WriteMemory(0xFF20, 0x00);
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emulator.WriteMemory(0xFF21, 0xF0);
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emulator.WriteMemory(0xFF22, 0x00);
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emulator.WriteMemory(0xFF23, 0x80);
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AdvanceSeconds(emulator, 0.1);
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float[] left = DrainLeft(emulator);
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float min = float.MaxValue;
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float max = float.MinValue;
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int transitions = 0;
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for (int i = 0; i < left.Length; i++)
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{
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if (left[i] < min) min = left[i];
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if (left[i] > max) max = left[i];
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if (i > 0 && left[i] != left[i - 1])
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transitions++;
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}
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output.WriteLine($"min={min} max={max} transitions={transitions}");
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Assert.True(max > 0.1f);
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Assert.True(min < -0.1f);
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Assert.True(transitions > 200, $"noise output barely changed: {transitions} transitions");
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}
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[Fact]
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public void WaveChannelPlaysProgrammedSamples()
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{
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var emulator = NewMachine();
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emulator.WriteMemory(0xFF26, 0x80);
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emulator.WriteMemory(0xFF24, 0x77);
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emulator.WriteMemory(0xFF25, 0x44);
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byte[] pattern = { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF, 0xFE, 0xDC, 0xBA, 0x98, 0x76, 0x54, 0x32, 0x10 };
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for (int i = 0; i < pattern.Length; i++)
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emulator.WriteMemory((ushort)(0xFF30 + i), pattern[i]);
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emulator.WriteMemory(0xFF1A, 0x80);
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emulator.WriteMemory(0xFF1B, 0x00);
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emulator.WriteMemory(0xFF1C, 0x20);
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emulator.WriteMemory(0xFF1D, 0x00);
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emulator.WriteMemory(0xFF1E, 0x84);
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AdvanceSeconds(emulator, 0.1);
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float[] left = DrainLeft(emulator);
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float min = float.MaxValue;
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float max = float.MinValue;
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foreach (float sample in left)
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{
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if (sample < min) min = sample;
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if (sample > max) max = sample;
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}
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output.WriteLine($"wave min={min} max={max}");
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Assert.True(max - min > 0.3f, "wave output should swing across the programmed ramp");
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}
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[Fact]
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public void LengthCounterDisablesChannelWhenEnabled()
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{
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var emulator = NewMachine();
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emulator.WriteMemory(0xFF26, 0x80);
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emulator.WriteMemory(0xFF11, (byte)(0x80 | 63));
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emulator.WriteMemory(0xFF12, 0xF0);
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emulator.WriteMemory(0xFF13, 0x00);
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emulator.WriteMemory(0xFF14, 0xC0);
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Assert.True((emulator.ReadMemory(0xFF26) & 0x01) != 0, "channel 1 should be active right after trigger");
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AdvanceSeconds(emulator, 0.02);
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Assert.True((emulator.ReadMemory(0xFF26) & 0x01) == 0, "channel 1 should have expired via the length counter");
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}
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[Fact]
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public void PowerOffClearsChannelStatus()
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{
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var emulator = NewMachine();
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ConfigureSquare1(emulator, 1024, 0xF0);
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Assert.True((emulator.ReadMemory(0xFF26) & 0x01) != 0);
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emulator.WriteMemory(0xFF26, 0x00);
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Assert.Equal(0x70, emulator.ReadMemory(0xFF26));
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emulator.Apu.ClearSamples();
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AdvanceSeconds(emulator, 0.02);
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float[] left = DrainLeft(emulator);
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foreach (float sample in left)
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Assert.Equal(0f, sample);
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}
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}
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}
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