XCEngine/tests/Components/test_audio_mixer.cpp

#include <gtest/gtest.h>

#include <XCEngine/Audio/AudioMixer.h>
#include <XCEngine/Audio/Equalizer.h>
#include <XCEngine/Audio/FFTFilter.h>
#include <XCEngine/Audio/IAudioEffect.h>
#include <XCEngine/Audio/Reverbation.h>
#include <algorithm>
#include <cmath>
#include <vector>

using namespace XCEngine::Audio;

namespace {

class OffsetEffect final : public IAudioEffect {
public:
    explicit OffsetEffect(float offset) : m_offset(offset) {}

    void ProcessAudio(float* buffer, uint32 frameCount, uint32 channels) override {
        ++callCount;
        const size_t totalSamples = static_cast<size_t>(frameCount) * channels;
        for (size_t i = 0; i < totalSamples; ++i) {
            buffer[i] += m_offset;
        }
    }

    int callCount = 0;

private:
    float m_offset = 0.0f;
};

TEST(AudioMixer, AppliesMasterAndChannelVolume) {
    AudioMixer mixer;
    mixer.SetVolume(0.5f);
    mixer.SetChannelVolume(AudioChannel::FrontLeft, 0.25f);
    mixer.SetChannelVolume(AudioChannel::FrontRight, 1.0f);

    float buffer[] = {1.0f, 1.0f, 1.0f, 1.0f};
    mixer.ProcessAudio(buffer, 2, 2);

    EXPECT_FLOAT_EQ(buffer[0], 0.125f);
    EXPECT_FLOAT_EQ(buffer[1], 0.5f);
    EXPECT_FLOAT_EQ(buffer[2], 0.125f);
    EXPECT_FLOAT_EQ(buffer[3], 0.5f);
}

TEST(AudioMixer, MuteSilencesBuffer) {
    AudioMixer mixer;
    mixer.SetMute(true);

    float buffer[] = {0.5f, -0.5f};
    mixer.ProcessAudio(buffer, 1, 2);

    EXPECT_FLOAT_EQ(buffer[0], 0.0f);
    EXPECT_FLOAT_EQ(buffer[1], 0.0f);
}

TEST(AudioMixer, EffectsRunAfterGain) {
    AudioMixer mixer;
    mixer.SetVolume(0.5f);
    OffsetEffect effect(0.25f);
    mixer.AddEffect(&effect);

    float buffer[] = {1.0f, -1.0f};
    mixer.ProcessAudio(buffer, 1, 2);

    EXPECT_EQ(effect.callCount, 1);
    EXPECT_FLOAT_EQ(buffer[0], 0.75f);
    EXPECT_FLOAT_EQ(buffer[1], -0.25f);
}

TEST(AudioMixer, EqualizerWetMixControlsProcessedSignal) {
    AudioMixer mixer;
    Equalizer equalizer;
    equalizer.SetBandCount(1);
    equalizer.SetBandFrequency(0, 2000.0f);
    equalizer.SetBandGain(0, 12.0f);
    equalizer.SetBandQ(0, 0.7f);
    mixer.AddEffect(&equalizer);

    std::vector<float> dryBuffer(64, 0.0f);
    dryBuffer[0] = 1.0f;
    equalizer.SetWetMix(0.0f);
    mixer.ProcessAudio(dryBuffer.data(), 64, 1, 48000);

    EXPECT_FLOAT_EQ(dryBuffer[0], 1.0f);
    EXPECT_TRUE(std::all_of(
        dryBuffer.begin() + 1,
        dryBuffer.end(),
        [](float sample) { return sample == 0.0f; }));

    std::vector<float> wetBuffer(64, 0.0f);
    wetBuffer[0] = 1.0f;
    equalizer.ResetState();
    equalizer.SetWetMix(1.0f);
    mixer.ProcessAudio(wetBuffer.data(), 64, 1, 48000);

    const bool changed = std::any_of(
        wetBuffer.begin(),
        wetBuffer.end(),
        [](float sample) { return std::abs(sample) > 1e-4f && sample != 1.0f; }) ||
        std::any_of(
            wetBuffer.begin() + 1,
            wetBuffer.end(),
            [](float sample) { return std::abs(sample) > 1e-5f; });
    EXPECT_TRUE(changed);
}

TEST(AudioMixer, ReverbationProducesAudibleTail) {
    AudioMixer mixer;
    Reverbation reverb;
    reverb.SetWetMix(1.0f);
    reverb.SetDryMix(0.0f);
    reverb.SetRoomSize(1.0f);
    reverb.SetDamping(0.0f);
    mixer.AddEffect(&reverb);

    std::vector<float> buffer(2000, 0.0f);
    buffer[0] = 1.0f;
    mixer.ProcessAudio(buffer.data(), 2000, 1, 48000);

    EXPECT_FLOAT_EQ(buffer[0], 0.0f);
    const bool hasTail = std::any_of(
        buffer.begin() + 1000,
        buffer.end(),
        [](float sample) { return std::abs(sample) > 1e-6f; });
    EXPECT_TRUE(hasTail);
}

TEST(AudioMixer, ReverbationWidthControlsStereoCrossfeed) {
    AudioMixer narrowMixer;
    Reverbation narrowReverb;
    narrowReverb.SetWetMix(1.0f);
    narrowReverb.SetDryMix(0.0f);
    narrowReverb.SetRoomSize(1.0f);
    narrowReverb.SetDamping(0.0f);
    narrowReverb.SetWidth(0.0f);
    narrowMixer.AddEffect(&narrowReverb);

    std::vector<float> narrowBuffer(2000 * 2, 0.0f);
    narrowBuffer[0] = 1.0f;
    narrowMixer.ProcessAudio(narrowBuffer.data(), 2000, 2, 48000);

    float narrowMaxDiff = 0.0f;
    for (size_t i = 1100; i < 1150; ++i) {
        narrowMaxDiff = std::max(
            narrowMaxDiff,
            std::abs(narrowBuffer[i * 2] - narrowBuffer[i * 2 + 1]));
    }
    EXPECT_LT(narrowMaxDiff, 1e-6f);

    AudioMixer wideMixer;
    Reverbation wideReverb;
    wideReverb.SetWetMix(1.0f);
    wideReverb.SetDryMix(0.0f);
    wideReverb.SetRoomSize(1.0f);
    wideReverb.SetDamping(0.0f);
    wideReverb.SetWidth(1.0f);
    wideMixer.AddEffect(&wideReverb);

    std::vector<float> wideBuffer(2000 * 2, 0.0f);
    wideBuffer[0] = 1.0f;
    wideMixer.ProcessAudio(wideBuffer.data(), 2000, 2, 48000);

    float wideMaxDiff = 0.0f;
    for (size_t i = 1100; i < 1150; ++i) {
        wideMaxDiff = std::max(
            wideMaxDiff,
            std::abs(wideBuffer[i * 2] - wideBuffer[i * 2 + 1]));
    }
    EXPECT_GT(wideMaxDiff, 1e-6f);
}

TEST(AudioMixer, FFTFilterAnalyzesWithoutMutatingBuffer) {
    AudioMixer mixer;
    FFTFilter fft(8);
    fft.SetSmoothingFactor(0.0f);
    mixer.AddEffect(&fft);

    std::vector<float> buffer = {1.0f, 0.5f, 0.0f, -0.5f};
    const std::vector<float> original = buffer;
    mixer.ProcessAudio(buffer.data(), 4, 1, 48000);

    EXPECT_EQ(buffer, original);
    ASSERT_EQ(fft.GetSpectrumSize(), 4u);
    const bool hasSpectrum = std::any_of(
        fft.GetSpectrumData(),
        fft.GetSpectrumData() + fft.GetSpectrumSize(),
        [](float value) { return value > 0.0f; });
    EXPECT_TRUE(hasSpectrum);
}

} // namespace