Implement Gain parameter for Sampler and Synth

* Add Gain parameter (-30 dB to +30 dB) to SamplerDevice and SynthDevice
* Add Gain knobs to Synth and Sampler dialogs
* Update Knob component to support dB formatting
* Add unit tests for gain functionality and XML serialization

Author: juzzlin

CHANGELOG

@@ -5,6 +5,10 @@ Release date:
 
 New features:
 
+* Implement a Gain parameter for Noteahead Sampler and Synth
+  - Range: -30 dB to +30 dB
+  - Allows proper gain staging when recording alongside hardware instruments
+
 * Fix GitHub Issue #45: Implement a simple built-in sampler
 
 * Implements a virtual device rack

src/application/service/sampler_controller.cpp

@@ -154,6 +154,38 @@ void SamplerController::setSelectedPadHpfCutoff(double cutoff)
     }
 }
 
+double SamplerController::globalVolume() const
+{
+    if (!m_sampler) {
+        return 1.0;
+    }
+    return static_cast<double>(m_sampler->globalVolume());
+}
+
+void SamplerController::setGlobalVolume(double volume)
+{
+    if (m_sampler) {
+        m_sampler->setGlobalVolume(static_cast<float>(volume));
+        emit globalVolumeChanged();
+    }
+}
+
+double SamplerController::gain() const
+{
+    if (!m_sampler) {
+        return 0.5;
+    }
+    return static_cast<double>(m_sampler->gain());
+}
+
+void SamplerController::setGain(double gain)
+{
+    if (m_sampler) {
+        m_sampler->setGain(static_cast<float>(gain));
+        emit gainChanged();
+    }
+}
+
 int SamplerController::selectedPadStartOffsetSeconds() const
 {
     if (!m_sampler || m_selectedPad < 0) {
@@ -243,6 +275,8 @@ void SamplerController::initialize()
         emit selectedPadStartOffsetChanged();
         emit selectedPadDurationChanged();
     }
+    emit globalVolumeChanged();
+    emit gainChanged();
     emit channelModeChanged();
 }
 
@@ -255,6 +289,8 @@ void SamplerController::reset()
         emit selectedPadCutoffChanged();
         emit selectedPadHpfCutoffChanged();
         emit selectedPadStartOffsetChanged();
+        emit globalVolumeChanged();
+        emit gainChanged();
         emit channelModeChanged();
     }
 }

src/application/service/sampler_controller.hpp

@@ -37,6 +37,8 @@ class SamplerController : public QObject
     Q_PROPERTY(double selectedPadVolume READ selectedPadVolume WRITE setSelectedPadVolume NOTIFY selectedPadVolumeChanged)
     Q_PROPERTY(double selectedPadCutoff READ selectedPadCutoff WRITE setSelectedPadCutoff NOTIFY selectedPadCutoffChanged)
     Q_PROPERTY(double selectedPadHpfCutoff READ selectedPadHpfCutoff WRITE setSelectedPadHpfCutoff NOTIFY selectedPadHpfCutoffChanged)
+    Q_PROPERTY(double globalVolume READ globalVolume WRITE setGlobalVolume NOTIFY globalVolumeChanged)
+    Q_PROPERTY(double gain READ gain WRITE setGain NOTIFY gainChanged)
     Q_PROPERTY(int selectedPadStartOffsetSeconds READ selectedPadStartOffsetSeconds WRITE setSelectedPadStartOffsetSeconds NOTIFY selectedPadStartOffsetChanged)
     Q_PROPERTY(int selectedPadStartOffsetMilliseconds READ selectedPadStartOffsetMilliseconds WRITE setSelectedPadStartOffsetMilliseconds NOTIFY selectedPadStartOffsetChanged)
     Q_PROPERTY(double selectedPadDuration READ selectedPadDuration NOTIFY selectedPadDurationChanged)
@@ -72,6 +74,12 @@ class SamplerController : public QObject
     double selectedPadHpfCutoff() const;
     void setSelectedPadHpfCutoff(double cutoff);
 
+    double globalVolume() const;
+    void setGlobalVolume(double volume);
+
+    double gain() const;
+    void setGain(double gain);
+
     int selectedPadStartOffsetSeconds() const;
     void setSelectedPadStartOffsetSeconds(int seconds);
 
@@ -104,6 +112,8 @@ class SamplerController : public QObject
     void selectedPadVolumeChanged();
     void selectedPadCutoffChanged();
     void selectedPadHpfCutoffChanged();
+    void globalVolumeChanged();
+    void gainChanged();
     void selectedPadStartOffsetChanged();
     void selectedPadDurationChanged();
     void channelModeChanged();

src/application/service/synth_controller.cpp

@@ -137,6 +137,8 @@ int SynthController::masterPan() const { return m_synth ? static_cast<int>(std::
 void SynthController::setMasterPan(int p) { if (m_synth) { m_synth->setMasterPan(p / 1000.0f); emit masterPanChanged(); } }
 int SynthController::masterVolume() const { return m_synth ? static_cast<int>(std::round(m_synth->masterVolume() * 1000.0f)) : 0; }
 void SynthController::setMasterVolume(int v) { if (m_synth) { m_synth->setMasterVolume(v / 1000.0f); emit masterVolumeChanged(); } }
+int SynthController::gain() const { return m_synth ? static_cast<int>(std::round(m_synth->gain() * 1000.0f)) : 0; }
+void SynthController::setGain(int g) { if (m_synth) { m_synth->setGain(g / 1000.0f); emit gainChanged(); } }
 
 uint32_t SynthController::sampleRate() const { return m_synth ? m_synth->sampleRate() : static_cast<uint32_t>(Constants::defaultSampleRate()); }
 
@@ -232,7 +234,7 @@ void SynthController::requestSettings() {
     emit ampAttackChanged(); emit ampDecayChanged(); emit ampSustainChanged(); emit ampReleaseChanged();
     emit modAttackChanged(); emit modDecayChanged(); emit modIntChanged(); emit modTargetChanged();
     emit lfoWaveformChanged(); emit lfoModeChanged(); emit lfoRateChanged(); emit lfoIntChanged(); emit lfoTargetChanged();
-    emit voiceModeChanged(); emit voiceDepthChanged(); emit portamentoChanged(); emit panSpreadChanged(); emit masterPanChanged(); emit masterVolumeChanged();
+    emit voiceModeChanged(); emit voiceDepthChanged(); emit portamentoChanged(); emit panSpreadChanged(); emit masterPanChanged(); emit masterVolumeChanged(); emit gainChanged();
     emit delayTypeChanged(); emit delayTimeChanged(); emit delayFeedbackChanged(); emit delayDepthChanged(); emit delayMixChanged(); emit delaySyncChanged(); emit delaySyncDivisionChanged(); emit delayFeedbackLpfChanged(); emit delayFeedbackHpfChanged();
 }
 void SynthController::accept() {}

src/application/service/synth_controller.hpp

@@ -86,6 +86,7 @@ class SynthController : public QObject
     Q_PROPERTY(int panSpread READ panSpread WRITE setPanSpread NOTIFY panSpreadChanged)
     Q_PROPERTY(int masterPan READ masterPan WRITE setMasterPan NOTIFY masterPanChanged)
     Q_PROPERTY(int masterVolume READ masterVolume WRITE setMasterVolume NOTIFY masterVolumeChanged)
+    Q_PROPERTY(int gain READ gain WRITE setGain NOTIFY gainChanged)
     Q_PROPERTY(uint32_t sampleRate READ sampleRate NOTIFY sampleRateChanged)
     Q_PROPERTY(QStringList presetNames READ presetNames CONSTANT)
     Q_PROPERTY(int currentBank READ currentBank WRITE setCurrentBank NOTIFY currentBankChanged)
@@ -157,6 +158,7 @@ class SynthController : public QObject
     int panSpread() const; void setPanSpread(int s);
     int masterPan() const; void setMasterPan(int p);
     int masterVolume() const; void setMasterVolume(int v);
+    int gain() const; void setGain(int g);
 
     uint32_t sampleRate() const;
     Q_INVOKABLE float cutoffToHz(float cutoff) const;
@@ -201,7 +203,7 @@ class SynthController : public QObject
     void ampAttackChanged(); void ampDecayChanged(); void ampSustainChanged(); void ampReleaseChanged();
     void modAttackChanged(); void modDecayChanged(); void modIntChanged(); void modTargetChanged();
     void lfoWaveformChanged(); void lfoModeChanged(); void lfoRateChanged(); void lfoIntChanged(); void lfoTargetChanged();
-    void voiceModeChanged(); void voiceDepthChanged(); void portamentoChanged(); void panSpreadChanged(); void masterPanChanged(); void masterVolumeChanged();
+    void voiceModeChanged(); void voiceDepthChanged(); void portamentoChanged(); void panSpreadChanged(); void masterPanChanged(); void masterVolumeChanged(); void gainChanged();
     void sampleRateChanged();
     void delayTypeChanged(); void delayTimeChanged(); void delayFeedbackChanged(); void delayDepthChanged(); void delayMixChanged(); void delaySyncChanged(); void delaySyncDivisionChanged(); void delayFeedbackLpfChanged(); void delayFeedbackHpfChanged();
 

src/common/constants.cpp

@@ -649,6 +649,11 @@ QString xmlKeyVolume()
     return "volume";
 }
 
+QString xmlKeyGain()
+{
+    return "gain";
+}
+
 QString xmlKeyProject()
 {
     return "Project";

src/common/constants.hpp

@@ -195,6 +195,7 @@ QString xmlKeyValue();
 
 QString xmlKeyVelocity();
 QString xmlKeyVolume();
+QString xmlKeyGain();
 
 QString xmlKeyProject();
 QString xmlKeySong();

src/domain/devices/sampler_device.cpp

@@ -44,11 +44,17 @@ SamplerDevice::SamplerDevice(std::string name, AudioFileReaderU audioFileReader)
   , m_audioFileReader { audioFileReader ? std::move(audioFileReader) : std::make_unique<SndFileReader>() }
 {
     addParameter(Parameter { Constants::NahdXml::xmlKeyChannelMode().toStdString(), 0.0f, 0, 1, 0, 1 });
+    addParameter(Parameter { Constants::NahdXml::xmlKeyVolume().toStdString(), 1.0f, 0, 100, 100, 1 });
+    addParameter(Parameter { Constants::NahdXml::xmlKeyGain().toStdString(), 0.5f, -30, 30, 0, 1, false });
 
     m_voices.resize(m_maxVoices);
     for (auto && sample : m_samples) {
         sample = nullptr;
     }
+
+    m_manualGain = m_gain;
+    m_manualGlobalVolume = m_globalVolume;
+    syncParameters();
 }
 
 SamplerDevice::~SamplerDevice() = default;
@@ -153,6 +159,7 @@ void SamplerDevice::processMidiCc(uint8_t controller, uint8_t value, uint8_t cha
         if (controller == 121) { // Reset All Controllers
             m_globalPan = m_manualGlobalPan;
             m_globalVolume = m_manualGlobalVolume;
+            m_gain = m_manualGain;
             m_globalCutoff = m_manualGlobalCutoff;
             m_globalHpfCutoff = m_manualGlobalHpfCutoff;
 
@@ -170,6 +177,9 @@ void SamplerDevice::processMidiCc(uint8_t controller, uint8_t value, uint8_t cha
                 }
             }
 
+            if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) p->get().setValue(m_globalVolume);
+            if (auto p = parameter(Constants::NahdXml::xmlKeyGain().toStdString()); p) p->get().setValue(m_gain);
+
             for (auto && voice : m_voices) {
                 if (voice.active && voice.sample) {
                     voice.pan = m_globalPan;
@@ -226,6 +236,7 @@ void SamplerDevice::processMidiCc(uint8_t controller, uint8_t value, uint8_t cha
                 }
             } else if (controller == 7) { // Volume
                 m_globalVolume = static_cast<float>(value) / 127.0f;
+                if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) p->get().setValue(m_globalVolume);
                 // Update all active voices' volume
                 for (auto && voice : m_voices) {
                     if (voice.active) {
@@ -360,8 +371,8 @@ void SamplerDevice::processAudio(float * output, uint32_t nFrames, uint32_t samp
                 }
             }
 
-            output[i * 2] += left;
-            output[i * 2 + 1] += right;
+            output[i * 2] += left * m_linearGain;
+            output[i * 2 + 1] += right * m_linearGain;
 
             voice.position += pitchScale;
         }
@@ -380,9 +391,7 @@ void SamplerDevice::reset()
             voice.active = false;
         }
 
-        if (auto p = parameter(Constants::NahdXml::xmlKeyChannelMode().toStdString()); p) {
-            m_channelMode = p->get().value() > 0.5f;
-        }
+        syncParameters();
     }
 
     emit dataChanged();
@@ -770,9 +779,7 @@ void SamplerDevice::deserializeFromXml(QXmlStreamReader & reader)
     {
         std::lock_guard<std::mutex> lock { m_mutex };
         // Sync global fields
-        if (auto p = parameter(Constants::NahdXml::xmlKeyChannelMode().toStdString()); p) {
-            m_channelMode = p->get().value() > 0.5f;
-        }
+        syncParameters();
     }
 
     emit dataChanged();
@@ -808,4 +815,62 @@ void SamplerDevice::setProjectPath(const std::string & projectPath)
     m_projectPath = projectPath;
 }
 
+float SamplerDevice::globalVolume() const
+{
+    return m_globalVolume;
+}
+
+void SamplerDevice::setGlobalVolume(float volume)
+{
+    bool changed = false;
+    {
+        std::lock_guard<std::mutex> lock { m_mutex };
+        if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) {
+            p->get().setValue(volume);
+            m_manualGlobalVolume = p->get().value();
+            syncParameters();
+            changed = true;
+        }
+    }
+    if (changed) {
+        emit dataChanged();
+    }
+}
+
+float SamplerDevice::gain() const
+{
+    return m_gain;
+}
+
+void SamplerDevice::setGain(float gain)
+{
+    bool changed = false;
+    {
+        std::lock_guard<std::mutex> lock { m_mutex };
+        if (auto p = parameter(Constants::NahdXml::xmlKeyGain().toStdString()); p) {
+            p->get().setValue(gain);
+            m_manualGain = p->get().value();
+            syncParameters();
+            changed = true;
+        }
+    }
+    if (changed) {
+        emit dataChanged();
+    }
+}
+
+void SamplerDevice::syncParameters()
+{
+    if (auto p = parameter(Constants::NahdXml::xmlKeyChannelMode().toStdString()); p) {
+        m_channelMode = p->get().value() > 0.5f;
+    }
+    if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) {
+        m_globalVolume = p->get().value();
+    }
+    if (auto p = parameter(Constants::NahdXml::xmlKeyGain().toStdString()); p) {
+        m_gain = p->get().value();
+        m_linearGain = std::pow(10.0f, ((m_gain - 0.5f) * 60.0f) / 20.0f);
+    }
+}
+
 } // namespace noteahead

src/domain/devices/sampler_device.hpp

@@ -108,6 +108,12 @@ class SamplerDevice : public Device
     bool channelMode() const;
     void setChannelMode(bool enabled);
 
+    float globalVolume() const;
+    void setGlobalVolume(float volume);
+
+    float gain() const;
+    void setGain(float gain);
+
     double playbackPosition(uint8_t note) const;
     bool isFinished(uint8_t note) const;
 
@@ -119,6 +125,7 @@ class SamplerDevice : public Device
 private:
     struct Voice;
     void updateVoiceEffects(Voice & voice);
+    void syncParameters();
 
     struct Voice
     {
@@ -152,10 +159,13 @@ class SamplerDevice : public Device
     std::string m_name;
     float m_globalPan = 0.5f;
     float m_globalVolume = 1.0f;
+    float m_gain = 0.5f;
+    float m_linearGain = 1.0f;
     float m_globalCutoff = 1.0f;
     float m_globalHpfCutoff = 0.0f;
     float m_manualGlobalPan = 0.5f;
     float m_manualGlobalVolume = 1.0f;
+    float m_manualGain = 0.5f;
     float m_manualGlobalCutoff = 1.0f;
     float m_manualGlobalHpfCutoff = 0.0f;
     bool m_channelMode = false;

src/domain/devices/synth_device.cpp

@@ -118,6 +118,7 @@ SynthDevice::SynthDevice(std::string name)
     addParameter(Parameter { Constants::NahdXml::xmlKeyPanSpread().toStdString(), 0.0f, 0, 100, 0 });
     addParameter(Parameter { Constants::NahdXml::xmlKeyPan().toStdString(), 0.5f, 0, 100, 50 });
     addParameter(Parameter { Constants::NahdXml::xmlKeyVolume().toStdString(), 1.0f, 0, 100, 100 });
+    addParameter(Parameter { Constants::NahdXml::xmlKeyGain().toStdString(), 0.5f, -30, 30, 0, 1, false });
 
     addParameter(Parameter { Constants::NahdXml::xmlKeyDelayType().toStdString(), 0.0f, 0, 5, 0, 1, true });
     addParameter(Parameter { Constants::NahdXml::xmlKeyDelayTime().toStdString(), 0.5f, 0, 10000, 500 }); // 0..10 seconds in ms
@@ -137,6 +138,7 @@ SynthDevice::SynthDevice(std::string name)
     m_manualPanSpread = m_panSpread;
     m_manualMasterPan = m_masterPan;
     m_manualMasterVolume = m_masterVolume;
+    m_manualGain = m_gain;
     m_manualLpfCutoff = m_lpfCutoff;
     m_manualHpfCutoff = m_hpfCutoff;
 
@@ -246,9 +248,9 @@ void SynthDevice::processAudio(float * output, uint32_t nFrames, uint32_t sample
             voice.hpf.setCutoff(m_hpfCutoff);
 
             const float filtered { voice.hpf.process(voice.lpf.process(static_cast<float>(mixHeadroom))) };
-            const float finalSample { filtered * static_cast<float>(ampEnv) * m_masterVolume * (1.0f / static_cast<float>(MaxVoices)) };
+            const float finalSample { filtered * static_cast<float>(ampEnv) * m_masterVolume * (1.0f / static_cast<float>(MaxVoices)) * m_linearGain };
 
-            localBuffer[i * 2] += finalSample * (1.0f - voice.pan) * (1.0f - m_masterPan) * 2.0f;
+            localBuffer[i * 2] += finalSample * (1.0f - voice.pan);
             localBuffer[i * 2 + 1] += finalSample * voice.pan * m_masterPan * 2.0f;
         }
 
@@ -291,12 +293,14 @@ void SynthDevice::processMidiCc(uint8_t controller, uint8_t value, uint8_t)
             m_panSpread = m_manualPanSpread;
             m_masterPan = m_manualMasterPan;
             m_masterVolume = m_manualMasterVolume;
+            m_gain = m_manualGain;
             m_lpfCutoff = m_manualLpfCutoff;
             m_hpfCutoff = m_manualHpfCutoff;
 
             if (auto p = parameter(Constants::NahdXml::xmlKeyPanSpread().toStdString()); p) p->get().setValue(m_panSpread);
             if (auto p = parameter(Constants::NahdXml::xmlKeyPan().toStdString()); p) p->get().setValue(m_masterPan);
             if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) p->get().setValue(m_masterVolume);
+            if (auto p = parameter(Constants::NahdXml::xmlKeyGain().toStdString()); p) p->get().setValue(m_gain);
             if (auto p = parameter(Constants::NahdXml::xmlKeySynthLpfCutoff().toStdString()); p) p->get().setValue(m_lpfCutoff);
             if (auto p = parameter(Constants::NahdXml::xmlKeySynthHpfCutoff().toStdString()); p) p->get().setValue(m_hpfCutoff);
 
@@ -515,6 +519,10 @@ void SynthDevice::syncParameters()
     if (auto p = parameter(Constants::NahdXml::xmlKeyPanSpread().toStdString()); p) m_panSpread = p->get().value();
     if (auto p = parameter(Constants::NahdXml::xmlKeyPan().toStdString()); p) m_masterPan = p->get().value();
     if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) m_masterVolume = p->get().value();
+    if (auto p = parameter(Constants::NahdXml::xmlKeyGain().toStdString()); p) {
+        m_gain = p->get().value();
+        m_linearGain = std::pow(10.0f, ((m_gain - 0.5f) * 60.0f) / 20.0f);
+    }
 
     if (auto p = parameter(Constants::NahdXml::xmlKeyDelayType().toStdString()); p) m_delayType = static_cast<DelayEffect::Type>(p->get().xmlValue());
     if (auto p = parameter(Constants::NahdXml::xmlKeyDelayTime().toStdString()); p) m_delayTime = p->get().value() * 10.0f; 
@@ -751,6 +759,8 @@ float SynthDevice::masterPan() const { return m_masterPan; }
 void SynthDevice::setMasterPan(float pan) { bool changed = false; { std::lock_guard<std::mutex> lock { m_mutex }; if (auto p = parameter(Constants::NahdXml::xmlKeyPan().toStdString()); p) { p->get().setValue(pan); m_manualMasterPan = p->get().value(); syncParameters(); changed = true; } } if (changed) emit dataChanged(); }
 float SynthDevice::masterVolume() const { return m_masterVolume; }
 void SynthDevice::setMasterVolume(float vol) { bool changed = false; { std::lock_guard<std::mutex> lock { m_mutex }; if (auto p = parameter(Constants::NahdXml::xmlKeyVolume().toStdString()); p) { p->get().setValue(vol); m_manualMasterVolume = p->get().value(); syncParameters(); changed = true; } } if (changed) emit dataChanged(); }
+float SynthDevice::gain() const { return m_gain; }
+void SynthDevice::setGain(float val) { bool changed = false; { std::lock_guard<std::mutex> lock { m_mutex }; if (auto p = parameter(Constants::NahdXml::xmlKeyGain().toStdString()); p) { p->get().setValue(val); m_manualGain = p->get().value(); syncParameters(); changed = true; } } if (changed) emit dataChanged(); }
 
 // Delay Accessors
 DelayEffect::Type SynthDevice::delayType() const { return m_delayType; }