Remove the Gate knob from effects (#8011)

Major changes:
- Remove Gate knob from effects, effectively hard coding its value to zero
- Replace effect RMS calculations with a more efficient way of detecting silent buffers
- Only perform silent buffer detection when `ProcessStatus::ContinueIfNotQuiet` is returned from a plugin AND auto-quit is enabled

Minor changes:
- Remove gate from presets
- Remove gate from .mmp projects
- Move `Effect::processorCount()` to `LadspaEffect`
- Rename `Effect::checkGate` to `Effect::handleAutoQuit`
- Adjust silence threshold for better compatibility with old RMS calculations
- Remove some unnecessary methods from `Effect`
- Reset quiet buffer count in `stopRunning`
- Use positive name for auto-quit boolean
- Simplify `m_autoQuitEnabled` initialization

include/Effect.h

@@ -26,10 +26,12 @@
 #ifndef LMMS_EFFECT_H
 #define LMMS_EFFECT_H
 
-#include "Plugin.h"
-#include "Engine.h"
+#include <span>
+
 #include "AudioEngine.h"
 #include "AutomatableModel.h"
+#include "Engine.h"
+#include "Plugin.h"
 #include "TempoSyncKnobModel.h"
 
 namespace lmms
@@ -66,16 +68,6 @@ public:
 	//! Returns true if audio was processed and should continue being processed
 	bool processAudioBuffer(SampleFrame* buf, const fpp_t frames);
 
-	inline ch_cnt_t processorCount() const
-	{
-		return m_processors;
-	}
-
-	inline void setProcessorCount( ch_cnt_t _processors )
-	{
-		m_processors = _processors;
-	}
-
 	inline bool isOkay() const
 	{
 		return m_okay;
@@ -92,14 +84,15 @@ public:
 		return m_running;
 	}
 
-	inline void startRunning() 
-	{ 
-		m_bufferCount = 0;
-		m_running = true; 
+	void startRunning()
+	{
+		m_quietBufferCount = 0;
+		m_running = true;
 	}
 
-	inline void stopRunning()
+	void stopRunning()
 	{
+		m_quietBufferCount = 0;
 		m_running = false;
 	}
 
@@ -124,27 +117,6 @@ public:
 		return 1.0f - m_wetDryModel.value();
 	}
 
-	inline float gate() const
-	{
-		const float level = m_gateModel.value();
-		return level*level * m_processors;
-	}
-
-	inline f_cnt_t bufferCount() const
-	{
-		return m_bufferCount;
-	}
-
-	inline void resetBufferCount()
-	{
-		m_bufferCount = 0;
-	}
-
-	inline void incrementBufferCount()
-	{
-		++m_bufferCount;
-	}
-
 	inline bool dontRun() const
 	{
 		return m_noRun;
@@ -160,6 +132,11 @@ public:
 		return &m_autoQuitModel;
 	}
 
+	bool autoQuitEnabled() const
+	{
+		return m_autoQuitEnabled;
+	}
+
 	EffectChain * effectChain() const
 	{
 		return m_parent;
@@ -227,11 +204,11 @@ protected:
 
 private:
 	/**
-		If the setting "Keep effects running even without input" is disabled,
-		after "decay" ms of a signal below "gate", the effect is turned off
-		and won't be processed again until it receives new audio input
-	*/
-	void checkGate(double outSum);
+	 * If auto-quit is enabled ("Keep effects running even without input" setting is disabled),
+	 * after "decay" ms of the output buffer remaining below the silence threshold, the effect is
+	 * turned off and won't be processed again until it receives new audio input.
+	 */
+	void handleAutoQuit(std::span<const SampleFrame> output);
 
 
 	EffectChain * m_parent;
@@ -240,19 +217,18 @@ private:
 					SampleFrame* _dst_buf, sample_rate_t _dst_sr,
 					const f_cnt_t _frames );
 
-	ch_cnt_t m_processors;
-
 	bool m_okay;
 	bool m_noRun;
 	bool m_running;
-	f_cnt_t m_bufferCount;
+
+	//! The number of consecutive periods where output buffers remain below the silence threshold
+	f_cnt_t m_quietBufferCount = 0;
 
 	BoolModel m_enabledModel;
 	FloatModel m_wetDryModel;
-	FloatModel m_gateModel;
 	TempoSyncKnobModel m_autoQuitModel;
-	
-	bool m_autoQuitDisabled;
+
+	bool m_autoQuitEnabled = false;
 
 	SRC_DATA m_srcData[2];
 	SRC_STATE * m_srcState[2];

include/EffectView.h

@@ -92,7 +92,6 @@ private:
 	LedCheckBox * m_bypass;
 	Knob * m_wetDry;
 	TempoSyncKnob * m_autoQuit;
-	Knob * m_gate;
 	QMdiSubWindow * m_subWindow;
 	EffectControlDialog * m_controlView;