Merge pull request #94 from mikeoliphant/smart_bypass

README.md

@@ -58,4 +58,6 @@ After building, the plugin will be in **build/neural_amp_modeler.lv2**.
 
 ```-DUSE_NATIVE_ARCH=ON```: If you have a relatively modern x64 processor, you can pass ```-DUSE_NATIVE_ARCH=ON``` on your cmake command line to enable certain processor-specific optimizations.
 
+```-DSMART_BYPASS_ENABLED=ON```: If enabled, this will bypass model processing if input has been silent (below -100 dB by default) for a sufficient number of samples (determined by the model's receptive field size).
+
 Also see the [NeuralAudio CMake options](https://github.com/mikeoliphant/NeuralAudio#cmake-options) - adding these to your neural-amp-modeler-lv2 cmake will pass them to the NeuralAudio build.

src/CMakeLists.txt

@@ -54,6 +54,12 @@ if (DISABLE_DENORMALS)
 	add_definitions(-DDISABLE_DENORMALS)
 endif (DISABLE_DENORMALS)
 
+option(SMART_BYPASS_ENABLED "Enable auto-bypass on silence" OFF)
+
+if (SMART_BYPASS_ENABLED)
+	add_definitions(-DSMART_BYPASS_ENABLED)
+endif (SMART_BYPASS_ENABLED)
+
 set_target_properties(neural_amp_modeler
 	PROPERTIES
 	CXX_VISIBILITY_PRESET hidden

src/nam_plugin.cpp

@@ -7,12 +7,18 @@
 
 #define SMOOTH_EPSILON .0001f
 
+#ifndef BYPASS_DB_THRESHOLD
+#define BYPASS_DB_THRESHOLD -100
+#endif
+
 namespace NAM {
 	Plugin::Plugin()
 	{
 		// prevent allocations on the audio thread
 		currentModelPath.reserve(MAX_FILE_NAME + 1);
 
+		bypassThresholdLinear = powf(10, BYPASS_DB_THRESHOLD * 0.05f);
+
 //		NeuralAudio::NeuralModel::SetLSTMLoadMode(
 //#ifdef LSTM_PREFER_NAM
 //			NeuralAudio::PreferNAMCore
@@ -181,6 +187,18 @@ namespace NAM {
 		nam->currentModelPath = msg->path;
 		assert(nam->currentModelPath.capacity() >= MAX_FILE_NAME + 1);
 
+		if (nam->currentModel != nullptr)
+		{
+			int receptiveFieldSize = nam->currentModel->GetReceptiveFieldSize();
+
+			if (receptiveFieldSize > -1)
+			{
+				// A newly loaded model is prewarmed to have a silent sample history
+				nam->silentSamples = receptiveFieldSize;
+				nam->smartBypassed = true;
+			}
+		}
+
 		// send reply
 		nam->schedule->schedule_work(nam->schedule->handle, sizeof(reply), &reply);
 
@@ -241,6 +259,44 @@ namespace NAM {
 		if (currentModel != nullptr)
 		{
 			modelInputAdjustmentDB = currentModel->GetRecommendedInputDBAdjustment();
+
+#ifdef SMART_BYPASS_ENABLED
+			int receptiveFieldSamples = currentModel->GetReceptiveFieldSize();
+
+			if (receptiveFieldSamples > -1)
+			{
+				for (unsigned int i = 0; i < n_samples; i++)
+				{
+					if (abs(ports.audio_in[i]) <= bypassThresholdLinear)
+					{
+						silentSamples++;
+					}
+					else
+					{
+						silentSamples = 0;
+					}
+				}
+
+				if (silentSamples >= (uint32_t)receptiveFieldSamples)
+				{
+					silentSamples = (uint32_t)receptiveFieldSamples;	// Prevent silentSamples growing and eventually overflowing uint32
+
+					if (smartBypassed)
+					{
+						for (unsigned int i = 0; i < n_samples; i++)
+						{
+							ports.audio_out[i] = ports.audio_in[i];
+						}
+
+						return;
+					}
+
+					smartBypassed = true; // If we aren't already, we'll be bypassed on the next process call
+				}
+				else
+					smartBypassed = false;
+			}
+#endif
 		}
 
 		// convert input level from db

src/nam_plugin.h

@@ -80,6 +80,7 @@ namespace NAM {
 
 		bool initialize(double rate, const LV2_Feature* const* features) noexcept;
 		void set_max_buffer_size(int size) noexcept;
+		void activate() noexcept;
 		void process(uint32_t n_samples) noexcept;
 
 		void write_current_path();
@@ -120,5 +121,8 @@ namespace NAM {
 		float inputLevel = 0;
 		float outputLevel = 0;
 		int32_t maxBufferSize = 512;
+		float bypassThresholdLinear = 0;
+		uint32_t silentSamples = 0;
+		bool smartBypassed = true;
 	};
 }