Do 5Hz high pass filter to clean up any DC offset created by the model

CMakeLists.txt

@@ -22,11 +22,13 @@ set(NAM_LV2_ID http://github.com/mikeoliphant/neural-amp-modeler-lv2)
 
 include_directories(SYSTEM deps/eigen)
 include_directories(SYSTEM deps/lv2/include)
-include_directories(SYSTEM deps/NeuralAmpModelerCore/NAM)
+include_directories(SYSTEM deps/NeuralAmpModelerCore)
+include_directories(SYSTEM deps/NeuralAmpModelerCore)
 include_directories(SYSTEM deps/json)
 include_directories(SYSTEM deps/denormal)
 
 add_definitions(-DNAM_SAMPLE_FLOAT)
+add_definitions(-DDSP_SAMPLE_FLOAT)
 
 add_subdirectory(src)
 

src/CMakeLists.txt

@@ -17,10 +17,16 @@ set(NAM_SOURCES	../deps/NeuralAmpModelerCore/NAM/activations.h
 	../deps/NeuralAmpModelerCore/NAM/convnet.cpp
 	../deps/NeuralAmpModelerCore/NAM/convnet.h)
 
-add_library(neural_amp_modeler MODULE ${SOURCES} ${NAM_SOURCES})
+set(DSP_SOURCES	../deps/NeuralAmpModelerCore/dsp/dsp.h
+	../deps/NeuralAmpModelerCore/dsp/dsp.cpp
+	../deps/NeuralAmpModelerCore/dsp/RecursiveLinearFilter.h
+	../deps/NeuralAmpModelerCore/dsp/RecursiveLinearFilter.cpp)
+
+add_library(neural_amp_modeler MODULE ${SOURCES} ${NAM_SOURCES} ${DSP_SOURCES})
 
 source_group(TREE ${CMAKE_CURRENT_SOURCE_DIR} FILES ${SOURCES})
 source_group(NAM ${CMAKE_CURRENT_SOURCE_DIR} FILES ${NAM_SOURCES})
+source_group(dsp ${CMAKE_CURRENT_SOURCE_DIR} FILES ${DSP_SOURCES})
 
 option(DISABLE_DENORMALS "Disable floating point denormals" ON)
 

src/nam_plugin.cpp

@@ -1,10 +1,10 @@
 #include <algorithm>
 #include <cmath>
 #include <utility>
+#include <cassert>
 
 #include "nam_plugin.h"
-#include "activations.h"
-#include <cassert>
+#include <NAM/activations.h>
 
 #define SMOOTH_EPSILON .0001f
 
@@ -20,8 +20,14 @@ namespace NAM {
 		delete currentModel;
 	}
 
-	bool Plugin::initialize(double rate, const LV2_Feature* const* features) noexcept
+	bool Plugin::initialize(double sampleRate, const LV2_Feature* const* features) noexcept
 	{
+		this->sampleRate = sampleRate;
+
+		const double highPassCutoffFreq = 5.0;
+		const recursive_linear_filter::HighPassParams highPassParams(sampleRate, highPassCutoffFreq);
+		mHighPass.SetParams(highPassParams);
+
 		// for fetching initial options, can be null
 		LV2_Options_Option* options = nullptr;
 
@@ -243,10 +249,15 @@ namespace NAM {
 			}
 		}
 
+		float** outputPtrs = &ports.audio_out;
+
 		if (currentModel != nullptr)
 		{
 			currentModel->process(&ports.audio_out, &ports.audio_out, 1, n_samples, 1.0, 1.0, mNAMParams);
 			currentModel->finalize_(n_samples);
+
+			// Apply a high pass filter at 5Hz to eliminate any DC offset
+			outputPtrs = mHighPass.Process(outputPtrs, 1, n_samples);
 		}
 
 		// convert output level from db
@@ -259,7 +270,7 @@ namespace NAM {
 				// do very basic smoothing
 				outputLevel = (.99f * outputLevel) + (.01f * desiredOutputLevel);
 
-				ports.audio_out[i] *= outputLevel;
+				ports.audio_out[i] = outputPtrs[0][i] * outputLevel;
 			}
 		}
 		else
@@ -268,7 +279,7 @@ namespace NAM {
 
 			for (unsigned int i = 0; i < n_samples; i++)
 			{
-				ports.audio_out[i] *= outputLevel;
+				ports.audio_out[i] = outputPtrs[0][i] * outputLevel;
 			}
 		}
 	}

src/nam_plugin.h

@@ -21,7 +21,8 @@
 #include <lv2/state/state.h>
 #include <lv2/units/units.h>
 
-#include "dsp.h"
+#include <NAM/dsp.h>
+#include <dsp/RecursiveLinearFilter.h>
 
 #define PlUGIN_URI "http://github.com/mikeoliphant/neural-amp-modeler-lv2"
 #define MODEL_URI PlUGIN_URI "#model"
@@ -64,12 +65,15 @@ namespace NAM {
 
 		Ports ports = {};
 
+		double sampleRate;
+
 		LV2_URID_Map* map = nullptr;
 		LV2_Log_Logger logger = {};
 		LV2_Worker_Schedule* schedule = nullptr;
 
 		::DSP* currentModel = nullptr;
 		std::string currentModelPath;
+		recursive_linear_filter::HighPass mHighPass;
 
 		std::unordered_map<std::string, double> mNAMParams = {};