Version 0.9

Added: Filter type "IIR", which allows to specify a user-defined IIR filter of arbitrary order with custom coefficients.
Improved: For playback devices, the APO is now installed both as GFX (post-mix) and LFX (pre-mix) APO. Normally the filtering happens in GFX, but the command "Stage" allows to select LFX to apply effects based on the number of input channels.
Added: Expression language. The commands "If", "ElseIf", "Else", "EndIf", "Eval" and inline expressions allow to change the filter behaviour based on runtime conditions.
Added: Command "Copy", which copies audio data between channels.
Added: Command "Delay", which delays the audio on the currently selected channels.
Improved: Configuration files are now locked exclusively for writing while reading them.
Improved: There is now a transition (10 ms) from old to new configuration after loading.
Improved: Substantial internal restructuring to improve extensibility and maintainability. Filtering commands now work exactly in the order they were specified.
Fixed: When the microphone input was in stereo but the application requested a mono stream, the audio was heavily distorted.
Fixed: The sine sweep generated by the Benchmark application had floating-point precision issues leading to severe artifacts when certain filters were applied.

FilterEngine.h

@@ -0,0 +1,111 @@
+/*
+	This file is part of EqualizerAPO, a system-wide equalizer.
+	Copyright (C) 2014  Jonas Thedering
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License along
+	with this program; if not, write to the Free Software Foundation, Inc.,
+	51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+#include <string>
+#include <vector>
+#include <hash_map>
+#include <hash_set>
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <mpParser.h>
+
+#include "IFilterFactory.h"
+#include "FilterConfiguration.h"
+#include "helpers/PrecisionTimer.h"
+#include "helpers/MemoryHelper.h"
+
+#pragma AVRT_VTABLES_BEGIN
+class FilterEngine
+{
+public:
+	FilterEngine();
+	~FilterEngine();
+
+	void setLfx(bool lfx);
+	void setDeviceInfo(bool capture, const std::wstring& deviceName, const std::wstring& connectionName, const std::wstring& deviceGuid);
+	void initialize(float sampleRate, unsigned inputChannelCount, unsigned realChannelCount, unsigned outputChannelCount, unsigned channelMask, unsigned maxFrameCount);
+	void loadConfig();
+	void loadConfig(const std::wstring& path);
+	void watchRegistryKey(const std::wstring& key);
+	void process(float *output, float *input, unsigned frameCount);
+
+	bool isLfx() const {return lfx;}
+	bool isCapture() const {return capture;}
+	std::wstring getDeviceName() const {return deviceName;}
+	std::wstring getConnectionName() const {return connectionName;}
+	std::wstring getDeviceGuid() const {return deviceGuid;}
+	unsigned getInputChannelCount() const {return inputChannelCount;}
+	unsigned getRealChannelCount() const {return realChannelCount;}
+	unsigned getOutputChannelCount() const {return outputChannelCount;}
+	unsigned getChannelMask() const {return channelMask;}
+	float getSampleRate() const {return sampleRate;}
+	unsigned getMaxFrameCount() const {return maxFrameCount;}
+	mup::ParserX* getParser() {return &parser;}
+
+private:
+	void addFilters(std::vector<IFilter*> filters);
+	void cleanupConfigurations();
+	static unsigned long __stdcall notificationThread(void* parameter);
+
+	std::vector<IFilterFactory*> factories;
+
+	bool lfx;
+	bool capture;
+	std::wstring deviceName;
+	std::wstring connectionName;
+	std::wstring deviceGuid;
+	std::wstring configPath;
+	float sampleRate;
+	// number of input channels that originally existed before child APO processing
+	unsigned inputChannelCount;
+	// number of input channels in process (including channels coming from child APO output)
+	unsigned realChannelCount;
+	unsigned outputChannelCount;
+	unsigned channelMask;
+	unsigned maxFrameCount;
+
+	// only used during loading
+	std::vector<FilterInfo*> filterInfos;
+	std::vector<std::wstring> currentChannelNames;
+	std::vector<std::wstring> lastChannelNames;
+	std::vector<std::wstring> lastNewChannelNames;
+	std::vector<std::wstring> allChannelNames;
+	bool lastInPlace;
+	mup::ParserX parser;
+
+	FilterConfiguration* currentConfig;
+	FilterConfiguration* nextConfig;
+	FilterConfiguration* previousConfig;
+
+	unsigned transitionCounter;
+	unsigned transitionLength;
+	HANDLE loadSemaphore;
+	CRITICAL_SECTION loadSection;
+	PrecisionTimer timer;
+	void* threadHandle;
+	void* shutdownEvent;
+	stdext::hash_set<std::wstring> watchRegistryKeys;
+	bool lastInputWasSilent;
+	unsigned lastInputSize;
+	stdext::hash_map<std::wstring, int> channelNameToPosMap;
+	stdext::hash_map<int, std::wstring> channelPosToNameMap;
+};
+#pragma AVRT_VTABLES_END