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.

filters/ChannelFilterFactory.cpp

@@ -0,0 +1,64 @@
+/*
+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.
+*/
+
+#include "helpers/MemoryHelper.h"
+#include "helpers/StringHelper.h"
+#include "helpers/LogHelper.h"
+#include "ChannelFilter.h"
+#include "ChannelFilterFactory.h"
+
+using namespace std;
+
+vector<IFilter*> ChannelFilterFactory::createFilter(const wstring& configPath, wstring& command, wstring& parameters)
+{
+	ChannelFilter* filter = NULL;
+
+	if(command == L"Channel")
+	{
+		wstring value = parameters + L" ";
+
+		vector<wstring> words;
+		wstring currentWord;
+		for(unsigned i=0; i<value.length(); i++)
+		{
+			wchar_t c = towupper(value[i]);
+
+			if(c == L' ')
+			{
+				if(currentWord.length() > 0)
+				{
+					words.push_back(currentWord);
+
+					currentWord.clear();
+				}
+			}
+			else
+			{
+				currentWord += c;
+			}
+		}
+
+		void* mem = MemoryHelper::alloc(sizeof(ChannelFilter));
+		filter = new(mem) ChannelFilter(words);
+	}
+
+	if(filter == NULL)
+		return vector<IFilter*>(0);
+	return vector<IFilter*>(1, filter);
+}