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.

IFilter.cpp

@@ -0,0 +1,65 @@
+/*
+	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 <algorithm>
+
+#include "helpers/LogHelper.h"
+#include "IFilter.h"
+
+using namespace std;
+
+int IFilter::getChannelIndex(std::wstring word, const std::vector<std::wstring>& channelNames, bool allowNew)
+{
+	int channelIndex = -1;
+
+	if(iswdigit(word[0]))
+	{
+		channelIndex = wcstol(word.c_str(), NULL, 10) - 1;
+
+		if(channelIndex < 0 || channelIndex >= (int)channelNames.size())
+		{
+			LogF(L"Channel number %s out of range (1 - %d)", word.c_str(), channelNames.size());
+			channelIndex = -1;
+		}
+	}
+	else
+	{
+		vector<wstring>::const_iterator pos = find(channelNames.begin(), channelNames.end(), word);
+
+		if(pos == channelNames.end())
+		{
+			//Special handling to accept "wrong", but unambiguous positions
+			if(word == L"SL")
+				pos = find(channelNames.begin(), channelNames.end(), L"RL");
+			else if(word == L"SR")
+				pos = find(channelNames.begin(), channelNames.end(), L"RR");
+			else if(word == L"RL")
+				pos = find(channelNames.begin(), channelNames.end(), L"SL");
+			else if(word == L"RR")
+				pos = find(channelNames.begin(), channelNames.end(), L"SR");
+		}
+
+		if(pos != channelNames.end())
+			channelIndex = (int)(pos - channelNames.begin());
+		else if(!allowNew)
+			LogF(L"Invalid channel position %s", word.c_str());
+	}
+
+	return channelIndex;
+}