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/DelayFilter.cpp

@@ -0,0 +1,112 @@
+/*
+	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 <cmath>
+
+#include "helpers/MemoryHelper.h"
+#include "DelayFilter.h"
+
+using namespace std;
+
+DelayFilter::DelayFilter(double delay, bool isMs)
+	:delay(delay), isMs(isMs)
+{
+	buffers = NULL;
+}
+
+DelayFilter::~DelayFilter()
+{
+	cleanup();
+}
+
+vector<wstring> DelayFilter::initialize(float sampleRate, unsigned maxFrameCount, vector<wstring> channelNames)
+{
+	cleanup();
+
+	channelCount = (unsigned)channelNames.size();
+
+	if(isMs)
+		bufferLength = (unsigned)(sampleRate * delay / 1000.0 + 0.5);
+	else
+		bufferLength = (unsigned)(delay + 0.5);
+
+	buffers = (float**)MemoryHelper::alloc(sizeof(float*) * channelCount);
+
+	for(unsigned i=0; i<channelCount; i++)
+	{
+		buffers[i] = (float*)MemoryHelper::alloc(sizeof(float) * bufferLength);
+		memset(buffers[i], 0, sizeof(float) * bufferLength);
+	}
+
+	bufferOffset = 0;
+
+	return channelNames;
+}
+
+#pragma AVRT_CODE_BEGIN
+void DelayFilter::process(float** output, float** input, unsigned frameCount)
+{
+	for(unsigned i=0; i<channelCount; i++)
+	{
+		float* inputChannel = input[i];
+		float* outputChannel = output[i];
+		float* bufferChannel = buffers[i];
+
+		if(bufferLength <= frameCount)
+		{
+			memcpy(outputChannel, bufferChannel + bufferOffset, (bufferLength - bufferOffset) * sizeof(float));
+			memcpy(outputChannel + bufferLength - bufferOffset, bufferChannel, bufferOffset * sizeof(float));
+			memcpy(outputChannel + bufferLength, inputChannel, (frameCount - bufferLength) * sizeof(float));
+			memcpy(bufferChannel, inputChannel + frameCount - bufferLength, bufferLength * sizeof(float));
+		}
+		else
+		{
+			if(bufferLength < bufferOffset + frameCount)
+			{
+				memcpy(outputChannel, bufferChannel + bufferOffset, (bufferLength - bufferOffset) * sizeof(float));
+				memcpy(outputChannel + bufferLength - bufferOffset, bufferChannel, (frameCount - (bufferLength - bufferOffset)) * sizeof(float));
+				memcpy(bufferChannel + bufferOffset, inputChannel, (bufferLength - bufferOffset) * sizeof(float));
+				memcpy(bufferChannel, inputChannel + bufferLength - bufferOffset, (frameCount - (bufferLength - bufferOffset)) * sizeof(float));
+			}
+			else
+			{
+				memcpy(outputChannel, bufferChannel + bufferOffset, frameCount * sizeof(float));
+				memcpy(bufferChannel + bufferOffset, inputChannel, frameCount * sizeof(float));
+			}
+		}
+	}
+
+	if(bufferLength <= frameCount)
+		bufferOffset = 0;
+	else
+		bufferOffset = (bufferOffset + frameCount) % bufferLength;
+}
+#pragma AVRT_CODE_END
+
+void DelayFilter::cleanup()
+{
+	if(buffers != NULL)
+	{
+		for(unsigned i=0; i<channelCount; i++)
+			MemoryHelper::free(buffers[i]);
+
+		MemoryHelper::free(buffers);
+		buffers = NULL;
+	}
+}