Added: Loudness correction filter by Alexander Walch that adjusts shelving filters based on the system volume. Also includes a GUI that allows calibration using a test sound.

Editor/helpers/QtSndfileHandle.cpp

@@ -0,0 +1,66 @@
+/*
+    This file is part of Equalizer APO, a system-wide equalizer.
+    Copyright (C) 2017  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 "QtSndfileHandle.h"
+
+sf_count_t getFileLenDevice(void* user_data)
+{
+	QIODevice* device = (QIODevice*)user_data;
+	return device->size();
+}
+
+sf_count_t seekDevice(sf_count_t offset, int whence, void* user_data)
+{
+	QIODevice* device = (QIODevice*)user_data;
+	qint64 pos;
+	if (whence == SF_SEEK_SET)
+		pos = 0;
+	else if (whence == SF_SEEK_CUR)
+		pos = device->pos();
+	else // whence == SF_SEEK_END
+		pos = device->size();
+	if (!device->seek(pos + offset))
+		return -1;
+	return device->pos();
+}
+
+sf_count_t readDevice(void* ptr, sf_count_t count, void* user_data)
+{
+	QIODevice* device = (QIODevice*)user_data;
+	return device->read((char*)ptr, count);
+}
+
+sf_count_t writeDevice(const void* ptr, sf_count_t count, void* user_data)
+{
+	QIODevice* device = (QIODevice*)user_data;
+	return device->write((const char*)ptr, count);
+}
+
+sf_count_t tellDevice(void* user_data)
+{
+	QIODevice* device = (QIODevice*)user_data;
+	return device->pos();
+}
+
+SF_VIRTUAL_IO g_deviceIo = {getFileLenDevice, seekDevice, readDevice, writeDevice, tellDevice};
+
+QtSndfileHandle::QtSndfileHandle(QIODevice& device, int mode, int format, int channels, int samplerate)
+	: SndfileHandle(g_deviceIo, &device, mode, format, channels, samplerate)
+{
+}