diff audio/PlaySpeedRangeMapper.cpp @ 468:56acd9368532 bqaudioio

Initial work toward switching to bqaudioio library (so as to get I/O, not just O)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/audio/PlaySpeedRangeMapper.cpp	Tue Aug 04 13:27:42 2015 +0100
@@ -0,0 +1,101 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Sonic Visualiser
+    An audio file viewer and annotation editor.
+    Centre for Digital Music, Queen Mary, University of London.
+    This file copyright 2006 QMUL.
+    
+    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.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#include "PlaySpeedRangeMapper.h"
+
+#include <iostream>
+#include <cmath>
+
+// PlaySpeedRangeMapper maps a position in the range [0,120] on to a
+// play speed factor on a logarithmic scale in the range 0.125 ->
+// 8. This ensures that the desirable speed factors 0.25, 0.5, 1, 2,
+// and 4 are all mapped to exact positions (respectively 20, 40, 60,
+// 80, 100).
+
+// Note that the "factor" referred to below is a play speed factor
+// (higher = faster, 1.0 = normal speed), the "value" is a percentage
+// (higher = faster, 100 = normal speed), and the "position" is an
+// integer step on the dial's scale (0-120, 60 = centre).
+
+PlaySpeedRangeMapper::PlaySpeedRangeMapper() :
+    m_minpos(0),
+    m_maxpos(120)
+{
+}
+
+int
+PlaySpeedRangeMapper::getPositionForValue(double value) const
+{
+    // value is percent
+    double factor = getFactorForValue(value);
+    int position = getPositionForFactor(factor);
+    return position;
+}
+
+int
+PlaySpeedRangeMapper::getPositionForValueUnclamped(double value) const
+{
+    // We don't really provide this
+    return getPositionForValue(value);
+}
+
+double
+PlaySpeedRangeMapper::getValueForPosition(int position) const
+{
+    double factor = getFactorForPosition(position);
+    double pc = getValueForFactor(factor);
+    return pc;
+}
+
+double
+PlaySpeedRangeMapper::getValueForPositionUnclamped(int position) const
+{
+    // We don't really provide this
+    return getValueForPosition(position);
+}
+
+double
+PlaySpeedRangeMapper::getValueForFactor(double factor) const
+{
+    return factor * 100.0;
+}
+
+double
+PlaySpeedRangeMapper::getFactorForValue(double value) const
+{
+    return value / 100.0;
+}
+
+int
+PlaySpeedRangeMapper::getPositionForFactor(double factor) const
+{
+    if (factor == 0) return m_minpos;
+    int pos = int(lrint((log2(factor) + 3.0) * 20.0));
+    if (pos < m_minpos) pos = m_minpos;
+    if (pos > m_maxpos) pos = m_maxpos;
+    return pos;
+}
+
+double
+PlaySpeedRangeMapper::getFactorForPosition(int position) const
+{
+    return pow(2.0, double(position) * 0.05 - 3.0);
+}
+
+QString
+PlaySpeedRangeMapper::getUnit() const
+{
+    return "%";
+}