comparison audioio/PlaySpeedRangeMapper.cpp @ 59:1016a8ceceda

* Introduce PlaySpeedRangeMapper for playback speed dial

+/* -*- 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 Chris Cannam.
+    
+    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>
+
+
+PlaySpeedRangeMapper::PlaySpeedRangeMapper(int minpos, int maxpos) :
+    m_minpos(minpos),
+    m_maxpos(maxpos)
+{
+}
+
+int
+PlaySpeedRangeMapper::getPositionForValue(float value) const
+{
+    // value is percent
+
+    float factor = getFactorForValue(value);
+
+    bool slow = (factor > 1.0);
+
+    if (!slow) factor = 1.0 / factor;
+    
+    int half = (m_maxpos + m_minpos) / 2;
+
+    factor = sqrtf((factor - 1.0) * 1000.f);
+    int position = lrintf(((factor * (half - m_minpos)) / 100.0) + m_minpos);
+
+    if (slow) {
+        position = half - position;
+    } else {
+        position = position + half;
+    }
+
+//    std::cerr << "value = " << value << " slow = " << slow << " factor = " << factor << " position = " << position << std::endl;
+
+    return position;
+}
+
+float
+PlaySpeedRangeMapper::getValueForPosition(int position) const
+{
+    float factor = getFactorForPosition(position);
+    float pc;
+    if (factor < 1.0) pc = ((1.0 / factor) - 1.0) * 100.0;
+    else pc = (1.0 - factor) * 100.0;
+//    std::cerr << "position = " << position << " percent = " << pc << std::endl;
+    return pc;
+}
+
+float
+PlaySpeedRangeMapper::getFactorForValue(float value) const
+{
+    // value is percent
+    
+    float factor;
+
+    if (value <= 0) {
+        factor = 1.0 - (value / 100.0);
+    } else {
+        factor = 1.0 / (1.0 + (value / 100.0));
+    }
+
+//    std::cerr << "value = " << value << " factor = " << factor << std::endl;
+    return factor;
+}
+
+float
+PlaySpeedRangeMapper::getFactorForPosition(int position) const
+{
+    bool slow = false;
+
+    if (position < m_minpos) position = m_minpos;
+    if (position > m_maxpos) position = m_maxpos;
+
+    int half = (m_maxpos + m_minpos) / 2;
+
+    if (position < half) {
+        slow = true;
+        position = half - position;
+    } else {
+        position = position - half;
+    }
+
+    // position is between min and half (inclusive)
+
+    float factor;
+
+    if (position == m_minpos) {
+        factor = 1.0;
+    } else {
+        factor = ((position - m_minpos) * 100.0) / (half - m_minpos);
+        factor = 1.0 + (factor * factor) / 1000.f;
+    }
+
+    if (!slow) factor = 1.0 / factor;
+
+//    std::cerr << "position = " << position << " slow = " << slow << " factor = " << factor << std::endl;
+
+    return factor;
+}
+
+QString
+PlaySpeedRangeMapper::getUnit() const
+{
+    return "%";
+}