comparison base/AudioLevel.cpp @ 0:da6937383da8

initial import

+/* -*- c-basic-offset: 4 -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    A waveform viewer and audio annotation editor.
+    Chris Cannam, Queen Mary University of London, 2005
+    
+    This is experimental software.  Not for distribution.
+*/
+
+/*
+   This is a modified version of a source file from the 
+   Rosegarden MIDI and audio sequencer and notation editor.
+   This file copyright 2000-2005 Chris Cannam.
+*/
+
+#include "base/AudioLevel.h"
+#include <cmath>
+#include <iostream>
+#include <map>
+#include <vector>
+#include <cassert>
+
+const float AudioLevel::DB_FLOOR = -1000.0;
+
+struct FaderDescription
+{
+    FaderDescription(float _minDb, float _maxDb, float _zeroPoint) :
+	minDb(_minDb), maxDb(_maxDb), zeroPoint(_zeroPoint) { }
+
+    float minDb;
+    float maxDb;
+    float zeroPoint; // as fraction of total throw
+};
+
+static const FaderDescription faderTypes[] = {
+    FaderDescription(-40.0,  +6.0, 0.75), // short
+    FaderDescription(-70.0, +10.0, 0.80), // long
+    FaderDescription(-70.0,   0.0, 1.00), // IEC268
+    FaderDescription(-70.0, +10.0, 0.80), // IEC268 long
+    FaderDescription(-40.0,   0.0, 1.00), // preview
+};
+
+typedef std::vector<float> LevelList;
+static std::map<int, LevelList> previewLevelCache;
+static const LevelList &getPreviewLevelCache(int levels);
+
+float
+AudioLevel::multiplier_to_dB(float multiplier)
+{
+    if (multiplier == 0.0) return DB_FLOOR;
+    float dB = 10 * log10f(multiplier);
+    return dB;
+}
+
+float
+AudioLevel::dB_to_multiplier(float dB)
+{
+    if (dB == DB_FLOOR) return 0.0;
+    float m = powf(10.0, dB / 10.0);
+    return m;
+}
+
+/* IEC 60-268-18 fader levels.  Thanks to Steve Harris. */
+
+static float iec_dB_to_fader(float db)
+{
+    float def = 0.0f; // Meter deflection %age
+
+    if (db < -70.0f) {
+        def = 0.0f;
+    } else if (db < -60.0f) {
+        def = (db + 70.0f) * 0.25f;
+    } else if (db < -50.0f) {
+        def = (db + 60.0f) * 0.5f + 5.0f;
+    } else if (db < -40.0f) {
+        def = (db + 50.0f) * 0.75f + 7.5f;
+    } else if (db < -30.0f) {
+        def = (db + 40.0f) * 1.5f + 15.0f;
+    } else if (db < -20.0f) {
+        def = (db + 30.0f) * 2.0f + 30.0f;
+    } else {
+        def = (db + 20.0f) * 2.5f + 50.0f;
+    }
+
+    return def;
+}
+
+static float iec_fader_to_dB(float def)  // Meter deflection %age
+{
+    float db = 0.0f;
+
+    if (def >= 50.0f) {
+	db = (def - 50.0f) / 2.5f - 20.0f;
+    } else if (def >= 30.0f) {
+	db = (def - 30.0f) / 2.0f - 30.0f;
+    } else if (def >= 15.0f) {
+	db = (def - 15.0f) / 1.5f - 40.0f;
+    } else if (def >= 7.5f) {
+	db = (def - 7.5f) / 0.75f - 50.0f;
+    } else if (def >= 5.0f) {
+	db = (def - 5.0f) / 0.5f - 60.0f;
+    } else {
+	db = (def / 0.25f) - 70.0f;
+    }
+
+    return db;
+}
+
+float
+AudioLevel::fader_to_dB(int level, int maxLevel, FaderType type)
+{
+    if (level == 0) return DB_FLOOR;
+
+    if (type == IEC268Meter || type == IEC268LongMeter) {
+
+	float maxPercent = iec_dB_to_fader(faderTypes[type].maxDb);
+	float percent = float(level) * maxPercent / float(maxLevel);
+	float dB = iec_fader_to_dB(percent);
+	return dB;
+
+    } else { // scale proportional to sqrt(fabs(dB))
+
+	int zeroLevel = int(maxLevel * faderTypes[type].zeroPoint);
+    
+	if (level >= zeroLevel) {
+	    
+	    float value = level - zeroLevel;
+	    float scale = float(maxLevel - zeroLevel) /
+		sqrtf(faderTypes[type].maxDb);
+	    value /= scale;
+	    float dB = powf(value, 2.0);
+	    return dB;
+	    
+	} else {
+	    
+	    float value = zeroLevel - level;
+	    float scale = zeroLevel / sqrtf(0.0 - faderTypes[type].minDb);
+	    value /= scale;
+	    float dB = powf(value, 2.0);
+	    return 0.0 - dB;
+	}
+    }
+}
+
+
+int
+AudioLevel::dB_to_fader(float dB, int maxLevel, FaderType type)
+{
+    if (dB == DB_FLOOR) return 0;
+
+    if (type == IEC268Meter || type == IEC268LongMeter) {
+
+	// The IEC scale gives a "percentage travel" for a given dB
+	// level, but it reaches 100% at 0dB.  So we want to treat the
+	// result not as a percentage, but as a scale between 0 and
+	// whatever the "percentage" for our (possibly >0dB) max dB is.
+	
+	float maxPercent = iec_dB_to_fader(faderTypes[type].maxDb);
+	float percent = iec_dB_to_fader(dB);
+	int faderLevel = int((maxLevel * percent) / maxPercent + 0.01);
+	
+	if (faderLevel < 0) faderLevel = 0;
+	if (faderLevel > maxLevel) faderLevel = maxLevel;
+	return faderLevel;
+
+    } else {
+
+	int zeroLevel = int(maxLevel * faderTypes[type].zeroPoint);
+
+	if (dB >= 0.0) {
+	    
+	    float value = sqrtf(dB);
+	    float scale = (maxLevel - zeroLevel) / sqrtf(faderTypes[type].maxDb);
+	    value *= scale;
+	    int level = int(value + 0.01) + zeroLevel;
+	    if (level > maxLevel) level = maxLevel;
+	    return level;
+	    
+	} else {
+
+	    dB = 0.0 - dB;
+	    float value = sqrtf(dB);
+	    float scale = zeroLevel / sqrtf(0.0 - faderTypes[type].minDb);
+	    value *= scale;
+	    int level = zeroLevel - int(value + 0.01);
+	    if (level < 0) level = 0;
+	    return level;
+	}
+    }
+}
+
+	
+float
+AudioLevel::fader_to_multiplier(int level, int maxLevel, FaderType type)
+{
+    if (level == 0) return 0.0;
+    return dB_to_multiplier(fader_to_dB(level, maxLevel, type));
+}
+
+int
+AudioLevel::multiplier_to_fader(float multiplier, int maxLevel, FaderType type)
+{
+    if (multiplier == 0.0) return 0;
+    float dB = multiplier_to_dB(multiplier);
+    int fader = dB_to_fader(dB, maxLevel, type);
+    return fader;
+}
+
+
+const LevelList &
+getPreviewLevelCache(int levels)
+{
+    LevelList &ll = previewLevelCache[levels];
+    if (ll.empty()) {
+	for (int i = 0; i <= levels; ++i) {
+	    float m = AudioLevel::fader_to_multiplier
+		(i + levels/4, levels + levels/4, AudioLevel::PreviewLevel);
+	    if (levels == 1) m /= 100; // noise
+	    ll.push_back(m);
+	}
+    }
+    return ll;
+}
+
+int
+AudioLevel::multiplier_to_preview(float m, int levels)
+{
+    assert(levels > 0);
+    if (m < 0.0) return -multiplier_to_preview(-m, levels);
+
+    const LevelList &ll = getPreviewLevelCache(levels);
+    int result = -1;
+
+    int lo = 0, hi = levels;
+
+    // binary search
+    int level = -1;
+    while (result < 0) {
+	int newlevel = (lo + hi) / 2;
+	if (newlevel == level ||
+	    newlevel == 0 ||
+	    newlevel == levels) {
+	    result = newlevel;
+	    break;
+	}
+	level = newlevel;
+	if (ll[level] >= m) {
+	    hi = level;
+	} else if (ll[level+1] >= m) {
+	    result = level;
+	} else {
+	    lo = level;
+	}
+    }
+		   
+    return result;
+}
+
+float
+AudioLevel::preview_to_multiplier(int level, int levels)
+{
+    assert(levels > 0);
+    if (level < 0) return -preview_to_multiplier(-level, levels);
+    const LevelList &ll = getPreviewLevelCache(levels);
+    return ll[level];
+}
+	
+