view base/AudioLevel.cpp @ 6:44bbf5793d84

* Rework handling of layer properties in file I/O -- we now get the individual
  layers to load and save them rather than doing it via generic property lists
  in the base class, so as to ensure we read and write meaningful values rather
  than generic int values requiring conversion.

/* -*- 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, 2005-2006
    
    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];
}