view base/AudioLevel.h @ 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.
*/

#ifndef _AUDIO_LEVEL_H_
#define _AUDIO_LEVEL_H_

/**
 * AudioLevel converts audio sample levels between various scales:
 *
 *   - dB values (-inf -> 0dB)
 *   - floating-point values (-1.0 -> 1.0) such as used for a
 *     multiplier for gain or in floating-point WAV files
 *   - integer values intended to correspond to pixels on a fader
 *     or vu level scale.
 */

class AudioLevel
{
public:

    static const float DB_FLOOR;

    enum FaderType {
	     ShortFader = 0, // -40 -> +6  dB
              LongFader = 1, // -70 -> +10 dB
            IEC268Meter = 2, // -70 ->  0  dB
        IEC268LongMeter = 3, // -70 -> +10 dB (0dB aligns with LongFader)
	   PreviewLevel = 4
    };

    static float multiplier_to_dB(float multiplier);
    static float dB_to_multiplier(float dB);

    static float fader_to_dB(int level, int maxLevel, FaderType type);
    static int   dB_to_fader(float dB, int maxFaderLevel, FaderType type);

    static float fader_to_multiplier(int level, int maxLevel, FaderType type);
    static int   multiplier_to_fader(float multiplier, int maxFaderLevel,
				     FaderType type);

    // fast if "levels" doesn't change often -- for audio segment previews
    static int   multiplier_to_preview(float multiplier, int levels);
    static float preview_to_multiplier(int level, int levels);
};


#endif