annotate base/AudioLevel.h @ 492:23945cdd7161

* Update RDF query stuff again so as to set up a temporary datastore
  each time we want to query over an rdf file, instead of using rasqal
  against the file.  Seems the only way to avoid threading and storage
  management issues when trying to load from a single-source file and
  perform queries against our main datastore at the same time.  Maybe.

/* -*- 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 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.
*/

/*
   This is a modified version of a source file from the 
   Rosegarden MIDI and audio sequencer and notation editor.
   This file copyright 2000-2006 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