comparison base/AudioLevel.h @ 0:fc9323a41f5a

start base : Sonic Visualiser sv1-1.0rc1

+/* -*- 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
+