gtk2_ardour/logmeter.h

   1 /*
   2     Copyright (C) 2000-2007 Paul Davis
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17
  18 */
  19
  20 #ifndef __ardour_gtk_log_meter_h__
  21 #define __ardour_gtk_log_meter_h__
  22
  23 #if 1
  24 static inline float
  25 _log_meter (float power, double lower_db, double upper_db, double non_linearity)
  26 {
  27         return (power < lower_db ? 0.0 : pow((power-lower_db)/(upper_db-lower_db), non_linearity));
  28 }
  29
  30 static inline float
  31 alt_log_meter (float power)
  32 {
  33         return _log_meter (power, -192.0, 0.0, 8.0);
  34 }
  35 #endif
  36
  37 inline float
  38 log_meter (float db)
  39 {
  40          gfloat def = 0.0f; /* Meter deflection %age */
  41
  42          if (db < -70.0f) {
  43                  def = 0.0f;
  44          } else if (db < -60.0f) {
  45                  def = (db + 70.0f) * 0.25f;
  46          } else if (db < -50.0f) {
  47                  def = (db + 60.0f) * 0.5f + 2.5f;
  48          } else if (db < -40.0f) {
  49                  def = (db + 50.0f) * 0.75f + 7.5f;
  50          } else if (db < -30.0f) {
  51                  def = (db + 40.0f) * 1.5f + 15.0f;
  52          } else if (db < -20.0f) {
  53                  def = (db + 30.0f) * 2.0f + 30.0f;
  54          } else if (db < 6.0f) {
  55                  def = (db + 20.0f) * 2.5f + 50.0f;
  56          } else {
  57                  def = 115.0f;
  58          }
  59
  60          /* 115 is the deflection %age that would be
  61             when db=6.0. this is an arbitrary
  62             endpoint for our scaling.
  63          */
  64
  65          return def/115.0f;
  66 }
  67
  68 #endif /* __ardour_gtk_log_meter_h__ */