scale.py

   1 #!/usr/bin/env python
   2 #
   3 # This file is part of jack_mixer
   4 #
   5 # Copyright (C) 2006 Nedko Arnaudov <nedko@arnaudov.name>
   6 #
   7 # This program is free software; you can redistribute it and/or modify
   8 # it under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation; version 2 of the License
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with this program; if not, write to the Free Software
  18 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19
  20 import math
  21 import fpconst
  22
  23 class threshold:
  24     '''Encapsulates scale linear function edge and coefficients for scale = a * dB + b formula'''
  25     def __init__(self, db, scale):
  26         self.db = db
  27         self.scale = scale
  28         self.text = "%.0f" % math.fabs(db)
  29
  30     def calculate_coefficients(self, prev):
  31         self.a = (prev.scale - self.scale) / (prev.db - self.db)
  32         self.b = self.scale - self.a * self.db
  33         #print "%.0f dB - %.0f dB: scale = %f * dB + %f" % (prev.db, self.db, self.a, self.b)
  34
  35     def db_to_scale(self, db):
  36         return self.a * db + self.b
  37
  38     def scale_to_db(self, scale):
  39         return (scale - self.b) / self.a
  40
  41 class base:
  42     '''Scale abstraction, various scale implementation derive from this class'''
  43     def __init__(self, scale_id, description):
  44         self.scale = []
  45         self.marks = []
  46         self.db_max = fpconst.NegInf
  47         self.scale_id = scale_id
  48         self.description = description
  49
  50     def add_threshold(self, db, scale, mark):
  51         thr = threshold(db, scale)
  52         self.scale.append(thr)
  53         if mark:
  54             self.marks.append(thr)
  55
  56     def add_mark(self, db):
  57         mark = threshold(db, -1.0)
  58         self.marks.append(mark)
  59         if db > self.db_max:
  60             self.db_max = db
  61
  62     def calculate_coefficients(self):
  63         prev = None
  64         for i in self.scale:
  65             if prev != None:
  66                 i.calculate_coefficients(prev)
  67             prev = i
  68
  69     def get_marks(self):
  70         return self.marks
  71
  72     def scale_marks(self):
  73         for i in self.marks:
  74             if i.scale == -1.0:
  75                 i.scale = self.db_to_scale(i.db)
  76
  77     def db_to_scale(self, db):
  78         '''Convert dBFS value to number in range 0.0-1.0 used in GUI'''
  79         prev = None
  80         for i in self.scale:
  81             if db < i.db:
  82                 #print "Match at %f dB treshold" % i.db
  83                 if prev == None:
  84                     return 0.0
  85                 return i.db_to_scale(db)
  86             prev = i
  87         return 1.0
  88
  89     def scale_to_db(self, scale):
  90         '''Convert number in range 0.0-1.0 used in GUI to dBFS value'''
  91         prev = None
  92         for i in self.scale:
  93             if scale <= i.scale:
  94                 if prev == None:
  95                     return fpconst.NegInf;
  96                 return i.scale_to_db(scale)
  97             prev = i
  98         return self.db_max
  99
 100 # IEC 60268-18 Peak programme level meters - Digital audio peak level meter
 101 # Adapted from meterpridge, may be wrong, I'm not buying standards, event if they cost $45
 102 # If someone has the standart, please eighter share it with me or fix the code.
 103 class iec_268(base):
 104     '''IEC 60268-18 Peak programme level meters - Digital audio peak level meter'''
 105     def __init__(self):
 106         base.__init__(self, "iec_268", "IEC 60268-18 Peak programme level meters - Digital audio peak level meter")
 107         self.add_threshold(-70.0, 0.0, False)
 108         self.add_threshold(-60.0, 0.05, True)
 109         self.add_threshold(-50.0, 0.075, True)
 110         self.add_threshold(-40.0, 0.15, True)
 111         self.add_mark(-35.0)
 112         self.add_threshold(-30.0, 0.3, True)
 113         self.add_mark(-25.0)
 114         self.add_threshold(-20.0, 0.5, True)
 115         self.add_mark(-15.0)
 116         self.add_mark(-10.0)
 117         self.add_mark(-5.0)
 118         self.add_threshold(0.0, 1.0, True)
 119         self.calculate_coefficients()
 120         self.scale_marks()
 121
 122 class linear_70dB(base):
 123     '''Linear scale with range from -70 to 0 dBFS'''
 124     def __init__(self):
 125         base.__init__(self, "linear_70dB", "Linear scale with range from -70 to 0 dBFS")
 126         self.add_threshold(-70.0, 0.0, False)
 127         self.add_mark(-60.0)
 128         self.add_mark(-50.0)
 129         self.add_mark(-40.0)
 130         self.add_mark(-35.0)
 131         self.add_mark(-30.0)
 132         self.add_mark(-25.0)
 133         self.add_mark(-20.0)
 134         self.add_mark(-15.0)
 135         self.add_mark(-10.0)
 136         self.add_mark(-5.0)
 137         self.add_threshold(0.0, 1.0, True)
 138         self.calculate_coefficients()
 139         self.scale_marks()
 140
 141 class linear_30dB(base):
 142     '''Linear scale with range from -30 to +30 dBFS'''
 143     def __init__(self):
 144         base.__init__(self, "linear_30dB", "Linear scale with range from -30 to +30 dBFS")
 145         self.add_threshold(-30.0, 0.0, False)
 146         self.add_threshold(+30.0, 1.0, True)
 147         self.calculate_coefficients()
 148         self.scale_marks()
 149
 150 def scale_test1(scale):
 151     for i in range(-97 * 2, 1, 1):
 152         db = float(i)/2.0
 153         print "%5.1f dB maps to %f" % (db, scale.db_to_scale(db))
 154
 155 def scale_test2(scale):
 156     for i in range(101):
 157         s = float(i)/100.0
 158         print "%.2f maps to %.1f dB" % (s, scale.scale_to_db(s))
 159
 160 def print_db_to_scale(db):
 161     print "%-.1f dB maps to %f" % (db, scale.db_to_scale(db))
 162
 163 def scale_test3(scale):
 164     print_db_to_scale(+77.0)
 165     print_db_to_scale(+7.0)
 166     print_db_to_scale(0.0)
 167     print_db_to_scale(-107.0)
 168
 169 #scale = linear_30dB()
 170 #scale_test2(scale)
 171 #scale_test3(scale)