music_sampler/music_effect.py

   1 class GainEffect:
   2     effect_types = [
   3         'noop',
   4         'fade'
   5     ]
   6
   7     def __init__(self, effect, audio_segment, initial_loop, start, end,
   8             **kwargs):
   9         if effect in self.effect_types:
  10             self.effect = effect
  11         else:
  12             self.effect = 'noop'
  13
  14         self.start = start
  15         self.end = end
  16         self.audio_segment = audio_segment
  17         self.initial_loop = initial_loop
  18         getattr(self, self.effect + "_init")(**kwargs)
  19
  20     def get_last_gain(self):
  21         return getattr(self, self.effect + "_get_last_gain")()
  22
  23     def get_next_gain(self, current_frame, current_loop, frame_count):
  24         # This returns two values:
  25         # - The first one is the gain to apply on that frame
  26         # - The last one is True or False depending on whether it is the last
  27         #   call to the function and the last gain should be saved permanently
  28         return getattr(self, self.effect + "_get_next_gain")(
  29                 current_frame,
  30                 current_loop,
  31                 frame_count)
  32
  33     # Noop
  34     def noop_init(self, **kwargs):
  35         pass
  36
  37     def noop_get_last_gain(self, **kwargs):
  38         return 0
  39
  40     def noop_get_next_gain(self, **kwargs):
  41         return [0, True]
  42
  43     # Fading
  44     def fade_init(self, gain=0, **kwargs):
  45         self.audio_segment_frame_count = self.audio_segment.frame_count()
  46         self.first_frame = int(
  47                 self.audio_segment_frame_count * self.initial_loop +\
  48                 self.audio_segment.frame_rate * self.start)
  49         self.last_frame = int(
  50                 self.audio_segment_frame_count * self.initial_loop +\
  51                 self.audio_segment.frame_rate * self.end)
  52         self.gain= gain
  53
  54     def fade_get_last_gain(self):
  55         return self.gain
  56
  57     def fade_get_next_gain(self, current_frame, current_loop, frame_count):
  58         current_frame = current_frame \
  59                 + (current_loop - self.initial_loop) \
  60                     * self.audio_segment_frame_count
  61
  62         if current_frame >= self.last_frame:
  63             return [self.gain, True]
  64         elif current_frame < self.first_frame:
  65             return [0, False]
  66         else:
  67             return [
  68                     (current_frame - self.first_frame) / \
  69                             (self.last_frame - self.first_frame) * self.gain,
  70                     False
  71                     ]
  72
  73