helpers/music_effect.py

   1 class GainEffect:
   2     effect_types = [
   3         'fade'
   4     ]
   5
   6     def __init__(self, effect, audio_segment, start, end, **kwargs):
   7         if effect in self.effect_types:
   8             self.effect = effect
   9         else:
  10             raise Exception("Unknown effect {}".format(effect))
  11
  12         self.start = start
  13         self.end = end
  14         self.audio_segment = audio_segment
  15         getattr(self, self.effect + "_init")(**kwargs)
  16
  17     def get_last_gain(self):
  18         return getattr(self, self.effect + "_get_last_gain")()
  19
  20     def get_next_gain(self, current_frame, frame_count):
  21         # This returns two values:
  22         # - The first one is the gain to apply on that frame
  23         # - The last one is True or False depending on whether it is the last
  24         #   call to the function and the last gain should be saved permanently
  25         return getattr(self, self.effect + "_get_next_gain")(
  26                 current_frame,
  27                 frame_count)
  28
  29     # Fading
  30     def fade_init(self, gain=0, **kwargs):
  31         self.first_frame = int(self.audio_segment.frame_rate * self.start)
  32         self.last_frame = int(self.audio_segment.frame_rate * self.end)
  33         self.gain= gain
  34
  35     def fade_get_last_gain(self):
  36         return self.gain
  37
  38     def fade_get_next_gain(self, current_frame, frame_count):
  39         if current_frame >= self.last_frame:
  40             return [self.gain, True]
  41         elif current_frame < self.first_frame:
  42             return [0, False]
  43         else:
  44             return [
  45                     (current_frame - self.first_frame) / \
  46                             (self.last_frame - self.first_frame) * self.gain,
  47                     False
  48                     ]
  49
  50