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Fade effects gradually adjust the volume of audio clips over a specified duration.

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FadeIn

Gradually increases volume from 0 to the clip’s original volume over the specified duration. 
from movielite.afx import FadeIn

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Constructor

FadeIn(duration: float)
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duration
float
required
Duration of the fade in seconds, applied from the start of the clip. Must be a positive number.

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Methods

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apply

def apply(self, clip: AudioClip) -> None
Apply the fade in effect by adding a transform to the clip’s processing pipeline.
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clip
AudioClip
required
The AudioClip to apply the fade in effect to
Returns: None (modifies the clip in place)

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How It Works

The fade in effect:
  1. Calculates the fade period from clip.offset to clip.offset + duration
  2. Applies a linear fade factor to each audio sample during the fade period
  3. Leaves samples after the fade period unmodified
The fade factor increases linearly from 0 to 1:
  • At the start: fade_factor = 0 (silence)
  • At the end: fade_factor = 1 (original volume)

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Example

from movielite.audio import AudioClip
from movielite.afx import FadeIn

# Create an audio clip
clip = AudioClip("music.mp3")

# Apply a 3-second fade in from the start
fade = FadeIn(duration=3.0)
fade.apply(clip)
The fade is applied relative to the clip’s offset, not absolute timeline position.

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FadeOut

Gradually decreases volume from the clip’s original volume to 0 over the specified duration. 
from movielite.afx import FadeOut

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Constructor

FadeOut(duration: float)
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duration
float
required
Duration of the fade in seconds, applied at the end of the clip. Must be a positive number.

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Methods

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apply

def apply(self, clip: AudioClip) -> None
Apply the fade out effect by adding a transform to the clip’s processing pipeline.
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clip
AudioClip
required
The AudioClip to apply the fade out effect to
Returns: None (modifies the clip in place)

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How It Works

The fade out effect:
  1. Calculates the fade period from clip.offset + clip.duration - duration to clip.offset + clip.duration
  2. Applies a linear fade factor to each audio sample during the fade period
  3. Leaves samples before the fade period unmodified
The fade factor decreases linearly from 1 to 0:
  • At the start: fade_factor = 1 (original volume)
  • At the end: fade_factor = 0 (silence)

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Example

from movielite.audio import AudioClip
from movielite.afx import FadeOut

# Create an audio clip
clip = AudioClip("music.mp3")

# Apply a 2-second fade out at the end
fade = FadeOut(duration=2.0)
fade.apply(clip)
The fade is calculated from the end of the clip backwards by the specified duration.

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Combining Fade Effects

You can apply both fade in and fade out to the same clip: 
from movielite.audio import AudioClip
from movielite.afx import FadeIn, FadeOut

clip = AudioClip("background_music.mp3")

# Fade in over 2 seconds at the start
FadeIn(duration=2.0).apply(clip)

# Fade out over 3 seconds at the end
FadeOut(duration=3.0).apply(clip)
Both effects add transforms to the clip’s processing pipeline and work independently. The order of application doesn’t matter since they affect different parts of the clip.

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