Apply fade-in/out effect to input video.

It accepts the parameters: type:start_frame:nb_frames[:options]

type specifies if the effect type, can be either "in" for fade-in, or "out" for a fade-out effect.

start_frame specifies the number of the start frame for starting to apply the fade effect.

nb_frames specifies the number of frames for which the fade effect has to last. At the end of the fade-in effect the output video will have the same intensity as the input video, at the end of the fade-out transition the output video will be completely black.

options is an optional sequence of key=value pairs, separated by ":". The description of the accepted options follows.

type, t

See type.

start_frame, s

See start_frame.

nb_frames, n

See nb_frames.

alpha

If set to 1, fade only alpha channel, if one exists on the input. Default value is 0.

A few usage examples follow, usable too as test scenarios.

# fade in first 30 frames of video
fade=in:0:30

# fade out last 45 frames of a 200-frame video
fade=out:155:45

# fade in first 25 frames and fade out last 25 frames of a 1000-frame video
fade=in:0:25, fade=out:975:25

# make first 5 frames black, then fade in from frame 5-24
fade=in:5:20

# fade in alpha over first 25 frames of video
fade=in:0:25:alpha=1