Apply fade-in/out effect to input audio.

A description of the accepted parameters follows.

type, t

Specify the effect type, can be either in for fade-in, or out for a fade-out effect. Default is in.

start_sample, ss

Specify the number of the start sample for starting to apply the fade effect. Default is 0.

nb_samples, ns

Specify the number of samples for which the fade effect has to last. At the end of the fade-in effect the output audio will have the same volume as the input audio, at the end of the fade-out transition the output audio will be silence. Default is 44100.

start_time, st

Specify time for starting to apply the fade effect. Default is 0. The accepted syntax is:

[-]HH[:MM[:SS[.m...]]]
[-]S+[.m...]

See also the function av_parse_time(). If set this option is used instead of start_sample one.

duration, d

Specify the duration for which the fade effect has to last. Default is 0. The accepted syntax is:

[-]HH[:MM[:SS[.m...]]]
[-]S+[.m...]

See also the function av_parse_time(). At the end of the fade-in effect the output audio will have the same volume as the input audio, at the end of the fade-out transition the output audio will be silence. If set this option is used instead of nb_samples one.

curve

Set curve for fade transition.

It accepts the following values:

tri

select triangular, linear slope (default)

qsin

select quarter of sine wave

hsin

select half of sine wave

esin

select exponential sine wave

log

select logarithmic

par

select inverted parabola

qua

select quadratic

cub

select cubic

squ

select square root

cbr

select cubic root