afftfilt
Apply arbitrary expressions to samples in frequency domain.
- real
Set frequency domain real expression for each separate channel separated by ’|’. Default is "re". If the number of input channels is greater than the number of expressions, the last specified expression is used for the remaining output channels.
- imag
Set frequency domain imaginary expression for each separate channel separated by ’|’. Default is "im".
Each expression in real and imag can contain the following constants and functions:
- sr
sample rate
- b
current frequency bin number
- nb
number of available bins
- ch
channel number of the current expression
- chs
number of channels
- pts
current frame pts
- re
current real part of frequency bin of current channel
- im
current imaginary part of frequency bin of current channel
- real(b, ch)
Return the value of real part of frequency bin at location (bin,channel)
- imag(b, ch)
Return the value of imaginary part of frequency bin at location (bin,channel)
- win_size
Set window size. Allowed range is from 16 to 131072. Default is
4096- win_func
Set window function.
It accepts the following values:
- ‘rect’
- ‘bartlett’
- ‘hann, hanning’
- ‘hamming’
- ‘blackman’
- ‘welch’
- ‘flattop’
- ‘bharris’
- ‘bnuttall’
- ‘bhann’
- ‘sine’
- ‘nuttall’
- ‘lanczos’
- ‘gauss’
- ‘tukey’
- ‘dolph’
- ‘cauchy’
- ‘parzen’
- ‘poisson’
- ‘bohman’
- ‘kaiser’
Default is
hann.- overlap
Set window overlap. If set to 1, the recommended overlap for selected window function will be picked. Default is
0.75.
Examples
- Leave almost only low frequencies in audio:
afftfilt="'real=re * (1-clip((b/nb)*b,0,1))':imag='im * (1-clip((b/nb)*b,0,1))'"
- Apply robotize effect:
afftfilt="real='hypot(re,im)*sin(0)':imag='hypot(re,im)*cos(0)':win_size=512:overlap=0.75"
- Apply whisper effect:
afftfilt="real='hypot(re,im)*cos((random(0)*2-1)*2*3.14)':imag='hypot(re,im)*sin((random(1)*2-1)*2*3.14)':win_size=128:overlap=0.8"
- Apply phase shift:
afftfilt="real=re*cos(1)-im*sin(1):imag=re*sin(1)+im*cos(1)"