fftfilt

Apply arbitrary expressions to samples in frequency domain

dc_Y

Adjust the dc value (gain) of the luma plane of the image. The filter accepts an integer value in range 0 to 1000. The default value is set to 0.

dc_U

Adjust the dc value (gain) of the 1st chroma plane of the image. The filter accepts an integer value in range 0 to 1000. The default value is set to 0.

dc_V

Adjust the dc value (gain) of the 2nd chroma plane of the image. The filter accepts an integer value in range 0 to 1000. The default value is set to 0.

weight_Y

Set the frequency domain weight expression for the luma plane.

weight_U

Set the frequency domain weight expression for the 1st chroma plane.

weight_V

Set the frequency domain weight expression for the 2nd chroma plane.

eval

Set when the expressions are evaluated.

It accepts the following values:

‘init’

Only evaluate expressions once during the filter initialization.

‘frame’

Evaluate expressions for each incoming frame.

Default value is ‘init’.

The filter accepts the following variables:

X

Y

The coordinates of the current sample.

W

H

The width and height of the image.

N

The number of input frame, starting from 0.

WS

HS

The size of FFT array for horizontal and vertical processing.

Examples

• High-pass:

  fftfilt=dc_Y=128:weight_Y='squish(1-(Y+X)/100)'
  

• Low-pass:

  fftfilt=dc_Y=0:weight_Y='squish((Y+X)/100-1)'
  

• Sharpen:

  fftfilt=dc_Y=0:weight_Y='1+squish(1-(Y+X)/100)'
  

• Blur:

  fftfilt=dc_Y=0:weight_Y='exp(-4 * ((Y+X)/(W+H)))'