Apply boxblur algorithm to the input video.

This filter accepts the parameters: luma_radius:luma_power:chroma_radius:chroma_power:alpha_radius:alpha_power

Chroma and alpha parameters are optional, if not specified they default to the corresponding values set for luma_radius and luma_power.

luma_radius, chroma_radius, and alpha_radius represent the radius in pixels of the box used for blurring the corresponding input plane. They are expressions, and can contain the following constants:

w, h

the input width and height in pixels

cw, ch

the input chroma image width and height in pixels

hsub, vsub

horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

The radius must be a non-negative number, and must not be greater than the value of the expression min(w,h)/2 for the luma and alpha planes, and of min(cw,ch)/2 for the chroma planes.

luma_power, chroma_power, and alpha_power represent how many times the boxblur filter is applied to the corresponding plane.

Some examples follow:

• Apply a boxblur filter with luma, chroma, and alpha radius set to 2:

  boxblur=2:1

• Set luma radius to 2, alpha and chroma radius to 0

  boxblur=2:1:0:0:0:0

• Set luma and chroma radius to a fraction of the video dimension

  boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1