Filter removegrain
  Remove grain.
    slice threading supported
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
removegrain AVOptions:
  m0                <int>        ..FV..... set mode for 1st plane (from 0 to 24) (default 0)
  m1                <int>        ..FV..... set mode for 2nd plane (from 0 to 24) (default 0)
  m2                <int>        ..FV..... set mode for 3rd plane (from 0 to 24) (default 0)
  m3                <int>        ..FV..... set mode for 4th plane (from 0 to 24) (default 0)

This filter has support for timeline through the 'enable' option.

