Filter aiir
  Apply Infinite Impulse Response filter with supplied coefficients.
    slice threading supported
    Inputs:
       #0: default (audio)
    Outputs:
        dynamic (depending on the options)
aiir AVOptions:
  z                 <string>     ..F.A.... set B/numerator/zeros coefficients (default "1+0i 1-0i")
  p                 <string>     ..F.A.... set A/denominator/poles coefficients (default "1+0i 1-0i")
  k                 <string>     ..F.A.... set channels gains (default "1|1")
  dry               <double>     ..F.A.... set dry gain (from 0 to 1) (default 1)
  wet               <double>     ..F.A.... set wet gain (from 0 to 1) (default 1)
  f                 <int>        ..F.A.... set coefficients format (from 0 to 3) (default zp)
     tf              0            ..F.A.... transfer function
     zp              1            ..F.A.... Z-plane zeros/poles
     pr              2            ..F.A.... Z-plane zeros/poles (polar radians)
     pd              3            ..F.A.... Z-plane zeros/poles (polar degrees)
  r                 <int>        ..F.A.... set kind of processing (from 0 to 1) (default s)
     d               0            ..F.A.... direct
     s               1            ..F.A.... serial cascading
  e                 <int>        ..F.A.... set precision (from 0 to 3) (default dbl)
     dbl             0            ..F.A.... double-precision floating-point
     flt             1            ..F.A.... single-precision floating-point
     i32             2            ..F.A.... 32-bit integers
     i16             3            ..F.A.... 16-bit integers
  mix               <double>     ..F.A.... set mix (from 0 to 1) (default 1)
  response          <boolean>    ..FV..... show IR frequency response (default false)
  channel           <int>        ..FV..... set IR channel to display frequency response (from 0 to 1024) (default 0)
  size              <image_size> ..FV..... set video size (default "hd720")
  rate              <video_rate> ..FV..... set video rate (default "25")


