Filter biquad
  Apply a biquad IIR filter with the given coefficients.
    slice threading supported
    Inputs:
       #0: default (audio)
    Outputs:
       #0: default (audio)
biquad AVOptions:
  a0                <double>     ..F.A....T. (from INT_MIN to INT_MAX) (default 1)
  a1                <double>     ..F.A....T. (from INT_MIN to INT_MAX) (default 0)
  a2                <double>     ..F.A....T. (from INT_MIN to INT_MAX) (default 0)
  b0                <double>     ..F.A....T. (from INT_MIN to INT_MAX) (default 0)
  b1                <double>     ..F.A....T. (from INT_MIN to INT_MAX) (default 0)
  b2                <double>     ..F.A....T. (from INT_MIN to INT_MAX) (default 0)
  mix               <double>     ..F.A....T. set mix (from 0 to 1) (default 1)
  m                 <double>     ..F.A....T. set mix (from 0 to 1) (default 1)
  channels          <channel_layout> ..F.A....T. set channels to filter (default 0xffffffffffffffff)
  c                 <channel_layout> ..F.A....T. set channels to filter (default 0xffffffffffffffff)
  normalize         <boolean>    ..F.A....T. normalize coefficients (default false)
  n                 <boolean>    ..F.A....T. normalize coefficients (default false)
  transform         <int>        ..F.A...... set transform type (from 0 to 3) (default di)
     di              0            ..F.A...... direct form I
     dii             1            ..F.A...... direct form II
     tdii            2            ..F.A...... transposed direct form II
     latt            3            ..F.A...... lattice-ladder form
  a                 <int>        ..F.A...... set transform type (from 0 to 3) (default di)
     di              0            ..F.A...... direct form I
     dii             1            ..F.A...... direct form II
     tdii            2            ..F.A...... transposed direct form II
     latt            3            ..F.A...... lattice-ladder form
  precision         <int>        ..F.A...... set filtering precision (from -1 to 3) (default auto)
     auto            -1           ..F.A...... automatic
     s16             0            ..F.A...... signed 16-bit
     s32             1            ..F.A...... signed 32-bit
     f32             2            ..F.A...... floating-point single
     f64             3            ..F.A...... floating-point double
  r                 <int>        ..F.A...... set filtering precision (from -1 to 3) (default auto)
     auto            -1           ..F.A...... automatic
     s16             0            ..F.A...... signed 16-bit
     s32             1            ..F.A...... signed 32-bit
     f32             2            ..F.A...... floating-point single
     f64             3            ..F.A...... floating-point double

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

