Filter headphone
  Apply headphone binaural spatialization with HRTFs in additional streams.
    slice threading supported
    Inputs:
        dynamic (depending on the options)
    Outputs:
       #0: default (audio)
headphone AVOptions:
  map               <string>     ..F.A... set channels convolution mappings
  gain              <float>      ..F.A... set gain in dB (from -20 to 40) (default 0)
  lfe               <float>      ..F.A... set lfe gain in dB (from -20 to 40) (default 0)
  type              <int>        ..F.A... set processing (from 0 to 1) (default freq)
     time                         ..F.A... time domain
     freq                         ..F.A... frequency domain


