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            0            ..F.A.... time domain
     freq            1            ..F.A.... frequency domain
  size              <int>        ..F.A.... set frame size (from 1024 to 96000) (default 1024)
  hrir              <int>        ..F.A.... set hrir format (from 0 to 1) (default stereo)
     stereo          0            ..F.A.... hrir files have exactly 2 channels
     multich         1            ..F.A.... single multichannel hrir file


