Filter surround
  Apply audio surround upmix filter.
    slice threading supported
    Inputs:
       #0: default (audio)
    Outputs:
       #0: default (audio)
surround AVOptions:
  chl_out           <string>     ..F.A.... set output channel layout (default "5.1")
  chl_in            <string>     ..F.A.... set input channel layout (default "stereo")
  level_in          <float>      ..F.A.... set input level (from 0 to 10) (default 1)
  level_out         <float>      ..F.A.... set output level (from 0 to 10) (default 1)
  lfe               <boolean>    ..F.A.... output LFE (default true)
  lfe_low           <int>        ..F.A.... LFE low cut off (from 0 to 256) (default 128)
  lfe_high          <int>        ..F.A.... LFE high cut off (from 0 to 512) (default 256)
  lfe_mode          <int>        ..F.A.... set LFE channel mode (from 0 to 1) (default add)
     add             0            ..F.A.... just add LFE channel
     sub             1            ..F.A.... substract LFE channel with others
  angle             <float>      ..F.A.... set soundfield transform angle (from 0 to 360) (default 90)
  fc_in             <float>      ..F.A.... set front center channel input level (from 0 to 10) (default 1)
  fc_out            <float>      ..F.A.... set front center channel output level (from 0 to 10) (default 1)
  fl_in             <float>      ..F.A.... set front left channel input level (from 0 to 10) (default 1)
  fl_out            <float>      ..F.A.... set front left channel output level (from 0 to 10) (default 1)
  fr_in             <float>      ..F.A.... set front right channel input level (from 0 to 10) (default 1)
  fr_out            <float>      ..F.A.... set front right channel output level (from 0 to 10) (default 1)
  sl_in             <float>      ..F.A.... set side left channel input level (from 0 to 10) (default 1)
  sl_out            <float>      ..F.A.... set side left channel output level (from 0 to 10) (default 1)
  sr_in             <float>      ..F.A.... set side right channel input level (from 0 to 10) (default 1)
  sr_out            <float>      ..F.A.... set side right channel output level (from 0 to 10) (default 1)
  bl_in             <float>      ..F.A.... set back left channel input level (from 0 to 10) (default 1)
  bl_out            <float>      ..F.A.... set back left channel output level (from 0 to 10) (default 1)
  br_in             <float>      ..F.A.... set back right channel input level (from 0 to 10) (default 1)
  br_out            <float>      ..F.A.... set back right channel output level (from 0 to 10) (default 1)
  bc_in             <float>      ..F.A.... set back center channel input level (from 0 to 10) (default 1)
  bc_out            <float>      ..F.A.... set back center channel output level (from 0 to 10) (default 1)
  lfe_in            <float>      ..F.A.... set lfe channel input level (from 0 to 10) (default 1)
  lfe_out           <float>      ..F.A.... set lfe channel output level (from 0 to 10) (default 1)
  allx              <float>      ..F.A.... set all channel's x spread (from -1 to 15) (default -1)
  ally              <float>      ..F.A.... set all channel's y spread (from -1 to 15) (default -1)
  fcx               <float>      ..F.A.... set front center channel x spread (from 0 to 15) (default 1)
  flx               <float>      ..F.A.... set front left channel x spread (from 0 to 15) (default 1)
  frx               <float>      ..F.A.... set front right channel x spread (from 0 to 15) (default 1)
  blx               <float>      ..F.A.... set back left channel x spread (from 0 to 15) (default 1)
  brx               <float>      ..F.A.... set back right channel x spread (from 0 to 15) (default 1)
  slx               <float>      ..F.A.... set side left channel x spread (from 0 to 15) (default 1)
  srx               <float>      ..F.A.... set side right channel x spread (from 0 to 15) (default 1)
  bcx               <float>      ..F.A.... set back center channel x spread (from 0 to 15) (default 1)
  fcy               <float>      ..F.A.... set front center channel y spread (from 0 to 15) (default 1)
  fly               <float>      ..F.A.... set front left channel y spread (from 0 to 15) (default 1)
  fry               <float>      ..F.A.... set front right channel y spread (from 0 to 15) (default 1)
  bly               <float>      ..F.A.... set back left channel y spread (from 0 to 15) (default 1)
  bry               <float>      ..F.A.... set back right channel y spread (from 0 to 15) (default 1)
  sly               <float>      ..F.A.... set side left channel y spread (from 0 to 15) (default 1)
  sry               <float>      ..F.A.... set side right channel y spread (from 0 to 15) (default 1)
  bcy               <float>      ..F.A.... set back center channel y spread (from 0 to 15) (default 1)
  win_size          <int>        ..F.A.... set window size (from 1024 to 65536) (default 4096)
  win_func          <int>        ..F.A.... set window function (from 0 to 19) (default hann)
     rect            0            ..F.A.... Rectangular
     bartlett        4            ..F.A.... Bartlett
     hann            1            ..F.A.... Hann
     hanning         1            ..F.A.... Hanning
     hamming         2            ..F.A.... Hamming
     blackman        3            ..F.A.... Blackman
     welch           5            ..F.A.... Welch
     flattop         6            ..F.A.... Flat-top
     bharris         7            ..F.A.... Blackman-Harris
     bnuttall        8            ..F.A.... Blackman-Nuttall
     bhann           11           ..F.A.... Bartlett-Hann
     sine            9            ..F.A.... Sine
     nuttall         10           ..F.A.... Nuttall
     lanczos         12           ..F.A.... Lanczos
     gauss           13           ..F.A.... Gauss
     tukey           14           ..F.A.... Tukey
     dolph           15           ..F.A.... Dolph-Chebyshev
     cauchy          16           ..F.A.... Cauchy
     parzen          17           ..F.A.... Parzen
     poisson         18           ..F.A.... Poisson
     bohman          19           ..F.A.... Bohman
  overlap           <float>      ..F.A.... set window overlap (from 0 to 1) (default 0.5)


