Filter compand
  Compress or expand audio dynamic range.
    Inputs:
       #0: default (audio)
    Outputs:
       #0: default (audio)
compand AVOptions:
  attacks           <string>     ..F.A.... set time over which increase of volume is determined (default "0")
  decays            <string>     ..F.A.... set time over which decrease of volume is determined (default "0.8")
  points            <string>     ..F.A.... set points of transfer function (default "-70/-70|-60/-20|1/0")
  soft-knee         <double>     ..F.A.... set soft-knee (from 0.01 to 900) (default 0.01)
  gain              <double>     ..F.A.... set output gain (from -900 to 900) (default 0)
  volume            <double>     ..F.A.... set initial volume (from -900 to 0) (default 0)
  delay             <double>     ..F.A.... set delay for samples before sending them to volume adjuster (from 0 to 20) (default 0)


