Filter showvolume
  Convert input audio volume to video output.
    Inputs:
       #0: default (audio)
    Outputs:
       #0: default (video)
showvolume AVOptions:
  rate              <video_rate> ..FV.... set video rate (default "25")
  r                 <video_rate> ..FV.... set video rate (default "25")
  b                 <int>        ..FV.... set border width (from 0 to 5) (default 1)
  w                 <int>        ..FV.... set channel width (from 80 to 8192) (default 400)
  h                 <int>        ..FV.... set channel height (from 1 to 900) (default 20)
  f                 <double>     ..FV.... set fade (from 0.001 to 1) (default 0.95)
  c                 <string>     ..FV.... set volume color expression (default "PEAK*255+floor((1-PEAK)*255)*256+0xff000000")
  t                 <boolean>    ..FV.... display channel names (default true)
  v                 <boolean>    ..FV.... display volume value (default true)
  o                 <int>        ..FV.... set orientation (from 0 to 1) (default h)
     h                            ..FV.... horizontal
     v                            ..FV.... vertical
  s                 <int>        ..FV.... set step size (from 0 to 5) (default 0)


