Filter addroi
  Add region of interest to frame.
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
addroi AVOptions:
  x                 <string>     ..FV..... Region distance from left edge of frame. (default "0")
  y                 <string>     ..FV..... Region distance from top edge of frame. (default "0")
  w                 <string>     ..FV..... Region width. (default "0")
  h                 <string>     ..FV..... Region height. (default "0")
  qoffset           <rational>   ..FV..... Quantisation offset to apply in the region. (from -1 to 1) (default -1/10)
  clear             <boolean>    ..FV..... Remove any existing regions of interest before adding the new one. (default false)


