Filter buffer
  Buffer video frames, and make them accessible to the filterchain.
    Inputs:
        none (source filter)
    Outputs:
       #0: default (video)
buffer AVOptions:
  width             <int>        ..FV....... (from 0 to INT_MAX) (default 0)
  video_size        <image_size> ..FV.......
  height            <int>        ..FV....... (from 0 to INT_MAX) (default 0)
  pix_fmt           <pix_fmt>    ..FV....... (default none)
  sar               <rational>   ..FV....... sample aspect ratio (from 0 to DBL_MAX) (default 0/1)
  pixel_aspect      <rational>   ..FV....... sample aspect ratio (from 0 to DBL_MAX) (default 0/1)
  time_base         <rational>   ..FV....... (from 0 to DBL_MAX) (default 0/1)
  frame_rate        <rational>   ..FV....... (from 0 to DBL_MAX) (default 0/1)
  sws_param         <string>     ..FV.......


