Filter sr
  Apply DNN-based image super resolution to the input.
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
sr AVOptions:
  dnn_backend       <int>        ..FV....... DNN backend used for model execution (from 0 to 1) (default native)
     native          0            ..FV....... native backend flag
  scale_factor      <int>        ..FV....... scale factor for SRCNN model (from 2 to 4) (default 2)
  model             <string>     ..FV....... path to model file specifying network architecture and its parameters


