Filter aselect
  Select audio frames to pass in output.
    Inputs:
       #0: default (audio)
    Outputs:
        dynamic (depending on the options)
aselect AVOptions:
  expr              <string>     ..F.A.... set an expression to use for selecting frames (default "1")
  e                 <string>     ..F.A.... set an expression to use for selecting frames (default "1")
  outputs           <int>        ..F.A.... set the number of outputs (from 1 to INT_MAX) (default 1)
  n                 <int>        ..F.A.... set the number of outputs (from 1 to INT_MAX) (default 1)


