Filter asettb
  Set timebase for the audio output link.
    Inputs:
       #0: default (audio)
    Outputs:
       #0: default (audio)
asettb AVOptions:
  expr              <string>     ..F.A.... set expression determining the output timebase (default "intb")
  tb                <string>     ..F.A.... set expression determining the output timebase (default "intb")


