Filter sine
  Generate sine wave audio signal.
    Inputs:
        none (source filter)
    Outputs:
       #0: default (audio)
sine AVOptions:
  frequency         <double>     ..F.A.... set the sine frequency (from 0 to DBL_MAX) (default 440)
  f                 <double>     ..F.A.... set the sine frequency (from 0 to DBL_MAX) (default 440)
  beep_factor       <double>     ..F.A.... set the beep frequency factor (from 0 to DBL_MAX) (default 0)
  b                 <double>     ..F.A.... set the beep frequency factor (from 0 to DBL_MAX) (default 0)
  sample_rate       <int>        ..F.A.... set the sample rate (from 1 to INT_MAX) (default 44100)
  r                 <int>        ..F.A.... set the sample rate (from 1 to INT_MAX) (default 44100)
  duration          <duration>   ..F.A.... set the audio duration (default 0)
  d                 <duration>   ..F.A.... set the audio duration (default 0)
  samples_per_frame <string>     ..F.A.... set the number of samples per frame (default "1024")


