Filter aevalsrc
  Generate an audio signal generated by an expression.
    Inputs:
        none (source filter)
    Outputs:
       #0: default (audio)
aevalsrc AVOptions:
  exprs             <string>     ..F.A.... set the '|'-separated list of channels expressions
  nb_samples        <int>        ..F.A.... set the number of samples per requested frame (from 0 to INT_MAX) (default 1024)
  n                 <int>        ..F.A.... set the number of samples per requested frame (from 0 to INT_MAX) (default 1024)
  sample_rate       <string>     ..F.A.... set the sample rate (default "44100")
  s                 <string>     ..F.A.... set the sample rate (default "44100")
  duration          <duration>   ..F.A.... set audio duration (default -0.000001)
  d                 <duration>   ..F.A.... set audio duration (default -0.000001)
  channel_layout    <string>     ..F.A.... set channel layout
  c                 <string>     ..F.A.... set channel layout


