Muxer ast [AST (Audio Stream)]:
    Common extensions: ast.
    Default audio codec: pcm_s16be_planar.
AST muxer AVOptions:
  -loopstart         <int64>      E..... Loopstart position in milliseconds. (from -1 to INT_MAX)
  -loopend           <int64>      E..... Loopend position in milliseconds. (from 0 to INT_MAX)

