Input #0, lavfi, from 'sine=r=32000':
  Duration: N/A, start: 0.000000, bitrate: 512 kb/s
    Stream #0:0: Audio: pcm_s16le, 32000 Hz, mono, s16, 512 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> opus (libopus))
Press [q] to stop, [?] for help
[libopus @ 0000013d45e64e40] No bit rate set. Defaulting to 64000 bps.
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Audio: opus (libopus), 24000 Hz, mono, s16, 64 kb/s
    Metadata:
      encoder         : Lavc58.35.100 libopus