Unable to enable FEC on libopus

[Simon Blandford]

Summary of the bug:
-fec switch does not work as expected on libopus.

According to the docs, libopus requires the fec option to enable forward error correction.

https://ffmpeg.org/ffmpeg-codecs.html#libopus-1

However the error, "Unsupported FEC protocol" is output regardless of what I try to set it to.

How to reproduce:

% ffmpeg -re -f lavfi -i sine=frequency=864 -c:a libopus -fec 1 -packet_loss 10 -ac 1 -b:a 32k -ar 48000 -f rtp rtp://0.0.0.0:5020
ffmpeg version N-109079-g3ab11dc5bb-https://www.martin-riedl.de Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 10 (Debian 10.2.1-6)
  configuration: --prefix=/home/ffmpegBuild/out --enable-gpl --pkg-config-flags=--static --extra-version='https://www.martin-riedl.de' --enable-gray --enable-libxml2 --enable-libfreetype --enable-fontconfig --enable-libbluray --enable-libass --enable-libzvbi --enable-libaom --enable-libopenh264 --enable-librav1e --enable-libsvtav1 --enable-libvpx --enable-libx264 --enable-libx265 --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libtheora
  libavutil      57. 42.100 / 57. 42.100
  libavcodec     59. 52.102 / 59. 52.102
  libavformat    59. 34.101 / 59. 34.101
  libavdevice    59.  8.101 / 59.  8.101
  libavfilter     8. 50.100 /  8. 50.100
  libswscale      6.  8.112 /  6.  8.112
  libswresample   4.  9.100 /  4.  9.100
  libpostproc    56.  7.100 / 56.  7.100
Input #0, lavfi, from 'sine=frequency=864':
  Duration: N/A, start: 0.000000, bitrate: 705 kb/s
  Stream #0:0: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s
[rtp @ 0x559aab9580c0] Unsupported FEC protocol 1
rtp://0.0.0.0:5020: Input/output error