Metadata Lost on Transcode to MP3

[br3wski3]

Transcode to MP3 loses metadata.

A simple transcode to mp3 shows metadata in the source and what is intended for the output. However, afterward, the generated file has none of the source file metadata.

Desktop>ffmpeg -i L:\br3wski3\WilliamGibson-NeuromancerD2.opus WilliamGibson-NeuromancerD2.mp3 -y
ffmpeg version N-80117-gdac030d Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmfx --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 43.100 / 57. 43.100
  libavformat    57. 37.101 / 57. 37.101
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 46.100 /  6. 46.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[ogg @ 033a8a40] 718 bytes of comment header remain
Input #0, ogg, from 'L:\br3wski3\WilliamGibson-NeuromancerD2.opus':
  Duration: 01:11:18.98, start: 0.000000, bitrate: 60 kb/s
    Stream #0:0: Audio: opus, 48000 Hz, stereo, fltp
    Metadata:
      ENCODER         : opusenc from opus-tools v0.1.9
      ARTIST          : William Gibson
      TITLE           : Neuromancer Disc 2
      ALBUM           : Neuromancer
      DATE            : 2011
      track           : 2
      TRACKTOTAL      : 9
      ALBUM ARTIST    : Robertson Dean
      GENRE           : Audiobook
      ENCODER_OPTIONS : --bitrate 64
    Stream #0:1: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 500x470 [SAR 96:96 DAR 50:47], 90k tbr, 90k tbn
    Metadata:
      comment         : Cover (front)
[swscaler @ 034ce020] deprecated pixel format used, make sure you did set range correctly
[mp3 @ 034c37e0] Frame rate very high for a muxer not efficiently supporting it.
Please consider specifying a lower framerate, a different muxer or -vsync 2
[mp3 @ 034c37e0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times
Output #0, mp3, to 'WilliamGibson-NeuromancerD2.mp3':
  Metadata:
    TSSE            : Lavf57.37.101
    Stream #0:0: Video: png, rgb24, 500x470 [SAR 1:1 DAR 50:47], q=2-31, 200 kb/s, 90k fps, 90k tbn
    Metadata:
      comment         : Cover (front)
      encoder         : Lavc57.43.100 png
    Stream #0:1: Audio: mp3, 48000 Hz, stereo, fltp
    Metadata:
      ENCODER_OPTIONS : --bitrate 64
      ARTIST          : William Gibson
      TITLE           : Neuromancer Disc 2
      ALBUM           : Neuromancer
      DATE            : 2011
      track           : 2
      TRACKTOTAL      : 9
      ALBUM ARTIST    : Robertson Dean
      GENRE           : Audiobook
      encoder         : Lavc57.43.100 libmp3lame
Stream mapping:
  Stream #0:1 -> #0:0 (mjpeg (native) -> png (native))
  Stream #0:0 -> #0:1 (opus (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=-0.0 Lsize=   67438kB time=01:11:18.97 bitrate= 129.1kbits/s speed=9.27x
video:578kB audio:66860kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000377%

Desktop>ffmpeg -i WilliamGibson-NeuromancerD2.mp3
ffmpeg version N-80117-gdac030d Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmfx --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 43.100 / 57. 43.100
  libavformat    57. 37.101 / 57. 37.101
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 46.100 /  6. 46.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mp3, from 'WilliamGibson-NeuromancerD2.mp3':
  Metadata:
    encoder         : Lavf57.37.101
  Duration: 01:11:19.01, start: 0.023021, bitrate: 129 kb/s
    Stream #0:0: Audio: mp3, 48000 Hz, stereo, s16p, 128 kb/s
    Metadata:
      encoder         : Lavc57.43
    Stream #0:1: Video: png, rgb24(pc), 500x470 [SAR 1:1 DAR 50:47], 90k tbr, 90k tbn
    Metadata:
      comment         : Cover (front)
At least one output file must be specified

[br3wski3]

Had revelation just after posting ticket that the metadata needed to be mapped from the opus audio stream to global for the output mp3 file.