E:\>ffmpeg.exe -i rawaudio.wav audio.opus
ffmpeg version N-82597-gd316b21 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx
--enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls
--enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfree
type --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enab
le-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspe
ex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvo
rbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable
-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 40.100 / 55. 40.100
  libavcodec     57. 66.106 / 57. 66.106
  libavformat    57. 58.100 / 57. 58.100
  libavdevice    57.  2.100 / 57.  2.100
  libavfilter     6. 67.100 /  6. 67.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100
Input #0, wav, from 'rawaudio.wav':
  Metadata:
    encoder         : Lavf57.58.100
  Duration: 00:57:37.77, bitrate: 6912 kb/s
    Stream #0:0: Audio: pcm_s24le ([1][0][0][0] / 0x0001), 48000 Hz, 5.1, s32 (24 bit), 6912 kb/s
[libopus @ 03a82080] No bit rate set. Defaulting to 320000 bps.
Output #0, opus, to 'audio.opus':
  Metadata:
    encoder         : Lavf57.58.100
    Stream #0:0: Audio: opus (libopus), 48000 Hz, 5.1, flt (24 bit), 320 kb/s
    Metadata:
      encoder         : Lavc57.66.106 libopus
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s24le (native) -> opus (libopus))
Press [q] to stop, [?] for help
size=  141830kB time=00:57:37.77 bitrate= 336.0kbits/s speed=24.9x
video:0kB audio:141099kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.518001%