ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.2.1 (GCC) 20171128
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxvid --enable-shared --enable-version3
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
[aac @ 0x5631584c4a00] Estimating duration from bitrate, this may be inaccurate
Input #0, aac, from 'silent-audio.aac':
  Duration: 00:00:06.00, bitrate: 95 kb/s
    Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp, 95 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (aac (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, null, to '/dev/null':
  Metadata:
    encoder         : Lavf57.83.100
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
    Metadata:
      encoder         : Lavc57.107.100 pcm_s16le
Invalid return value 0 for stream protocol
size=N/A time=00:00:05.99 bitrate=N/A speed= 962x    
video:0kB audio:1032kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
[Parsed_volumedetect_0 @ 0x5631584cafa0] n_samples: 528384
[Parsed_volumedetect_0 @ 0x5631584cafa0] mean_volume: -84.3 dB
[Parsed_volumedetect_0 @ 0x5631584cafa0] max_volume: -84.3 dB
[Parsed_volumedetect_0 @ 0x5631584cafa0] histogram_84db: 526686