$ ffmpeg  -i Good.webm
ffmpeg version 2.4.3 Copyright (c) 2000-2014 the FFmpeg developers
  built on Nov 20 2014 15:50:25 with Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.4.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid --enable-libfreetype --enable-libvorbis --enable-libvpx --enable-libass --enable-ffplay --enable-libfdk-aac --enable-libopus --enable-libquvi --enable-libx265 --enable-vda
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  1.100 / 56.  1.100
  libavformat    56.  4.101 / 56.  4.101
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  1.100 /  5.  1.100
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
Input #0, matroska,webm, from 'UserInterview_EHGLIXR8UBA_ET2GYGBFW4.webm':
  Metadata:
    encoder         : Lavf55.19.104
  Duration: 00:00:11.11, start: 0.000000, bitrate: 107 kb/s
    Stream #0:0: Video: vp8, yuv420p, 320x240, SAR 1:1 DAR 4:3, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: vorbis, 8000 Hz, mono, fltp
At least one output file must be specified
$ ffmpeg  -i Bad.webm
ffmpeg version 2.4.3 Copyright (c) 2000-2014 the FFmpeg developers
  built on Nov 20 2014 15:50:25 with Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.4.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid --enable-libfreetype --enable-libvorbis --enable-libvpx --enable-libass --enable-ffplay --enable-libfdk-aac --enable-libopus --enable-libquvi --enable-libx265 --enable-vda
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  1.100 / 56.  1.100
  libavformat    56.  4.101 / 56.  4.101
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  1.100 /  5.  1.100
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
Input #0, matroska,webm, from 'RN8N5WT37RO.webm':
  Metadata:
    encoder         : Lavf56.4.101
  Duration: 00:00:11.12, start: 0.000000, bitrate: 116 kb/s
    Stream #0:0: Video: vp8, yuv420p, 320x240, SAR 1:1 DAR 4:3, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: vorbis, 8000 Hz, mono, fltp (default)
At least one output file must be specified