FFMPEG:ffmpeg version 3.3.3 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.1.1 (GCC) 20170630
  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-libschroedinger --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. 58.100 / 55. 58.100
  libavcodec     57. 89.100 / 57. 89.100

FFMPEG:  libavformat    57. 71.100 / 57. 71.100
  libavdevice    57.  6.100 / 57.  6.100
  libavfilter     6. 82.100 /  6. 82.100
  libavresample   3.  5.  0 /  3.  5.  0
  libswscale      4.  6.100 /  4.  6.100
  libswresample   2.  7.100 /  2.  7.100
  libpostproc    54.  5.100 / 54.  5.100

FFMPEG:[libvpx @ 0x5623a5321b60] v1.6.1

FFMPEG:Input #0, matroska,webm, from 'pipe:':
  Metadata:
    encoder         : QTmuxingAppLibWebM-0.0.1

FFMPEG:  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0(eng): Video: vp8, yuv420p(tv, progressive), 320x240, SAR 1:1 DAR 4:3, 1k tbr, 1k tbn, 1k tbc (default)
    Stream #0:1(eng): Audio: opus, 48000 Hz, stereo, fltp (default)

FFMPEG:[libvpx @ 0x5623a5461a20] v1.6.1

FFMPEG:[flv @ 0x5623a54a3c00] Video codec vp8 not compatible with flv
Could not write header for output file #1 (incorrect codec parameters ?): Function not implemented
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (libvpx) -> h264 (libx264))
  Stream #0:1 -> #0:1 (opus (native) -> mp3 (libmp3lame))
  Stream #0:0 -> #1:0 (copy)
  Stream #0:1 -> #1:1 (copy)
    Last message repeated 1 times

ERROR: unexpected:ffmpeg exit!1