ffmpeg -i "$INMOV" -c copy -ss 0:09 -to 0:13 out.webm
ffmpeg version 3.2.2 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 6.2.1 (GCC) 20160830
  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-libxvid --enable-netcdf --enable-shared --enable-version3 --enable-x11grab
  libavutil      55. 34.100 / 55. 34.100
  libavcodec     57. 64.101 / 57. 64.101
  libavformat    57. 56.100 / 57. 56.100
  libavdevice    57.  1.100 / 57.  1.100
  libavfilter     6. 65.100 /  6. 65.100
  libavresample   3.  1.  0 /  3.  1.  0
  libswscale      4.  2.100 /  4.  2.100
  libswresample   2.  3.100 /  2.  3.100
  libpostproc    54.  1.100 / 54.  1.100
Input #0, matroska,webm, from 'Generational Curse 1 - Nigerian Movies 2016 Latest Full Movies _ African Movies _ English Full _Epic-kud8e1PKxDA.mkv':
  Metadata:
    COMPATIBLE_BRANDS: iso6avc1mp41
    MAJOR_BRAND     : dash
    MINOR_VERSION   : 0
    ENCODER         : Lavf57.56.100
  Duration: 01:41:54.34, start: -0.007000, bitrate: 902 kb/s
    Stream #0:0: Video: h264 (Main), yuv420p(progressive), 852x480 [SAR 1:1 DAR 71:40], 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
    Metadata:
      HANDLER_NAME    : VideoHandler
      DURATION        : 01:41:54.280000000
    Stream #0:1(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      DURATION        : 01:41:54.341000000
Output #0, webm, to 'out.webm':
  Metadata:
    COMPATIBLE_BRANDS: iso6avc1mp41
    MAJOR_BRAND     : dash
    MINOR_VERSION   : 0
    encoder         : Lavf57.56.100
    Stream #0:0: Video: h264 (Main), yuv420p(progressive), 852x480 [SAR 1:1 DAR 71:40], q=2-31, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      HANDLER_NAME    : VideoHandler
      DURATION        : 01:41:54.280000000
    Stream #0:1(eng): Audio: opus, 48000 Hz, stereo (default)
    Metadata:
      DURATION        : 01:41:54.341000000
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
[webm @ 0x55ff5be124c0] Only VP8 or VP9 video and Vorbis or Opus audio and WebVTT subtitles are supported for WebM.
av_interleaved_write_frame(): Invalid argument
Error writing trailer of out.webm: Invalid argumentframe=    1 fps=0.0 q=-1.0 Lsize=       0kB time=00:00:01.20 bitrate=   2.4kbits/s speed= 153x    
video:32kB audio:27kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Conversion failed!