ffmpeg version N-94156-g93a73df54d Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190621
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enab
le-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpac
k --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --e
nable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 30.100 / 56. 30.100
  libavcodec     58. 53.101 / 58. 53.101
  libavformat    58. 28.101 / 58. 28.101
  libavdevice    58.  7.100 / 58.  7.100
  libavfilter     7. 56.100 /  7. 56.100
  libswscale      5.  4.101 /  5.  4.101
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
Input #0, concat, from 'mylist.txt':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0(eng): Audio: opus, 48000 Hz, mono, fltp
    Stream #0:1(eng): Video: vp9 (Profile 0), yuv420p(tv), 1920x1080, SAR 1:1 DAR 16:9, 16.67 fps, 16.67 tbr, 1k tbn, 1k tbc
    Metadata:
      alpha_mode      : 1
File 'undivided.webm' already exists. Overwrite ? [y/N] y
Output #0, webm, to 'undivided.webm':
  Metadata:
    encoder         : Lavf58.28.101
    Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 16.67 fps, 16.67 tbr, 1k tbn, 1k tbc
    Metadata:
      alpha_mode      : 1
    Stream #0:1(eng): Audio: opus, 48000 Hz, mono, fltp
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
  Stream #0:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=  496 fps=0.0 q=-1.0 Lsize=   12628kB time=00:00:28.42 bitrate=3639.1kbits/s speed=30.7x
video:12508kB audio:113kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.057648%