$ ffmpeg -re -i big_buck_bunny_480p_h264.mov -map 0:0 -flush_packets 1 -vf scale=640x480 -f v4l2 /dev/video0
ffmpeg version 3.4.4-0ubuntu0.18.04.1 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  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
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'big_buck_bunny_480p_h264.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2008-05-27T18:32:32.000000Z
    com.apple.quicktime.player.movie.audio.gain: 1.000000
    com.apple.quicktime.player.movie.audio.treble: 0.000000
    com.apple.quicktime.player.movie.audio.bass: 0.000000
    com.apple.quicktime.player.movie.audio.balance: 0.000000
    com.apple.quicktime.player.movie.audio.pitchshift: 0.000000
    com.apple.quicktime.player.movie.audio.mute:
    com.apple.quicktime.player.movie.visual.brightness: 0.000000
    com.apple.quicktime.player.movie.visual.color: 1.000000
    com.apple.quicktime.player.movie.visual.tint: 0.000000
    com.apple.quicktime.player.movie.visual.contrast: 1.000000
    com.apple.quicktime.player.version: 7.4.1 (14)
    com.apple.quicktime.version: 7.4.1 (14) 0x7418000 (Mac OS X, 10.5.2, 9C31)
    timecode        : 00:00:00:00
  Duration: 00:09:56.46, start: 0.000000, bitrate: 3342 kb/s
    Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 853x480, 2899 kb/s, 24 fps, 24 tbr, 2400 tbn, 4800 tbc (default)
    Metadata:
      rotate          : 0
      creation_time   : 2008-05-27T18:32:32.000000Z
      handler_name    : Apple Alias Data Handler
      encoder         : H.264
    Side data:
      displaymatrix: rotation of -0.00 degrees
    Stream #0:1(eng): Data: none (tmcd / 0x64636D74) (default)
    Metadata:
      rotate          : 0
      creation_time   : 2008-05-27T18:32:32.000000Z
      handler_name    : Apple Alias Data Handler
      timecode        : 00:00:00:00
    Stream #0:2(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 437 kb/s (default)
    Metadata:
      rotate          : 0
      creation_time   : 2008-05-27T18:32:32.000000Z
      handler_name    : Apple Alias Data Handler
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, v4l2, to '/dev/video0': time=-577014:32:22.77 bitrate=N/A speed=N/A
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    timecode        : 00:00:00:00
    com.apple.quicktime.player.movie.audio.gain: 1.000000
    com.apple.quicktime.player.movie.audio.treble: 0.000000
    com.apple.quicktime.player.movie.audio.bass: 0.000000
    com.apple.quicktime.player.movie.audio.balance: 0.000000
    com.apple.quicktime.player.movie.audio.pitchshift: 0.000000
    com.apple.quicktime.player.movie.audio.mute:
    com.apple.quicktime.player.movie.visual.brightness: 0.000000
    com.apple.quicktime.player.movie.visual.color: 1.000000
    com.apple.quicktime.player.movie.visual.tint: 0.000000
    com.apple.quicktime.player.movie.visual.contrast: 1.000000
    com.apple.quicktime.player.version: 7.4.1 (14)
    com.apple.quicktime.version: 7.4.1 (14) 0x7418000 (Mac OS X, 10.5.2, 9C31)
    encoder         : Lavf57.83.100
    Stream #0:0(eng): Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480, q=2-31, 88473 kb/s, 24 fps, 24 tbn, 24 tbc (default)
    Metadata:
      encoder         : Lavc57.107.100 rawvideo
      creation_time   : 2008-05-27T18:32:32.000000Z
      handler_name    : Apple Alias Data Handler
    Side data:
      displaymatrix: rotation of -0.00 degrees