C:\cygwin64\bin>ffmpeg -re -i C:\\slack.mp4 -f rtp rtp://127.0.0.1:1234
ffmpeg version N-76419-gdee7440 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 5.2.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
  libavutil      55.  5.100 / 55.  5.100
  libavcodec     57. 13.102 / 57. 13.102
  libavformat    57. 13.100 / 57. 13.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 14.101 /  6. 14.101
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.100 /  2.  0.100
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\\slack.mp4':
  Metadata:
    major_brand     : qt
    minor_version   : 0
    compatible_brands: qt
    creation_time   : 2015-09-29 10:54:42
  Duration: 00:00:12.84, start: 0.000000, bitrate: 6954 kb/s
    Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 85 kb/s (default)
    Metadata:
      creation_time   : 2015-09-29 10:54:42
      handler_name    : Core Media Data Handler
    Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720, 6859 kb/s, 59.98 fps, 60 tbr, 600 tbn, 1200 tbc (default)
    Metadata:
      rotate          : 90
      creation_time   : 2015-09-29 10:54:42
      handler_name    : Core Media Data Handler
      encoder         : H.264
    Side data:
      displaymatrix: rotation of -90.00 degrees
[rtp @ 000000134c0b09a0] Only one stream supported in the RTP muxer
Output #0, rtp, to 'rtp://127.0.0.1:1234':
  Metadata:
    major_brand     : qt
    minor_version   : 0
    compatible_brands: qt
    encoder         : Lavf57.13.100
    Stream #0:0(und): Video: mpeg4, yuv420p, 720x1280, q=2-31, 200 kb/s, 60 fps, 60 tbn, 60 tbc (default)
    Metadata:
      handler_name    : Core Media Data Handler
      creation_time   : 2015-09-29 10:54:42
      encoder         : Lavc57.13.102 mpeg4
    Stream #0:1(und): Audio: pcm_mulaw, 44100 Hz, mono, s16, 352 kb/s (default)
    Metadata:
      creation_time   : 2015-09-29 10:54:42
      handler_name    : Core Media Data Handler
      encoder         : Lavc57.13.102 pcm_mulaw
Stream mapping:
  Stream #0:1 -> #0:0 (h264 (native) -> mpeg4 (native))
  Stream #0:0 -> #0:1 (aac (native) -> pcm_mulaw (native))
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument