ffmpeg -f avfoundation -i "0:0" out.mpg # .avi yields the same results
ffmpeg version 2.7.2 Copyright (c) 2000-2015 the FFmpeg developers
  built with Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.7.2_1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda
  libavutil      54. 27.100 / 54. 27.100
  libavcodec     56. 41.100 / 56. 41.100
  libavformat    56. 36.100 / 56. 36.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 16.101 /  5. 16.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.100 /  1.  2.100
  libpostproc    53.  3.100 / 53.  3.100
[avfoundation @ 0x7ffc2380da00] Selected framerate (29.970030) is not supported by the device
[avfoundation @ 0x7ffc2380da00] Supported modes:
[avfoundation @ 0x7ffc2380da00]   1280x720@[1.000000 30.000000]fps
    Last message repeated 2 times
[avfoundation @ 0x7ffc2380da00]   640x480@[1.000000 30.000000]fps
    Last message repeated 2 times
[avfoundation @ 0x7ffc2380da00]   320x240@[1.000000 30.000000]fps
    Last message repeated 2 times
0:0: Input/output error