title: ffmpeg PNG - MP4 - Error opening input files: invalid argument
body: <p>I am following along with this
  <a href="http://markov.uc3m.es/2012/11/temporal-networks-with-igraph-and-r-with-20-lines-of-code" rel="nofollow">visualization project</a>
  converting PNG files in an MP4.</p>
  
  <p>The only change from the code on the example is that my time stamp starts with
  1.</p>
  
  <pre>
  ffmpeg -r 20 -b 20M -i example%01d.png output.mp4
  </pre>
  
  <p>And this is what returns</p>
  
  <pre>
  ffmpeg version N-53055-g7b43120 Copyright (c) 2000-2013 the FFmpeg developers
  built on May 14 2013 20:43:53 with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  configuration: --disable-yasm
  libavutil      52. 31.100 / 52. 31.100
  libavcodec     55.  9.100 / 55.  9.100
  libavformat    55.  7.100 / 55.  7.100
  libavdevice    55.  0.100 / 55.  0.100
  libavfilter     3. 67.100 /  3. 67.100
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  **Option b (video bitrate (please use -b:v)) cannot be applied to input file
  example%01d.png -- you are trying to apply an input option to an output file or
  vice versa. Move this option before the file it belongs to.
  Error parsing options for input file example%01d.png.
  Error opening input files: Invalid argument**
  </pre>