patrick@patrick-VirtualBox:~/Arbeitsfläche/hiwi$ ffmpeg -start_number 5  -i gopr0043.mp4 %06d.png
ffmpeg version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
  built on Jun 12 2012 16:37:58 with gcc 4.6.3
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
Unrecognized option 'start_number'
Failed to set value '5' for option 'start_number'

patrick@patrick-VirtualBox:~/Arbeitsfläche/hiwi$ avconv -start_number 5  -i gopr0043.mp4 %06d.png
avconv version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
  built on Jun 12 2012 16:37:58 with gcc 4.6.3
Unrecognized option 'start_number'
Failed to set value '5' for option 'start_number'