Comment 11 for bug 730159

The solution is to remove libavcodec-ffmpeg-extra56 package, which will replace it with libavcodec-ffmpeg which stops the ffmpeg warning output.

    sudo apt remove libavcodec-ffmpeg-extra56

AskUbuntu References:

 - How to fix "library configuration mismatch": http://askubuntu.com/a/714991/8570
 - What is libavcodec-ffmpeg-extra56 package: http://askubuntu.com/a/847566/8570