Serious problem

The screen shot above has nothing to do with ffmpeg. that is a separate error occurring somwhere else.
This error in the screen shot is vbseo 3.3.0 running on php 5.3. 5.3 didn't exist when vbseo 3.3 was released.

You can try rebuilding apache on your server with php 5.2.x latest build which will fix all these warnings.

So you suggest me to downgrade php version with latest 5.2.x version.
Should I than also do step back what was told in this thread:

vBSEO Sitemap 2.5: PHP Deprecated: Function set_magic_quotes_runtime() is deprecated


because I did that to fix problem with sitemap.

You can but you don't have to. That is simply warning display message set up. it has no effect on the php code being executed.