This extension works with ffmpeg version 0.5 available in RPM Fusion (free) repository and PHP 5.3.2. This RPM is build from the SVN snapshot (version 0.6.3, revision 676).

Installation :

yum --enablerepo=remi install php-ffmpeg

For now, the old version 0.4.9 available in old fedora version (and EL) is not compatible.

I'm waiting for your feedbacks, and if this extension is maintainable (ffmpeg-php upstream is not really active, while ffmpeg is), I will perhaps submit it for RPM Fusion.