Each packaging format has its own conventions, in an RPM spec, it is customary to declare dep on ldconfig in this way.
No point declaring a dep on glibc, since ALL RHEL based distros already include it.
That should be fine now, however, post updating to the package I pushed today.
Also, we DO support both Debian and Ubuntu as well and provide debs for them, if you prefer Ubuntu, why not use that?
Mencoder depends on i686 libs because it has no full port to 64bit. Some of its libs are 32bit only.