What's /system/vendor/lib/liboemcrypto.so?
That's (part of the) implementation of Android's "modular DRM", which came into being in Android 4.3 (API level 18) -- see MediaDrm. Essentially it's the component that allows media player apps, under certain conditions, to play back DRM-protected contents.

If you are running on Android 4.2 or lower, however, you're probably out of luck. To confirm, you can install an app like DRM Info, which will tell you whether any DRM library is installed on your system. If not, am afraid there's nothing you can do on this specific device.