A method of presenting advertising opportunities to users of a digital advertising placement system is described. In one technique, a hash table build phase involves executing vectorized instructions to determine whether a bucket in a hash table includes a free slot for inserting a key. Preferably the inverse gain applied is such that the total loop gain does not deviate too far from unity. A synchronizing method is provided to minimize a time offset between audio and video data, particularly in environments using groups of pictures. An apparatus for performing the method is also provided. A layer of dielectric material is formed on at least a portion of the first plate and substantially conforms to the predetermined shape of the first plate.