A computer implemented method for enabling content providers to identify and customize placement opportunities is disclosed, comprising the steps of processing instructions to customize a pre-existing at least one of an audio and video datastream comprising at least one predefined time interval for content, identifying at least one time interval for a placement opportunity in the at least one of an audio and video datastream; altering at least one characteristic of the at least one time interval for a placement opportunity in accordance with the instructions; assembling the altered at least one time interval for a placement opportunity and at least one time interval for content into a list that represents an altered at least one of an audio and video datastream; and delivering the list to a distribution system for playing the altered at least one of an audio and video datastream. The at least one time interval for a placement opportunity may distinct from or coincident with the at least one time interval for content. The placement opportunity may be at least one of content and an advertising placement opportunity. The content may be entertainment content comprising at least one of video, audio, and interactive overlays. The at least one characteristic may be the duration of or the number of the at least one time interval for a placement opportunity. The list may be one of a playlist and a schedule.