Determining and hiding a replaceable period of a MP (Media Presentation). A method for determining includes receiving a first MPD (Media Presentation Description) that identifies a predetermined period and at least one media segment of the MP to be presented during the predetermined period. A determination is made as to whether the first MPD includes additional data to be resolved by an application. The additional data is provided to the application when the first MPD is determined to include the additional data. Additional period information is received from the application. A second MPD is generated based on the received additional period information. The MP is output for display to a user based on the second MPD. Each of a subset of the at least one media segment for a replaceable sub-period of the MP is replaceable with an alternate media segment.