A method of retrieving media data, the method comprising: determining from a manifest file for media content that the media content includes a first period and a second period, that the first and second periods are continuous, and that advertisement media data is available for insertion between the first and second periods; selecting a first adaptation set in the first period from amongst a plurality of adaptation sets in the first period based at least in part on rendering characteristics signaled in the manifest file for the first adaptation set, each adaptation set comprising a respective plurality of representations of the first period of media content, each of the respective plurality of representations sharing the same rendering characteristics but having a different bitrate; retrieving media data of the first adaptation set based on the selection of the first adaptation set; based on the determination that advertisement media data is available for insertion between the first and second periods and on the selection of the first adaptation set, determining that a second adaptation set in the second period is associated with the first adaptation set, wherein the second adaptation set is one of a plurality of adaptation sets in the second period, each adaptation set comprising a respective plurality of representations of the second period of media content, each of the respective plurality of representations sharing the same rendering characteristics but having a different bitrate, wherein determining that the second adaptation set is associated with the first adaptation set comprises determining that the manifest file signals the same value for asset identifiers of the first adaptation set and the second adaptation set and the manifest file indicates that the first adaptation set and the second adaptation set have the same value for respective "@id" attributes; retrieving media data of the second adaptation set; and based on the @id attribute of representations in the first adaptation set being the same as the @id of representations in the second adaptation set, using an initialization segment of a representation of the first adaptation set as an initialization segment of a corresponding representation of the second adaptation set. determining from a manifest file for media content that the media content includes a first period and a second period, that the first and second periods are continuous, and that advertisement media data is available for insertion between the first and second periods; selecting a first adaptation set in the first period from amongst a plurality of adaptation sets in the first period based at least in part on rendering characteristics signaled in the manifest file for the first adaptation set, each adaptation set comprising a respective plurality of representations of the first period of media content, each of the respective plurality of representations sharing the same rendering characteristics but having a different bitrate; retrieving media data of the first adaptation set based on the selection of the first adaptation set; based on the determination that advertisement media data is available for insertion between the first and second periods and on the selection of the first adaptation set, determining that a second adaptation set in the second period is associated with the first adaptation set, wherein the second adaptation set is one of a plurality of adaptation sets in the second period, each adaptation set comprising a respective plurality of representations of the second period of media content, each of the respective plurality of representations sharing the same rendering characteristics but having a different bitrate, wherein determining that the second adaptation set is associated with the first adaptation set comprises determining that the manifest file signals the same value for asset identifiers of the first adaptation set and the second adaptation set and the manifest file indicates that the first adaptation set and the second adaptation set have the same value for respective "@id" attributes; retrieving media data of the second adaptation set; and based on the @id attribute of representations in the first adaptation set being the same as the @id of representations in the second adaptation set, using an initialization segment of a representation of the first adaptation set as an initialization segment of a corresponding representation of the second adaptation set.