In this invention, a device determines, at least in part based on a syntactic element contained in a scalable nesting complementary enhancement information message (sei) that is encapsulated by a network abstraction layer unit (nal) sei, if a nested message which is encapsulated by said scalable nesting message is applicable to a default data sub-stream. This default data sub-stream is an operation point representation of an operation point defined by a specified layer identifier in a nal unit header of said specific unit and by a specified time identifier. in said unit header nal. When the nested message is applicable to the default data sub-stream, the device uses said nested message in an operation performed on said default data sub-stream.