A method of processing video data, the method comprising: obtaining, from a first bitstream that includes a coded representation of the video data, a Supplemental Enhancement Information, SEI, message that includes an indication of an extraction mode that was used to extract the first bitstream from a second bitstream, wherein: the first bitstream is a sub-bitstream extracted from the second bitstream according to the extraction mode, regardless of whether the extraction mode is indicated as being a first extraction mode or a second extraction mode, the first bitstream includes sufficient Network Abstraction Layer, NAL, units to decode and output pictures in a target output layer set, the first extraction mode targets self-completeness and comprises retaining in the first bitstream one or more coded pictures that are not needed for correct decoding of the target output layer set so that, if the extraction mode is indicated as being the first extraction mode, the first bitstream includes said one or more coded pictures not needed for correct decoding of the target output layer set and a conforming sub-bitstream in which said one or more coded pictures are needed is extractable from the first bitstream, and the second extraction mode targets size optimization and comprises excluding from the first bitstream one or more coded pictures that are not needed for correct decoding of the target output layer set so that, if the extraction mode is indicated as being the second extraction mode, the first bitstream does not include said one or more coded pictures not needed for correct decoding of the target output layer set and a conforming sub-bitstream in which said one or more coded pictures are needed is not extractable from the first bitstream. the first bitstream is a sub-bitstream extracted from the second bitstream according to the extraction mode, regardless of whether the extraction mode is indicated as being a first extraction mode or a second extraction mode, the first bitstream includes sufficient Network Abstraction Layer, NAL, units to decode and output pictures in a target output layer set, the first extraction mode targets self-completeness and comprises retaining in the first bitstream one or more coded pictures that are not needed for correct decoding of the target output layer set so that, if the extraction mode is indicated as being the first extraction mode, the first bitstream includes said one or more coded pictures not needed for correct decoding of the target output layer set and a conforming sub-bitstream in which said one or more coded pictures are needed is extractable from the first bitstream, and the second extraction mode targets size optimization and comprises excluding from the first bitstream one or more coded pictures that are not needed for correct decoding of the target output layer set so that, if the extraction mode is indicated as being the second extraction mode, the first bitstream does not include said one or more coded pictures not needed for correct decoding of the target output layer set and a conforming sub-bitstream in which said one or more coded pictures are needed is not extractable from the first bitstream.