shot identification number. snapshot_id shall be in the range of 0 to 232 2, inclusive. Values of snapshot_id in the range of 0 to 255, inclusive, and in the range of 512 to 231 - 1, inclusive, may be used as determined by the application. Values of snapshot id in the range of 256 to 511, inclusive, and in the range of 231 to 232 2, inclusive, are reserved for future use by ITU-T ISO/IEC. Decoders encountering a value of snapshot in the range of 256 to 511, inclusive, or in the range of 231 to 232 2, inclusive, shall ignore (remove from the bitstream and discard) it. D.2.17 Progressive refinement segment start SEI message semantics The progressive refinement segment start SEI message specifies the beginning of a set of consecutive coded pictures that is labelled as the current picture followed by a sequence of one or more pictures of refinement of the quality of the current picture, rather than as a representation of a continually moving scene. The tagged set of consecutive coded pictures shall continue until one of the following conditions is true. When a condition below becomes true, the next slice to be decoded does not belong to the tagged set of consecutive coded pictures: The next slice to be decoded belongs to an IDR picture. num_refinement_steps_minus1 is greater than 0 and the frame num of the next slice to be decoded is (currFrameNum + num_refinement_steps_minus1 + 1) % MaxFrameNum, where currFrameNum is the value of frame_num of the picture in the access unit containing the SEI message. num_refinement_steps_minus1 is 0 and a progressive refinement segment end SEI message with the same progressive_refinement_id as the one in this SEI message is decoded. The decoding order of pictures within the tagged set of consecutive pictures should be the same as their output order. progressive_refinement_i specifies an identification number for the progressive refinement operation. progressive_refinement_id shall be in the range of 0 to 232 - 2, inclusive. Values of progressive refinement id in the range of 0 to 25