_sample_value_match_flag should be 1. pan_scan_rect_flag equal to 0 specifies that pan_scan_rect_id is not present. pan_scan_rect_flag equal to 1 specifies that pan_scan_rect_id is present. pan_scan_rect_id indicates that the specified slice group set covers at least the pan-scan rectangle identified by pan_scan_rect_id within the target picture set. NOTE 3 - Multiple motion_constrained_slice_group_set SEI messages may be associated with the same IDR picture. Consequently, more than one slice group set may be active within a target picture set. NOTE The size, shape, and location of the slice groups in the slice group set may change within the target picture set. D.2.20 Film grain characteristics SEI message semantics This SEI message provides the decoder with a parameterised model for film grain synthesis. For example, an encoder may use the film grain characteristics SEI message to characterise film grain that was present in the original source video material and was removed by pre-processing filtering techniques. Synthesis of simulated film grain on the decoded images for the display process is optional and does not affect the decoding process specified in this Recommendation International Standard. If synthesis of simulated film grain on the decoded images for the display process is performed, there is no requirement that the method by which the synthesis is performed be the same as the parameterised model for the film grain as provided in the film grain characteristics SEI message. NOTE 1 - The display process is not specified in this Recommendation International Standard. NOTE 2 - The SMPTE specification "SMPTE RDD 5-2006. Film Grain Technology - Specifications for H.264/MPEG-4 AVC Bitstreams." specifies a film grain simulator based on the information provided in the film grain characteristics SEI message. Rec. ITU-T H.264 (01/2012) film_grain_characteristics_cancel_flag equal to 1 indicates that the SEI message cancels the persistence of any previous film grain characteristics SEI message in output order. f