Unintended parsing dependency in subpicture level information SEI

[ksuehring]

In the subpicture level information SEI the syntax element sps_num_subpics_minus1 is used as limit for a loop

			for( j = 0; j  <=  sps_num_subpics_minus1; j++ )

This seems to make it the only SEI that depends on the SPS for parsing. We believe that this was a unintentional mistake while creating document JVET-P0984 from a number of contributions during the meeting.

The dependency can easily be avoided by num_subpics_minus1 to the SEI:

subpic_level_info( payloadSize ) {	
	sli_seq_parameter_set_id					u(4)
	num_ref_levels_minus1						u(3)
	explicit_fraction_present_flag					u(1)
	sli_num_subpics_minus1						u(8)
	for( i = 0; i  <=  num_ref_levels_minus1; i++ ) {	
		ref_level_idc[ i ]					u(8)
		if( explicit_fraction_present_flag )	
			for( j = 0; j  <=  sli_num_subpics_minus1; j++ )	
				ref_level_fraction_minus1[ i ][ j ]	u(8)
	}		
}		

Note: sps_num_subpics_minus1 is coded u(8), which perfectly works with the intended byte alingment in the SEI.

[yk]

Fixed by actions taken at the 17th JVET meeting.