to 1 indicates that all IROIs for the current scalable layer are aligned on a fixed-size grid as specified in the following and that the syntax elements grid_width_in_mbs_minus1[i] and grid_width_in_mbs_minus1[i] for the current scalable layer are present in the scalability information SEI message. iroi_grid_flag[ ] equal to 0 indicates that the IROIs for the current scalable layer may or may not be aligned on a fixed- size grid. All scalable layers with the same value of dependency_i id[ for which scalability information is present in the scalability information SEI message and for which iroi_division_info_present_flag[i]is equal to 1 shall have the same value of iroi_grid_flag[ grid_width_in_mbs_minus1[i] and grid_height_in_mbs_minus1[ indicate the size of the IROI grid for the current scalable layer. When frame_mbs_only_flag is equal to 0 for any primary coded VCL NAL unit of the current scalable layer, (grid_height_in_mbs_minus1[i] shall be equal to 0. The value of grid_width_in_mbs_minus1[i] shall be in the range of 0 to FrmWidthInMbs[ - 1, inclusive. The value of grid_height_in_mbs_minus1[i]shall be in the range of 0 to FrmHeightInMbs[ inclusive. Let numX and numY be equal to FrmWidthInMbs[i]+grid_width_in_mbs_minus1[i]) grid_width_in_mbs_minus1[i]+1 FrmHeightInMbs[i]+grid_height_in_mbs_minus1[i]) ( _height_in_mbs_minus1[i]+1) respectively. The layer pictures with dependency_id equal to dependency_id[ are partitioned into (numX * numY) IROIs. Let (xI[k],yI[k]) be the location of the top-left luma sample of the k-th IROI relative to the top-left luma sample of the layer picture and let w[ k ] and k ] be the width and height, in luma samples, of the k-th IROI in the layer picture. With field_pic_flag being the slice header syntax element for a particular layer picture with dependency id equal to dependency_id[i], the location of the top-left luma sample and the width and height of the k-th IROI, with k=0..(numX* numY - 1), are given by xI[k] 16 *(k%numX)* ( grid_width_in_mbs_minus1[i]+1 (G-377) yI[k]=16 (k/nu