id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
1378	Incorrect pps_tile_idx_delta_val[i] range	kerzhy		"In 7.4.3.5 the ranges of '''pps_tile_idx_delta_val[i]''' are specified from '''-NumTilesInPic + 1''' to '''NumTilesInPic - 1''' inclusive

So, if we want to get min pps_tile_idx_delta_val[i] (by spec) we need to take bottom right tile and than the top left tile. Only in these cases we will get -NumTilesInPic + 1 

But we know from 7.4.8:
    ""The shapes of the slices of a picture shall be such that each CTU, when decoded, shall have its entire left boundary and entire top boundary consisting of a picture boundary or consisting of boundaries of previously decoded CTU(s).""

So, if we have more than 1 tile (only in this case pps_tile_idx_delta_val[i] can exist due to 7.3.2.5 from spec) it is unable to reach pps_tile_idx_delta_val[i] = -NumTilesInPic + 1 because all CTUs in current tile need to have specified top&left boundaries, but if we will start from last tile (bottom right) condition from 7.4.8 don't be met.

The min value of pps_tile_idx_delta_val[i] we can get, is '''-NumTilesInPic + 3''', like in this case:
[https://drive.google.com/file/d/11rE5vrS77feozXJfb3NMqpmBgJ31zacs/view?usp=sharing]

About max value: if we accept, that pps_tile_delta_idx_val[i] can be applied in raster-scan case (I haven't found any contradiction in spec), in that way max value = NumTilesInPic - 1 is correct (i.e. we have 2 tiles in pic, so 2nd tileIdx (=1) - 1st tileIdx(=0) = 1 = NumTilesInPic(2) - 1). But using pps_tile_delta_idx_present_flag for case of 2 tiles makes no sence.

And if we consider more than 2 tiles, the max value will be NumTilesInPic - 3 (by analogy with min value, with the only difference that firstly we need to take 3rd and then 2nd tile (check tile scan order)).

After all of this, I suppose that at least min range boundary needs to be corrected, and '''pps_tile_idx_delta_val[i]''' range should be from '''-NumTilesInPic + 3''' to '''NumTilesInPic - 1''' (or even from '''-NumTilesInPic + 3''' to '''NumTilesInPic - 3''')."	defect	closed	minor		spec		worksforme	tile delta	ksuehring bbross XiangLi fbossen jvet@… kirillsuverov@…