Opened 5 years ago
Closed 5 years ago
#790 closed defect (fixed)
Log2 issue in subpicture signaling
| Reported by: | zhangkai | Owned by: | |
|---|---|---|---|
| Priority: | minor | Milestone: | |
| Component: | spec | Version: | VVC D7 vE |
| Keywords: | Cc: | ksuehring, bbross, XiangLi, fbossen, jvet@… |
Description
With the signaling of subpictures, we have
subpic_ctu_top_left_x[ i ] specifies horizontal position of top left CTU of i-th subpicture in unit of CtbSizeY. The length of the syntax element is Ceil( Log2( pic_width_max_in_luma_samples / CtbSizeY ) ) bits. When not present, the value of subpic_ctu_top_left_x[ i ] is inferred to be equal to 0.
subpic_ctu_top_left_y[ i ] specifies vertical position of top left CTU of i-th subpicture in unit of CtbSizeY. The length of the syntax element is Ceil( Log2( pic_height_max_in_luma_samples / CtbSizeY ) ) bits. When not present, the value of subpic_ctu_top_left_y[ i ] is inferred to be equal to 0.
subpic_width_minus1[ i ] plus 1 specifies the width of the i-th subpicture in units of CtbSizeY. The length of the syntax element is Ceil( Log2( pic_width_max_in_luma_samples / CtbSizeY ) ) bits. When not present, the value of subpic_width_minus1[ i ] is inferred to be equal to Ceil( pic_width_max_in_luma_samples / CtbSizeY ) − 1.
subpic_height_minus1[ i ] plus 1 specifies the height of the i-th subpicture in units of CtbSizeY. The length of the syntax element is Ceil( Log2( pic_height_max_in_luma_samples / CtbSizeY ) ) bits. When not present, the value of subpic_height_minus1[ i ] is inferred to be equal to Ceil( pic_height_max_in_luma_samples / CtbSizeY ) − 1.
pic_width_max_in_luma_samples / CtbSizeY is equal to zero if pic_width_max_in_luma_samples < CtbSizeY, which makes Log2() meaningless.
Log2( pic_width_max_in_luma_samples / CtbSizeY ) should be changed to Log2( (pic_width_max_in_luma_samples + CtbSizeY - 1)/ CtbSizeY )
Log2( pic_height_max_in_luma_samples / CtbSizeY ) should be changed to Log2( (pic_height_max_in_luma_samples + CtbSizeY - 1)/ CtbSizeY )
Change history (2)
comment:1 Changed 5 years ago by LIJINGYA
comment:2 Changed 5 years ago by vdrugeon
- Resolution set to fixed
- Status changed from new to closed
Solved by adoption of JVET-Q0787
Yes I agree with the change. the code is also implemented in this way.
Just some add-on from Ticket #781, it would be more comprehensive to have:
to ensure that it covers cases of very small (<=128x128) frame sizes.