Opened 4 years ago
Closed 4 years ago
#771 closed defect (fixed)
Truncation issue on subpicture signaling
Reported by: | geonjungko | Owned by: | |
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Priority: | minor | Milestone: | |
Component: | spec | Version: | VVC D7 vE |
Keywords: | Cc: | ksuehring, bbross, XiangLi, fbossen, jvet@… |
Description
This ticket reports an issue on semantics of subpic_ctu_top_left_x, subpic_ctu_top_left_y, subpic_width_minus1 and subpic_height_minus1.
The length of above-mentioned syntax elements and the inferred value are determined based on pic_width_max_in_luma_samples, pic_height_max_in_luma_samples and CtbSizeY.
According to the subclause “5.2 Arithmetic operators”, “/” results in the truncated integer value. Therefore, if the picture width is not a multiple of CtbSizeY, ( pic_width_max_in_luma_samples / CtbSizeY ) cannot represent the rightmost CTB. It is the same for vertical direction.
Suggested fix: change “/” to “÷” as below
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.
Change history (1)
comment:1 Changed 4 years ago by vdrugeon
- Resolution set to fixed
- Status changed from new to closed
Solved by adoption of JVET-Q0787