Opened 10 years ago Closed 10 years ago #533 closed defect (invalid)Incorrect derivation of ColumnWidth and RowHeight with uniform_spacing_flag
Description
This following report is based on I0030.
When uniform_spacing_flag is used, the pseudocode for deriving ColumnWidth and RowHeight does not work properly (see equations 720 and 721). As an example, for a picture width of 23 CTBs and with three tiles, three tiles of 8 CTBs in width will be allocated.
The following pseudocode is suggested as a replacement for ColumnWidth and RowHeight derivations respectively:
if( uniform_spacing_flag ) {
} else {
}
if( uniform_spacing_flag ) {
} else {
} Change History (8)comment:1 Changed 10 years ago by DefaultCC Plugin
comment:2 followup: ↓ 3 Changed 10 years ago by shilin.xucomment:3 in reply to: ↑ 2 Changed 10 years ago by stworrall
Replying to shilin.xu:
Dear Shilin,
If we consider the more general case, 720 can be simplified as follows:
ColumnWidth[ i ] =
ColumnWidth[ i ] = ( ( i + 1  i ) * PicWidthInCtbs ) / ( num_tile_columns_minus1 + 1 )
ColumnWidth[ i ] = PicWidthInCtbs / ( num_tile_columns_minus1 + 1 )
This means that all of the ColumnWidth array values will always be the same. The same is true for the RowHeight derivation. So in the previous example (picture width of 23 CTB, three vertical tiles), all of the three tiles will have a width of 8.
Stewart. comment:4 followup: ↓ 5 Changed 10 years ago by shilin.xu
Dear Stewart,
Actually the "/" operator in JCTVCH1003_dK specifically means integer division with truncation of the result toward zero (please refer to section 5.1). Consequently we can not simplify 720 in your way due to the truncation.
Shilin comment:5 in reply to: ↑ 4 Changed 10 years ago by stworrall
Replying to shilin.xu:
Dear Shilin,
Ok, thanks for the clarification. I agree that the existing spec works.
Regards, comment:6 followup: ↓ 7 Changed 10 years ago by bbross
Can the ticket be closed then? comment:7 in reply to: ↑ 6 Changed 10 years ago by stworrall
Replying to bbross:
Yes, please feel free to close it.
Regards, comment:8 Changed 10 years ago by ksuehring
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By using the same example (a picture width of 23 CTBs and with three vertical tiles), the equations 720 and 721 in I0030 should generate three tiles whose widths are 7, 8, and 8, respectively, rather than 8, 8 and 8. Could you please tell me how you get the 8, 8 and 8 result? Thank you very much.
Shilin