Opened 12 years ago

Closed 12 years ago

#914 closed defect (fixed)

The behavior of transform_skip_flag as 0 is not specified.

Reported by: yyu Owned by: bbross
Priority: minor Milestone: D10
Component: Text Version: D10 (L1003) v2
Keywords: Cc: bbross, wjhan, jct-vc@…

Description

In the latest HEVC spec, there is no specified behavior when transform_skip_flag is 0. We suggest the following semantics change.

Before:

transform_skip_enabled_flag equal to 1 specifies that transform_skip_flag may be present in the residual coding syntax. transform_skip_enabled_flag equal to 0 specifies that transform_skip_flag is not present in the residual coding syntax.

transform_skip_flag[ x0 ][ y0 ][ cIdx ] specifies whether a transform is applied to the associated transform block or not: The array indices x0, y0 specify the location ( x0, y0 ) of the top-left luma sample of the considered transform block relative to the top-left luma sample of the picture. The array index cIdx specifies an indicator for the colour component; it is equal to 0 for luma, equal to 1 for Cb, and equal to 2 for Cr. transform_skip_flag[ x0 ][ y0 ][ cIdx ] equal to 1 specifies that no transform will be applied to the current transform block. When transform_skip_flag[ x0 ][ y0 ][ cIdx ] is not present, it is inferred to be equal to 0.

After:
transform_skip_enabled_flag equal to 1 specifies that transform_skip_flag may be present in the residual coding syntax. transform_skip_enabled_flag equal to 0 specifies that transform_skip_flag is not present in the residual coding syntax and transform will be applied to the current transform block.

transform_skip_flag[ x0 ][ y0 ][ cIdx ] specifies whether a transform is applied to the associated transform block or not: The array indices x0, y0 specify the location ( x0, y0 ) of the top-left luma sample of the considered transform block relative to the top-left luma sample of the picture. The array index cIdx specifies an indicator for the colour component; it is equal to 0 for luma, equal to 1 for Cb, and equal to 2 for Cr. transform_skip_flag[ x0 ][ y0 ][ cIdx ] equal to 1 specifies that no transform will be applied to the current transform block. transform_skip_flag[ x0 ][ y0 ][ cIdx ] equal to 0 specifies that transform will be applied to the current transform block. When transform_skip_flag[ x0 ][ y0 ][ cIdx ] is not present, it is inferred to be equal to 0.

Change History (6)

comment:1 Changed 12 years ago by DefaultCC Plugin

  • Cc bbross wjhan jct-vc@… added

comment:2 Changed 12 years ago by bbross

  • Version changed from D9 (K1003) v11 to D10 (L1003) v1

comment:3 Changed 12 years ago by bbross

  • Milestone set to D10

comment:4 Changed 12 years ago by bbross

  • Version changed from D10 (L1003) v1 to D10 (L1003) v2

comment:5 Changed 12 years ago by bbross

"transform_skip_flag[ x0 ][ y0 ][ cIdx ] equal to 0 specifies that transform will be applied to the current transform block."
Thats not true because when one or more of the following conditions are true

  • cu_transquant_bypass_flag equal to 1
  • cu_skip_flag equal to 1
  • rqt_root_cbf equal to 0

transform_skip_flag is not present and therefore inferred to be equal to 0 but transform will not be applied because

  • cu_transquant_bypass_flag is equal to 1 or
  • cu_skip_flag equal to 1 or
  • rqt_root_cbf equal to 0

I suggest the following to define the behavior when transform_skip_flag is equal to 0:
"transform_skip_flag[ x0 ][ y0 ][ cIdx ] equal to 0 specifies that the decision whether transform is applied to the current transform block or not depends on other syntax elements. "

comment:6 Changed 12 years ago by bbross

  • Resolution set to fixed
  • Status changed from new to closed
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  • Benjamin Bross(Owner, Subscriber, Participant)
  • jct-vc@…(Subscriber)
  • karl.sharman@…(Always)
  • Karsten Suehring(Always)
  • Woo-Jin Han(Subscriber)
  • Yue Yu(Reporter)