CBF flags syntax and semantics

[chernyak]

CBF flags signalling in transform_unit has a typo in condition and doesn't cover implicit TU partitioning. Suggested modification:

if( ( IntraSubPartitionsSplitType == ISP_NO_SPLIT &&

!( cu_sbt_flag && ( ( subTuIndex = = 0 && cu_sbt_pos_flag ) | | ( subTuIndex = = 1 && !cu_sbt_pos_flag ) ) ) &&

((CuPredMode[ x0 ][ y0 ] == MODE_INTRA | | tu_cbf_cb[x0 ][ y0 ] | | tu_cbf_cr[ x0 ][ y0 ] ) | | (CbWidth[ x0 ][ y0 ] > MaxTbSizeY | | CbHeight[ x0 ][ y0 ] > MaxTbSizeY ) ) )

| |

((IntraSubPartitionsSplitType != ISP_NO_SPLIT) && ( subTuIndex < NumIntraSubPartitions − 1 | | InferTuCbfLuma ) ) )

Semantics part doesn't cover all possible cases of tu_cbf_luma deriving.
Suggested modification:

tu_cbf_luma[ x0 ][ y0 ] equal to 1 specifies that the luma transform block contains one or more transform coefficient levels not equal to 0. 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.
When tu_cbf_luma[ x0 ][ y0 ] is not present in the current TU, its value is inferred as follows:

• If cu_sbt_flag is equal to 1 and any of the following conditions is true, tu_cbf_luma[ x0 ][ y0 ] is inferred to be equal to 0.
  • subTuIndex is equal to 0 and cu_sbt_pos_flag is equal to 1;
  • subTuIndex is equal to 1 and cu_sbt_pos_flag is equal to 0;
• Otherwise, tu_cbf_luma[ x0 ][ y0 ] is inferred to be equal to 1.

The "current CU" to "current TU" change needs to be done also for the other TU cbfs as well.

[bbross]

Fixed in D5 v8