Issue in the definition of six_minus_max_num_ibc_merge_cand

[chhuanb]

The range of MaxNumIbcMergeCand is undefined after moving it to sps.

six_minus_max_num_ibc_merge_cand specifies the maximum number of IBC merging block vector prediction (BVP) candidates supported in the SPS subtracted from 6.
The maximum number of IBC merging BVP candidates, MaxNumIbcMergeCand, is derived as follows:
if( sps_ibc_enabled_flag )

MaxNumIbcMergeCand = 6 − six_minus_max_num_ibc_merge_cand (65)

else

MaxNumIbcMergeCand = 0

Suggested fix:
six_minus_max_num_ibc_merge_cand specifies the maximum number of IBC merging block vector prediction (BVP) candidates supported in the SPS subtracted from 6.
The maximum number of IBC merging BVP candidates, MaxNumIbcMergeCand, is derived as follows:
if( sps_ibc_enabled_flag )

MaxNumIbcMergeCand = 6 − six_minus_max_num_ibc_merge_cand (65)

else

MaxNumIbcMergeCand = 1

The value of MaxNumIbcMergeCand shall be in the range of 1 to 6, inclusive.

[lingli0]

I think the correct fix is to simply add one line describing the range.

---

if( sps_ibc_enabled_flag )

MaxNumIbcMergeCand = 6 − six_minus_max_num_ibc_merge_cand (65)
The value of MaxNumIbcMergeCand shall be in the range of 1 to 6, inclusive.

else

MaxNumIbcMergeCand = 0

---

The MaxNumIbcMergeCand is set to 0 when sps_ibc_enabled_flag is false so that it is more clearer to understand.

[yk]

I think the best way is the add "The value of six_minus_max_num_ibc_merge_cand shall be in the range of 0 to 5, inclusive."

Similarly, in the semantics of six_minus_max_num_merge_cand, I removed "The value of MaxNumMergeCand shall be in the range of 1 to 6, inclusive." and added "The value of six_minus_max_num_merge_cand shall be in the range of 0 to 5, inclusive.", which I believe is an editorial change but makes the text clearer.

I am making these changes to JVET-Q2001-vC. Stop me quickly if you think there is an issue with such changes.