mtt_split_cu_vertical_flag context uses undefined variable chType

[peterderivaz]

The context derivation for mtt_split_cu_vertical_flag says it has an input of "the dual tree channel type chType" but it is not clear where this comes from.

mtt_split_cu_vertical_flag is read in the coding tree syntax which does not mention chType.

chType is mentioned in a different clause (the coding unit syntax), but it seems unlikely this is the value to be used because it has an apparent dependency on mtt_split_cu_vertical_flag via:

1. mtt_split_cu_vertical_flag is used to compute MttSplitMode
2. MttSplitMode is used to compute ModeTypeCondition
3. ModeTypeCondition is used to compute modeType
4. modeType is used to compute treeType
5. treeType is used to compute chType.

What value should be used for chType when reading the mtt_split_cu_vertical_flag syntax element?

[bbross]

Thanks and this needs indeed clarification. Will look for a solution and update the post when I have cone up with one.