In chapter 8.6.1 : Derivation process for quantization parameters, the following condition to derive of qPY_prev is incorrect :

"The current quantization group is the first quantization group in a coding tree block row and entropy_coding_sync_enabled_flag is equal to 1." (taking into account ticket #721)

According to entropy_coding_sync_enabled_flag definition :

"entropy_coding_sync_enabled_flag equal to 1 specifies that a specific synchronization process for context variables is invoked before decoding the first coding tree block of a row of coding tree blocks in each tile..."

the condition should be :

The current quantization group is the first quantization group in a coding tree block row of a tile and entropy_coding_sync_enabled_flag is equal to 1.

I beleive a recent 'cleanup' of the 'ctbAddr' calculation has added brackets in the wrong place. Under bullet points 2 and 3, the address calculation is currently;-

tmpX = xQg − ( 1 >> Log2MinTrafoSize ) tmpY = yQg >> Log2MinTrafoSize minTbAddrA = MinTbAddrZs[ tmpX ][ tmpY ] ctbAddrA = ( minTbAddrA >> 2 ) * (Log2CtbSizeY − Log2MinTrafoSize) (8 249)

I beleive the brackets in the calculation of tmpX(/tmpY) and ctbAddrA(/B) should be;-

tmpX = (xQg − 1) >> Log2MinTrafoSize

ctbAddrA = minTbAddrA >> ( 2 * (Log2CtbSizeY − Log2MinTrafoSize) ) (8 249)

(To calculate the location of transform block to the left/above, and then use shift as an equivalence to divide by the number of transform blocks in a CTU).

In 8.6.1, text said: "The current quantization group is the first quantization group in a coding tree block row and tiles_or_entry_coding_sync_idc is equal to 2."

But tiles_or_entry_coding_sync_idc is not defined.

Suggestion: Replace "tiles_or_entry_coding_sync_idc is equal to 2" by "entropy_coding_sync_enabled_flag is equal to 1"