Systems and methods for deriving quantization parameters for video blocks in video coding

1. A method of coding of video data, the method comprising:

deriving a predicted luma quantization parameter by using a tree type specifying whether a single tree or a dual tree is used to partition a coding tree; and

generating a luma quantization parameter by using the predicted luma quantization parameter, wherein:

the predicted luma quantization parameter is set equal to a luma quantization parameter of a coding unit containing a luma coding block covering a neighboring location when a first condition of a current quantization group is true and a second condition of a neighboring block availability is true, and

the neighboring location is located above the current quantization group.

2. The method of claim 1 , wherein the first condition of the current quantization group is true if the current quantization group is a first quantization group in a coding tree block row within a tile.

3. The method of claim 1 , wherein the neighboring block availability is derived by using a current location set equal to a coding block location and the neighboring location.

4. The method of claim 1 , wherein the current quantization group is a rectangular region inside a coding tree block that shares a same predicted luma quantization parameter as the current quantization group.

5. The method of claim 1 , wherein the predicted luma quantization parameter is derived when the tree type is equal to the single tree or a dual tree luma, wherein the dual tree luma is processed when the dual tree is used.

6. The method of claim 1 , wherein:

the neighboring location is represented as (xQg, yQg−1),

xQg is a horizontal position specifying a top-left sample of the current quantization group relative to a top-left luma sample of a current picture, and

yQg is a vertical position specifying the top-left sample of the current quantization group relative to the top-left luma sample of the current picture.

7. The method of claim 1 , wherein the second condition of the neighboring block availability is true if an output of one availability derivation process invoked with a current location set equal to a coding block location and the neighboring location is true.

8. The method of claim 1 , wherein:

the first condition of the current quantization group is true if the current quantization group is a first quantization group in a coding tree block row within a tile, and

the second condition of the neighboring block availability is true if an output of one availability derivation process invoked with a current location set equal to a coding block location and the neighboring location is true.

9. A method of decoding of image data, the method comprising:

deriving a predicted luma quantization parameter by using a tree type specifying whether a single tree or a dual tree is used to partition a coding tree; and

generating a luma quantization parameter by using the predicted luma quantization parameter, wherein:

the predicted luma quantization parameter is set equal to a luma quantization parameter of a coding unit containing a luma coding block covering a neighboring location when a first condition of a current quantization group is true and a second condition of a neighboring block availability is true, and

the neighboring location is located above the current quantization group.

10. The method of claim 1 , wherein:

the first condition of the current quantization group is true if the current quantization group is a first quantization group in a coding tree block row within a tile, and

the second condition of the neighboring block availability is true if an output of one availability derivation process invoked with a current location set equal to a coding block location and the neighboring location is true.

11. The method of claim 9 , wherein the neighboring block availability is derived by using a current location set equal to a coding block location and the neighboring location.

12. The method of claim 9 , wherein the current quantization group is a rectangular region inside a coding tree block that shares a same predicted luma quantization parameter as the current quantization group.

13. The method of claim 9 , wherein the predicted luma quantization parameter is derived when the tree type is equal to the single tree or a dual tree luma, wherein the dual tree luma is processed when the dual tree is used.

14. The method of claim 9 , wherein:

the neighboring location is represented as (xQg, yQg−1),

xQg is a horizontal position specifying a top-left sample of the current quantization group relative to a top-left luma sample of a current picture, and

yQg is a vertical position specifying the top-left sample of the current quantization group relative to the top-left luma sample of the current picture.

15. A device comprising:

one or more processors; and

one or more non-transitory computer-readable media coupled to the one or more processors and storing one or more computer-executable instructions that, when executed by at least one of the one or more processors, cause the device to:

derive a predicted luma quantization parameter by using a tree type specifying whether a single tree or a dual tree is used to partition a coding tree; and

generate a luma quantization parameter by using the predicted luma quantization parameter, wherein:

the predicted luma quantization parameter is set equal to a luma quantization parameter of a coding unit containing a luma coding block covering a neighboring location when a first condition of a current quantization group is true and a second condition of a neighboring block availability is true, and

the neighboring location is located above the current quantization group.