Use of chroma quantization parameter offsets in deblocking

In a computing device that implements a video decoder, a method comprising:

• receiving encoded data in a bitstream;
• and
• decoding at least some of the encoded data to reconstruct at least part of a slice of a picture, including, for each of two different chroma components of the at least part of the slice:
• setting a picture-level chroma quantization parameter (QP) offset and a slice-level chroma QP offset for the chroma component;
• and
• performing deblock filtering on the chroma component, including deriving a control parameter tC considering the picture-level chroma QP offset but not the slice-level chroma QP offset for the chroma component, wherein the deriving the control parameter tC includes:
• deriving a variable qPI=(((QPQ+QPP+1)>>1)+cqp_offset),
• wherein variables QPQ and QPP represent luma QP values for blocks on either side of an edge in the at least part of the slice on which the deblock filtering is performed, and wherein variable cqp_offset represents the picture-level chroma QP offset but not the slice-level chroma QP offset for the chroma component;
• determining a variable QPC according to a relationship between the variable QPC and the variable qPI, wherein the relationship between the variable QPC and the variable qPI is specified in a table for every value of the variable qPI, and wherein the determining the variable QPC uses a look-up operation of the variable qPI in the table;
• deriving a variable Q using the variable QPC;
• mapping the variable Q to a variable tC′;
• and
• determining the control parameter tC using the variable tC′.

A non-volatile memory or storage device having stored thereon computer-executable instructions for causing one or more processing units, when programmed thereby, to perform operations comprising:

• receiving encoded data in a bitstream;
• and
• decoding at least some of the encoded data to reconstruct at least part of a slice of a picture, including, for each of two different chroma components of the at least part of the slice:
• setting a picture-level chroma quantization parameter (QP) offset and a slice-level chroma QP offset for the chroma component;
• and
• performing deblock filtering on the chroma component, including deriving a control parameter tC considering the picture-level chroma QP offset but not the slice-level chroma QP offset for the chroma component, wherein the deriving the control parameter tC includes:
• deriving a variable qPI=(((QPQ+QPP+1)>>1)+cqp_offset),
• wherein variables QPQ and QPP represent luma QP values for blocks on either side of an edge in the at least part of the slice on which the deblock filtering is performed, and wherein variable cqp_offset represents the picture-level chroma QP offset but not the slice-level chroma QP offset for the chroma component;
• determining a variable QPC according to a relationship between the variable QPC and the variable qPI, wherein the relationship between the variable QPC and the variable qPI is specified in a table for every value of the variable qPI, and wherein the determining the variable QPC uses a look-up operation of the variable qPI in the table;
• deriving a variable Q using the variable QPC;
• mapping the variable Q to a variable tC′;
• and
• determining the control parameter tC using the variable tC′.

A computing device that implements a video decoder, wherein the computing device comprises a processing unit and memory, and wherein the computing device is configured to perform operations comprising:

• receiving encoded data in a bitstream;
• and
• decoding at least some of the encoded data to reconstruct at least part of a slice of a picture, including, for each of two different chroma components of the at least part of the slice:
• setting a picture-level chroma quantization parameter (QP) offset and a slice-level chroma QP offset for the chroma component;
• and
• performing deblock filtering on the chroma component, including deriving a control parameter tC considering the picture-level chroma QP offset but not the slice-level chroma QP offset for the chroma component, wherein the deriving the control parameter tC includes:
• deriving a variable qPI=(((QPQ+QPP+1)>>1)+cqp_offset),
• wherein variables QPQ and QPP represent luma QP values for blocks on either side of an edge in the at least part of the slice on which the deblock filtering is performed, and wherein variable cqp_offset represents the picture-level chroma QP offset but not the slice-level chroma QP offset for the chroma component;
• determining a variable QPC according to a relationship between the variable QPC and the variable qPI, wherein the relationship between the variable QPC and the variable qPI is specified in a table for every value of the variable qPI, and wherein the determining the variable QPC uses a look-up operation of the variable qPI in the table;
• deriving a variable Q using the variable QPC;
• mapping the variable Q to a variable tC′;
• and
• determining the control parameter tC using the variable tC′.