Use of chroma quantization parameter offsets in deblocking
AssigneeMicrosoft Technology Licensing, LLC
InventorGary J. Sullivan
Life of this patent
Estimating the term…
Abstract
Innovations in use of chroma quantization parameter (“QP”) offsets when determining a control parameter for deblock filtering. For example, as part of encoding, an encoder sets a picture-level chroma QP offset and slice-level chroma QP offset for encoding of a slice of a picture. The encoder also performs deblock filtering of at least part of the slice, where derivation of a control parameter considers only the picture-level chroma QP offset. The encoder outputs at least part of a bitstream including the encoded content. As part of decoding, a corresponding decoder sets a picture-level chroma QP offset and a slice-level chroma QP offset for decoding of a slice of a picture, but derivation of a control parameter for deblock filtering considers only the picture-level chroma QP offset.
Claims19
A non-volatile memory or storage device having stored thereon at least part of a bitstream including encoded image or video content for which values of quantization parameter (QP) vary according to a relationship between a luma component and chroma components, wherein the bitstream is organized to facilitate decoding of at least some of the encoded content by operations comprising:
- setting a picture-level chroma QP offset and a slice-level chroma QP offset for decoding of a slice of a picture;
- for the decoding of the slice, using the picture-level chroma QP offset and the slice-level chroma QP offset to regulate inverse quantization, according to a chroma QP, of transform coefficients for one or more portions of the slice;
- and
- performing deblock filtering of at least part of the slice, wherein derivation of a control parameter for the deblock filtering of the at least part of the slice considers the picture-level chroma QP offset but not the slice-level chroma QP offset, the control parameter depending on a variable qPI derived as:
- 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 deblock filtering is performed, wherein variable cqp_offset represents the picture-level chroma QP offset, and wherein the variable qPI is used to determine a variable QPc that is used in the derivation of the control parameter.
A computing system that comprises one or more processing units and memory, wherein the computing system implements an image or video encoder configured to encode image or video content for which values of quantization parameter (QP) vary according to a relationship between a luma component and chroma components, the encoder comprising:
- a controller configured to set a picture-level chroma QP offset and a slice-level chroma QP offset for encoding of a slice of a picture;
- a quantizer configured to, for the encoding of the slice, use the picture-level chroma QP offset and the slice-level chroma QP offset to regulate quantization, according to a chroma QP, of transform coefficients for one or more portions of the slice;
- a deblock filter configured to perform deblock filtering of at least part of the slice, wherein derivation of a control parameter for the deblock filtering of the at least part of the slice considers the picture-level chroma QP offset but not the slice-level chroma QP offset, the control parameter depending on a variable qPI derived as:
- 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 deblock filtering is performed, wherein variable cqp_offset represents the picture-level chroma QP offset, and wherein the variable qPI is used to determine a variable QPc that is used in the derivation of the control parameter;
- and
- a buffer configured to store at least part of a bitstream including encoded content.
A computing system that comprises one or more processing units and memory, wherein the computing system implements an image or video decoder comprising:
- a buffer configured to store at least part of a bitstream including encoded image or video content for which values of quantization parameter (QP) vary according to a relationship between a luma component and chroma components;
- and
- a parser configured to parse, from the bitstream, one or more syntax elements that indicate a picture-level chroma QP offset and one or more syntax elements that indicate a slice-level chroma QP offset for decoding of a slice of a picture;
- an inverse quantizer configured to, for the decoding of the slice, use the picture-level chroma QP offset and the slice-level chroma QP offset to regulate inverse quantization, according to a chroma QP, of transform coefficients for one or more portions of the slice;
- and
- a deblock filter configured to perform deblock filtering of at least part of the slice, wherein derivation of a control parameter for the deblock filtering of the at least part of the slice considers the picture-level chroma QP offset but not the slice-level chroma QP offset, the control parameter depending on a variable qPI derived as:
- 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 deblock filtering is performed, wherein variable cqp_offset represents the picture-level chroma QP offset, and wherein the variable qPI is used to determine a variable QPc that is used in the derivation of the control parameter.
Dependencies are inferred from the claim text.