Use of chroma quantization parameter offsets in deblocking

摘要

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.

主权项

1. A computing device that implements an image or video encoder, wherein the computing device comprises a processing unit and memory, and wherein the computing device is configured to perform operations comprising:
encoding 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 encoding includes:
setting a picture-level chroma QP offset and a slice-level chroma QP offset for encoding of a slice of a picture;storing the picture-level chroma QP offset; andperforming 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, wherein the variable qPI is used to determine a variable QPC that is used in the derivation of the control parameter, and wherein values of the control parameter are derived separately for two different chroma components of the picture; and
outputting at least part of a bitstream including the encoded content, wherein the picture-level chroma QP offset is separately signaled for the two different chroma components, and wherein bitstream syntax permits signaling of different slice-level chroma QP offsets for different slices of the picture.