Granted Patent B2

US 12,464,119 · App. 18/774,707 · Granted Nov 4, 2025

Inventor: Masato Shima (Tokyo, JP)

Assignee: Canon Kabushiki Kaisha

H04N19/105H04N19/124H04N19/176H04N19/186H04N19/61

Abstract

Claims (53)

1 . An image encoding device that generates a bitstream by encoding an image having a plurality of components including at least a luma component and a chroma component, the image encoding device comprising:

a determination unit configured to determine whether or not to perform transform processing on the chroma component in a block to be encoded; and

an encoding unit configured to encode the chroma component in the block to be encoded using a first quantization parameter corresponding to the chroma component in the block to be encoded when the determination unit determines that transform processing is performed on the chroma component in the block to be encoded,

wherein, when the first quantization parameter is smaller than a reference value and the determination unit determines that transform processing is not performed on the chroma component in the block to be encoded, the encoding unit encodes the chroma component in the block to be encoded using the reference value as a quantization parameter,

wherein the reference value is commonly used in the plurality of components, wherein the reference value is a value defining a minimum value of the quantization parameter when the determination unit determines that transform processing is not performed on the chroma component in the block to be encoded,

wherein the encoding unit encodes, into the bitstream, information indicating difference between a value of the quantization parameter corresponding to a quantization step being 1 and the reference value as information indicating the reference value,

wherein the value of the quantization parameter corresponding to the quantization step being 1 is 4, and

wherein, the image encoding device further comprises a prediction unit configured to perform prediction on the block to be encoded.

2 . An image decoding device that decodes a bitstream generated by encoding an image having a plurality of components including a luma component and a chroma component, the image decoding device comprising:

a derivation unit configured to derive a first quantization parameter corresponding to the chroma component in a block to be decoded based on information decoded from the bitstream;

a determination unit configured to determine whether or not to perform transform processing on the chroma component in the block to be decoded; and

a decoding unit configured to decode the chroma component in the block to be decoded using the first quantization parameter when the determination unit determines that transform processing is performed on the chroma component in the block to be decoded,

wherein, when the first quantization parameter is smaller than a reference value and the determination unit determines that transform processing is not performed on the chroma component in the block to be decoded, the decoding unit decodes the chroma component in the block to be decoded using the reference value as a quantization parameter,

wherein the reference value is commonly used in the plurality of components, wherein the reference value is a value defining a minimum value of the quantization parameter when the determination unit determines that transform processing is not performed on the chroma component in the block to be decoded,

wherein the decoding unit decodes, from the bitstream, information indicating difference between a value of the quantization parameter corresponding to a quantization step being 1 and the reference value as information indicating the reference value,

wherein the value of the quantization parameter corresponding to the quantization step being 1 is 4, and

wherein, the image decoding device further comprises a prediction unit configured to perform prediction on the block to be decoded.

3 . An image encoding method that generates a bitstream by encoding an image having a plurality of components including at least a luma component and a chroma component, the image encoding method comprising:

determining whether or not to perform transform processing on the chroma component in a block to be encoded;

encoding the chroma component in the block to be encoded using a first quantization parameter corresponding to the chroma component in the block to be encoded when it is determined that transform processing is performed on the chroma component in the block to be encoded; and

when the first quantization parameter is smaller than a reference value and it is determined that transform processing is not performed on the chroma component in the block to be encoded, encoding the chroma component in the block to be encoded using the reference value as a quantization parameter,

wherein the reference value is commonly used in the plurality of components, wherein the reference value is a value defining a minimum value of the quantization parameter when it is determined that transform processing is not performed on the chroma component in the block to be encoded,

wherein the image encoding method further comprises encoding, into the bitstream, information indicating difference between a value of the quantization parameter corresponding to a quantization step being 1 and the reference value as information indicating the reference value,

wherein the value of the quantization parameter corresponding to the quantization step being 1 is 4 and

wherein, the image encoding method further comprises performing prediction on the block to be encoded.

4 . An image decoding method that decodes a bitstream generated by encoding an image having a plurality of components including a luma component and a chroma component, the image decoding method comprising:

deriving a first quantization parameter corresponding to the chroma component in a block to be decoded based on information decoded from the bitstream;

determining whether or not to perform transform processing on the chroma component in the block to be decoded;

decoding the chroma component in the block to be decoded using the first quantization parameter, when it is determined that transform processing is performed on the chroma component in the block to be decoded; and

decoding, when the first quantization parameter is smaller than a reference value and it is determined that transform processing is not performed on the chroma component in the block to be decoded, the chroma component in the block to be decoded using the reference value as a quantization parameter,

wherein the reference value is commonly used in the plurality of components,

wherein the reference value is a value defining a minimum value of the quantization parameter when it is determined that transform processing is not performed on the chroma component in the block to be decoded,

wherein the image decoding method further comprises decoding, from the bitstream, information indicating difference between a value of the quantization parameter corresponding to a quantization step being 1 and the reference value as information indicating the reference value,

wherein the value of the quantization parameter corresponding to the quantization step being 1 is 4, and

wherein, the image decoding method further comprises performing prediction on the block to be decoded.

5 . A non-transitory computer readable medium storing a computer-executable program for causing a computer to perform an image encoding method for encoding an image in units of blocks, the image encoding method comprising:

determining whether or not to perform transform processing on the chroma component in a block to be encoded;

encoding the chroma component in the block to be encoded using a first quantization parameter corresponding to the chroma component in the block to be encoded when it is determined that transform processing is performed on the chroma component in the block to be encoded; and

when the first quantization parameter is smaller than a reference value and it is determined that transform processing is not performed on the chroma component in the block to be encoded, encoding the chroma component in the block to be encoded using the reference value as a quantization parameter,

wherein the reference value is commonly used in the plurality of components, wherein the reference value is a value defining a minimum value of the quantization parameter when it is determined that transform processing is not performed on the chroma component in the block to be encoded,

wherein the image encoding method further comprises encoding, into the bitstream, information indicating difference between a value of the quantization parameter corresponding to a quantization step being 1 and the reference value as information indicating the reference value,

wherein the value of the quantization parameter corresponding to the quantization step being 1 is 4 and

wherein, the image encoding method further comprises performing prediction on the block to be encoded.

6 . A non-transitory computer readable medium storing a computer-executable program for causing a computer to perform an image decoding method that decodes a bitstream generated by encoding an image having a plurality of components including a luma component and a chroma component, the image decoding method comprising:

deriving a first quantization parameter corresponding to the chroma component in a block to be decoded based on information decoded from the bitstream;

determining whether or not to perform transform processing on the chroma component in the block to be decoded;

decoding the chroma component in the block to be decoded using the first quantization parameter, when it is determined that transform processing is performed on the chroma component in the block to be decoded; and

decoding, when the first quantization parameter is smaller than a reference value and it is determined that transform processing is not performed on the chroma component in the block to be decoded, the chroma component in the block to be decoded using the reference value as a quantization parameter,

wherein the reference value is commonly used in the plurality of components,

wherein the reference value is a value defining a minimum value of the quantization parameter when it is determined that transform processing is not performed on the chroma component in the block to be decoded,

wherein the image decoding method further comprises decoding, from the bitstream, information indicating difference between a value of the quantization parameter corresponding to a quantization step being 1 and the reference value as information indicating the reference value,

wherein the value of the quantization parameter corresponding to the quantization step being 1 is 4, and

wherein, the image decoding method further comprises performing prediction on the block to be decoded.

Priority Claims (1)

Continuity (3)

References Cited (13)