US 2025/0030840 A1Published application

Cclm-based intra-prediction method and apparatus therefor

AssigneeLG Electronics Inc.

InventorsJangwon CHOI, Jin HEO, Sunmi YOO, Ling LI

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Abstract

A picture decoding method, performed by a decoding apparatus according to the present dislosure, comprises the steps of: when an intra-prediction mode of a chroma block is a cross-component linear model (CCLM) mode, deriving neighboring chroma reference samples with respect to the chroma block; deriving neighboring luma reference samples of a luma block corresponding to the chroma block and luma samples in the luma block; deriving down-sampled neighboring luma reference samples and downsampled luma samples by down sampling the neighboring luma reference samples and the luma samples, respectively; deriving a linear model parameter on the basis of the down-sampled neighboring luma reference samples and the neighboring chroma reference samples; generating prediction samples with respect to the chroma block on the basis of the linear model parameter and the down-sampled luma samples of the luma block; and reconstructing the chroma block on the basis of the prediction samples with respect to the chroma block.

Claims3

Dependent claims

A decoding apparatus for an image decoding, the decoding apparatus comprising:

a memory;
and
at least one processor connected to the memory, the at least one processor configured to:
obtain residual information for a chroma block;
derive neighboring chroma reference samples for the chroma block based on an intra prediction mode of the chroma block being a cross-component linear model (CCLM) mode;
derive neighboring luma reference samples of a luma block corresponding to the chroma block and luma samples in the luma block;
derive downsampled neighboring luma reference samples and downsampled luma samples by downsampling the neighboring luma reference samples and the luma samples;
derive a linear model parameter based on the downsampled neighboring luma reference samples and the neighboring chroma reference samples;
generate prediction samples for the chroma block based on the linear model parameter and the downsampled luma samples of the luma block;
generate residual samples for the chroma block based on the residual information for the chroma block;
reconstruct the chroma block based on the prediction samples for the chroma block and the residual samples for the chroma block;
and
perform a deblocking filtering on a reconstructed picture including the chroma block,
wherein the neighboring luma reference samples include top neighboring luma reference samples located above a top boundary of the luma block,
wherein the downsampled neighboring luma reference samples include a downsampled top neighboring luma reference sample, and
wherein based on the top boundary of the luma block being overlapped with a boundary of a coding tree unit (CTU), the downsampled top neighboring luma reference sample is derived based on an equation below,
pTopDsY
[
x
]
=
(
pY
[
2
*
x
-
1
]
[
-
1
]
+
2
*
pY
[
2
*
x
]
[
-
1
]
+
pY
[
2
*
x
+
1
]
[
-
1
]
+
2
)
>>
2
,
where pTopDsY[x] represents the downsampled top neighboring luma reference sample, x represents an x-axis direction position of the downsampled top neighboring luma reference sample, pY[2*x−1][−1], pY[2*x][−1] and pY[2*x+1][−1] represent sample values of the top neighboring luma reference samples, respectively, and a y-axis direction position of the top neighboring luma reference samples is −1.

64 more elements

An encoding apparatus for an image encoding, the encoding apparatus comprising:

a memory;
and
at least one processor connected to the memory, the at least one processor configured to:
derive neighboring chroma reference samples for a chroma block based on an intra prediction mode of the chroma block being a cross-component linear model (CCLM) mode;
derive neighboring luma reference samples of a luma block corresponding to the chroma block and luma samples in the luma block;
derive downsampled neighboring luma reference samples and downsampled luma samples by downsampling the neighboring luma reference samples and the luma samples;
derive a linear model parameter based on the downsampled neighboring luma reference samples and the neighboring chroma reference samples;
generate prediction samples for the chroma block based on the linear model parameter and the downsampled luma samples of the luma block;
derive residual samples for the chroma block based on the prediction samples for the chroma block;
and
encode image information including residual information related to the residual samples for the chroma block,
wherein the neighboring luma reference samples include top neighboring luma reference samples located above a top boundary of the luma block,
wherein the downsampled neighboring luma reference samples include a downsampled top neighboring luma reference sample, and
wherein based on the top boundary of the luma block being overlapped with a boundary of a coding tree unit (CTU), the downsampled top neighboring luma reference sample is derived based on an equation below,
pTopDsY
[
x
]
=
(
pY
[
2
*
x
-
1
]
[
-
1
]
+
2
*
pY
[
2
*
x
]
[
-
1
]
+
pY
[
2
*
x
+
1
]
[
-
1
]
+
2
)
>>
2
,
where pTopDsY[x] represents the downsampled top neighboring luma reference sample, x represents an x-axis direction position of the downsampled top neighboring luma reference sample, pY[2*x−1][−1], pY[2*x][−1] and pY[2*x+1][−1] represent sample values of the top neighboring luma reference samples, respectively, and a y-axis direction position of the top neighboring luma reference samples is −1.

62 more elements

An apparatus for transmitting data for an image, the apparatus comprising:

at least one processor configured to obtain a bitstream for the image, wherein the bitstream is generated based on deriving neighboring chroma reference samples for a chroma block based on an intra prediction mode of the chroma block being a cross-component linear model (CCLM) mode, deriving neighboring luma reference samples of a luma block corresponding to the chroma block and luma samples in the luma block, deriving downsampled neighboring luma reference samples and downsampled luma samples by downsampling the neighboring luma reference samples and the luma samples, deriving a linear model parameter based on the downsampled neighboring luma reference samples and the neighboring chroma reference samples, generating prediction samples for the chroma block based on the linear model parameter and the downsampled luma samples of the luma block, deriving residual samples for the chroma block based on the prediction samples for the chroma block, and encoding image information including residual information related to the residual samples for the chroma block to output the bitstream;
and
a transmitter configured to transmit the data comprising the bitstream,
wherein the neighboring luma reference samples include top neighboring luma reference samples located above a top boundary of the luma block,
wherein the downsampled neighboring luma reference samples include a downsampled top neighboring luma reference sample, and
wherein based on the top boundary of the luma block being overlapped with a boundary of a coding tree unit (CTU), the downsampled top neighboring luma reference sample is derived based on an equation below,
pTopDsY
[
x
]
=
(
pY
[
2
*
x
-
1
]
[
-
1
]
+
2
*
pY
[
2
*
x
]
[
-
1
]
+
pY
[
2
*
x
+
1
]
[
-
1
]
+
2
)
>>
2
,
where pTopDsY[x] represents the downsampled top neighboring luma reference sample, x represents an x-axis direction position of the downsampled top neighboring luma reference sample, pY[2*x−1][−1], pY[2*x][1] and pY[2*x+1][−1] represent sample values of the top neighboring luma reference samples, respectively, and a y-axis direction position of the top neighboring luma reference samples is −1.

54 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/905,045Filed 2 Oct 2024
Priority: 4 Oct 2018
Published: 23 Jan 2025
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H04N 19/105
Selection of coding mode or of prediction mode: selection of the reference unit for prediction within a chosen coding or prediction mode, e.g.…
H04N 19/132
Characterised by the element, parameter or selection affected or controlled by the adaptive coding: sampling, masking or truncation of coding…
H04N 19/159
Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter:…
H04N 19/176
The unit being an image region, e.g. an object: the region being a block, e.g. a macroblock

Family

Application62/741,531Us provisional application · filed 4 Oct 2018
Application17/278,473Continuation · filed 22 Mar 2021
Application17/834,532Continuation · filed 7 Jun 2022
Application18/371,319Continuation · filed 21 Sep 2023
Application18/905,045Continuation
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From the US filing history. Foreign family members aren’t listed.