# US 2021/0243468 A1 · Utilization of motion information in affine mode

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- Number: US 2021/0243468 A1
- Document ID: US20210243468A1
- Status: Published application
- Kind: A1
- Application number: 17/237,450
- Filed: 2021-04-22
- Published: 2021-08-05
- Earliest claimed: 2018-10-22
- Assignees: Beijing Bytedance Network Technology Co., Ltd.; Bytedance Inc.
- Applicants: Beijing Bytedance Network Technology Co., Ltd.; Bytedance Inc.
- Inventors: Kai ZHANG; Li ZHANG; Hongbin LIU; Yue WANG
- Web page: https://patentgrep.com/patent/US20210243468A1

## CPC

- H04N 19/52: by predictive encoding
- H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
- H04N 19/139: Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/184: the unit being bits, e.g. of the compressed video stream
- H04N 19/186: the unit being a colour or a chrominance component
- H04N 19/537: Motion estimation other than block-based
- H04N 19/54: using feature points or meshes
- H04N 19/196: being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters (processing of motion vectors H04N19/513)
- H04N 19/53: Multi-resolution motion estimation; Hierarchical motion estimation
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Devices, systems and methods for utilization of motion information for affine mode are described. In a representative aspect, a video processing method includes: acquiring, during a conversion between a current block and a bitstream representation of the current block, motion information of the current block, wherein the motion information of the current block is based on at least one affine model parameter of a neighboring block of the current block; and performing, based on the motion information, the conversion between the current block and the bitstream representation of the current block.

## Claims

### Claim 1

A method of processing video data, comprising:
acquiring, during a conversion between a current block and a bitstream of the current block, motion information of the current block, wherein the motion information of the current block is based on at least one affine model parameter of a neighboring block of the current block; and
performing, based on the motion information, the conversion between the current block and the bitstream of the current block.

### Claim 2 (depends on 1)

The method of claim 1, wherein the conversion includes decoding the current block from the bitstream.

### Claim 3 (depends on 1)

The method of claim 1, wherein the conversion includes encoding the current block into the bitstream.

### Claim 4 (depends on 1)

The method of claim 1, wherein a set of affine model parameters of the current block is calculated based on the at least one affine model parameters stored with one or more neighboring blocks of the current block.

### Claim 5 (depends on 1)

The method of claim 1, wherein the at least one affine model parameter stored with one or more neighboring blocks of the current block is used to derive control points motion vectors of the current block, and wherein a set of affine model parameters of the current block is calculated based on the control points motion vectors.

### Claim 6 (depends on 1)

The method of claim 1, wherein the at least one affine model parameter stored with one or more neighboring blocks of the current block is used to derive motion vectors used in motion compensation for sub-blocks of the current block, and wherein the current block is an affine-coded block.

### Claim 7 (depends on 1)

The method of claim 1, wherein the at least one affine model parameter stored with one or more neighboring blocks of the current block is used to derive a prediction for one or more control point motion vectors (CPMVs) of the current block, which is used to predict the CPMVs of the current block when CPMVs need to be conversed.

### Claim 8 (depends on 1)

The method of claim 1, wherein the at least one affine model parameter stored with a neighboring block of the current block is inherited by the current block if the current block utilizes an affine mode merging from the neighboring block.

### Claim 9 (depends on 1)

The method of claim 1, wherein a set of affine model parameters of the current block is signaled from an encoder to a decoder; or, wherein a set of affine model parameters for the current block is predicted or inherited from one or more collocated blocks in one or multiple pictures.

### Claim 10 (depends on 1)

The method of claim 1, wherein, after a conversion of a picture is performed, affine model parameters of the picture are stored for predicting affine model parameters of a block in another picture to be conversed.

### Claim 11 (depends on 1)

The method of claim 1, wherein the at least one affine model parameter is associated with a first reference list and a second reference list, and wherein parameters for the first reference list and the second reference list are stored independently, or, parameters for the first reference list and the second reference list are stored with prediction from one to the other.

### Claim 12 (depends on 1)

The method of claim 1, wherein the performing the conversion is further based on affine model parameters and motion information stored in the neighboring M×N unit block; and
wherein the performing the conversion comprises: deriving, for motion compensation, CPMVs or motion vectors of sub-blocks of the current block.

### Claim 13 (depends on 12)

The method of claim 12, wherein the coordinate of the center position of the unit block (xm, ym) is calculated as xm=x0+M/2, ym=y0+N/2, where (x0, y0) represents the coordinate of the top-left position of the unit block.

### Claim 14 (depends on 12)

The method of claim 12, wherein for the coordinate of position (x, y), the affine model parameter of the unit block comprises four variables (a, b, e, f) corresponding to a four-parameter affine model, wherein e=mvh0, f=mvv0, and the motion vector (mvh(x,y), mvv(x,y)) is derived by:
{
m
⁢
v
h
⁡
(
x
,
y
)
=
a
⁡
(
x
-
x
⁢
m
)
-
b
⁡
(
y
-
y
⁢
m
)
+
m
⁢
v
0
h
m
⁢
v
v
⁡
(
x
,
y
)
=
b
⁡
(
x
-
x
⁢
m
)
+
a
⁡
(
y
-
y
⁢
m
)
+
m
⁢
v
0
v
where (mvh0, mvv0) represents the motion vector stored in the unit block.

### Claim 15 (depends on 12)

The method of claim 12, wherein for the coordinate of position (x, y), the affine model parameters of the unit block comprises six variables (a, b, c, d, e, f) corresponding to a six-parameter affine model, wherein e=mvh0, f=mvv0, and the motion vector (mvh(x,y), mvv(x,y)) is derived by:
{
m
⁢
v
h
⁡
(
x
,
y
)
=
a
⁢
x
+
c
⁢
y
+
m
⁢
v
0
h
m
⁢
v
v
⁡
(
x
,
y
)
=
b
⁢
x
+
d
⁢
y
+
m
⁢
v
0
v
where (mvh0, mvv0) represents the motion vector stored in the unit block.

### Claim 16 (depends on 12)

The method of claim 12, wherein for the coordinate of position (x, y), the affine model parameters of the unit block comprises six or four variables corresponding to a six-parameter or four-parameter affine model, respectively, and the motion vector (mvh(x,y), mvv(x,y)) is derived by:
{
m
⁢
v
h
⁡
(
x
,
y
)
=
a
⁢
x
+
c
⁢
y
+
m
⁢
v
0
h
m
⁢
v
v
⁡
(
x
,
y
)
=
b
⁢
x
+
d
⁢
y
+
m
⁢
v
0
v
where (mvh0, mvv0) represents the motion vector stored in the unit block.

### Claim 17 (depends on 12)

The method of claim 12, wherein CPMVs of the current block are derived from a motion vector and the affine model parameters stored in a neighbouring block, and wherein the CPMVs serve as Motion Vector Predictions (MVPs) for the signaled CPMVs of the current block, or the CPMVs are used to derive the motion vector of each sub-block of the current block used for motion compensation.

### Claim 18 (depends on 1)

The method of claim 1, further comprising:
pruning, prior to the performing the conversion, a plurality of sets of affine model parameters associated with a plurality of neighboring blocks; and
comparing, prior to the pruning, the plurality of sets of affine model parameters associated with the plurality of neighboring blocks, and deciding whether parameters {a, b, c, d, e, f} from a neighboring block are redundant with parameters {a′, b′, c′, d′, e′, f′ } from another neighboring block already in an candidate list, wherein the candidate list is an affine merge or affine AMVP candidate list.

### Claim 19

An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
acquire, during a conversion between a current block and a bitstream of the current block, motion information of the current block, wherein the motion information of the current block is based on at least one affine model parameter of a neighboring block of the current block; and
perform, based on the motion information, the conversion between the current block and the bitstream of the current block.

### Claim 20

A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:
acquiring, during a conversion between a current block and a bitstream of the current block, motion information of the current block, wherein the motion information of the current block is based on at least one affine model parameter of a neighboring block of the current block; and
generating the bitstream based on the motion information.