1. A method for decoding a video, the method comprising: 5 obtaining a residual coefficient of a current transform block; inverse-quantizing the residual coefficient; determining a transform type set of the current transform block; and 10 obtaining a residual sample of the current transform block by performing inverse-transform for the current transform block based on the transform type set, characterized in that: 15 in response to a case where a coding block including the current transform block is partitioned into two transform blocks, the transform type set of the current transform block is determined differently between when the coding block is 20 partitioned in a horizontal direction and when the coding block is partitioned in a vertical direction, and the coding block is obtained based on a tree- based block division including at least one of a 25 quad division or a binary division.

2. The method of claim 1, wherein the transform type set is constituted of a first transform type and a second transform type, 56 wherein each of the first transform type and the second transform type is representative of DCT (Discrete Cosine Transform) 2, DST (Discrete Sine Transform) 7 or DCT 8, 5 wherein the first transform type is used for a horizontal transform for the current transform block, and wherein the second transform type is used for a vertical transform for the current transform 10 block.

3. The method of claim 1, wherein the transform type set of the current transform block is determined differently between when the current transform block 15 is one of the two transform blocks and when the current transform block is the other of the two transform blocks.

4. The method of claim 1, wherein the method 20 comprises: determining whether the transform type set of the current transform block is determined explicitly or implicitly, wherein when it is determined that the 25 transform type set of the current transform block is determined explicitly, the transform type set of the current transform block is determined based on index information explicitly signaled via a bitstream, the index information specifying one of 57 a plurality of transform type sets, and wherein when it is determined that the transform type set of the current transform block is determined implicitly, the transform type set of 5 the current transform block is determined without parsing the index information from the bitstream.

5. The method of claim 4, wherein the determination of whether the transform type set of the current 10 transform block is determined explicitly or implicitly is based on a comparison between the size of the current transform block and a threshold size.

6. A method for encoding a video, the method 15 comprising: obtaining a residual sample of a current transform block; determining a transform type set of the current transform block; 20 obtaining a transform coefficient of the current transform block by performing transform for the current transform block based on the transform type set; and obtaining a residual coefficient by quantizing 25 the transform coefficient, characterized in that: in response to a case where a coding block including the current transform block is partitioned into two transform blocks, the transform type set 58 of the current transform block is determined differently between when the coding block is partitioned in a horizontal direction and when the coding block is partitioned in a vertical direction, 5 and the coding block is obtained based on a tree- based block division including at least one of a quad division or a binary division. 10 7. A method of storing or transmitting compressed video data generated by an encoding method of claim

6. 8. A device for transmitting compressed video data, 15 comprising: a processor configured to obtain the compressed video data; and a transmitter configured to transmit the compressed video data, 20 wherein obtaining the compressed video data comprises: obtaining a residual sample of a current transform block; determining a transform type set of the current 25 transform block; obtaining a transform coefficient of the current transform block by performing transform for the current transform block based on the transform type set; and 59 obtaining a residual coefficient by quantizing the transform coefficient, characterized in that: in response to a case where a coding block 5 including the current transform block is partitioned into two transform blocks, the transform type set of the current transform block is determined differently between when the coding block is partitioned in a horizontal direction and when the 10 coding block is partitioned in a vertical direction, and the coding block is obtained based on a tree- based block division including at least one of a quad division or a binary division. 15 60 Date 10 July 2025 MALATHI LAKSHMIKUMARAN IN/PA-1433 Agent for the Applicant To, The Controller of Patents The Patent Office at New Delhi ABSTRACT METHOD AND APPARATUS FOR PROCESSING VIDEO SIGNAL A method for decoding a video according to the present invention may comprise: deriving a spatial 5 merge candidate for a current block, generating a merge candidate list for the current block based on the spatial merge candidate, obtaining motion information for the current block based on the merge candidate list, and performing motion compensation for the 10 current block based on the motion information. Herein, if the current block does not have a pre-defined shape or a size equal to or greater than a pre-defined size, the spatial merge candidate of the current block may be derived based on a block which have the pre-defined 15 shape or a size equal to or greater than the pre- defined size, the block including the current block. 61 , Claims:I/We Claim:

1. A method for decoding a video, the method comprising: 5 obtaining a residual coefficient of a current transform block; inverse-quantizing the residual coefficient; determining a transform type set of the current transform block; and 10 obtaining a residual sample of the current transform block by performing inverse-transform for the current transform block based on the transform type set, characterized in that: 15 in response to a case where a coding block including the current transform block is partitioned into two transform blocks, the transform type set of the current transform block is determined differently between when the coding block is 20 partitioned in a horizontal direction and when the coding block is partitioned in a vertical direction, and the coding block is obtained based on a tree- based block division including at least one of a 25 quad division or a binary division.

2. The method of claim 1, wherein the transform type set is constituted of a first transform type and a second transform type, wherein each of the first transform type and the second transform type is representative of DCT (Discrete Cosine Transform) 2, DST (Discrete Sine Transform) 7 or DCT 8, 5 wherein the first transform type is used for a horizontal transform for the current transform block, and wherein the second transform type is used for a vertical transform for the current transform 10 block.

3. The method of claim 1, wherein the transform type set of the current transform block is determined differently between when the current transform block 15 is one of the two transform blocks and when the current transform block is the other of the two transform blocks.

4. The method of claim 1, wherein the method 20 comprises: determining whether the transform type set of the current transform block is determined explicitly or implicitly, wherein when it is determined that the 25 transform type set of the current transform block is determined explicitly, the transform type set of the current transform block is determined based on index information explicitly signaled via a bitstream, the index information specifying one of a plurality of transform type sets, and wherein when it is determined that the transform type set of the current transform block is determined implicitly, the transform type set of 5 the current transform block is determined without parsing the index information from the bitstream.

5. The method of claim 4, wherein the determination of whether the transform type set of the current 10 transform block is determined explicitly or implicitly is based on a comparison between the size of the current transform block and a threshold size.

6. A method for encoding a video, the method 15 comprising: obtaining a residual sample of a current transform block; determining a transform type set of the current transform block; 20 obtaining a transform coefficient of the current transform block by performing transform for the current transform block based on the transform type set; and obtaining a residual coefficient by quantizing 25 the transform coefficient, characterized in that: in response to a case where a coding block including the current transform block is partitioned into two transform blocks, the transform type set of the current transform block is determined differently between when the coding block is partitioned in a horizontal direction and when the coding block is partitioned in a vertical direction, 5 and the coding block is obtained based on a tree- based block division including at least one of a quad division or a binary division. 10 7. A method of storing or transmitting compressed video data generated by an encoding method of claim

6. 8. A device for transmitting compressed video data, 15 comprising: a processor configured to obtain the compressed video data; and a transmitter configured to transmit the compressed video data, 20 wherein obtaining the compressed video data comprises: obtaining a residual sample of a current transform block; determining a transform type set of the current 25 transform block; obtaining a transform coefficient of the current transform block by performing transform for the current transform block based on the transform type set; and obtaining a residual coefficient by quantizing the transform coefficient, characterized in that: in response to a case where a coding block 5 including the current transform block is partitioned into two transform blocks, the transform type set of the current transform block is determined differently between when the coding block is partitioned in a horizontal direction and when the 10 coding block is partitioned in a vertical direction, and the coding block is obtained based on a tree- based block division including at least one of a quad division or a binary division.

Description:Technical Field
5 [0001] The present invention relates to a method
and an apparatus for processing video signal.
Background Art
[0002] Recently, demands for high-resolution and
10 high-quality images such as high definition (HD)
images and ultra-high definition (UHD) images have
increased in various application fields. However,
higher resolution and quality image data has
increasing amounts of data in comparison with
15 conventional image data. Therefore, when transmitting
image data by using a medium such as conventional
wired and wireless broadband networks, or when storing
image data by using a conventional storage medium,
costs of transmitting and storing increase. In order
20 to solve these problems occurring with an increase in
resolution and quality of image data, high-efficiency
image encoding/decoding techniques may be utilized.
[0003] Image compression technology includes
various techniques, including: an inter-prediction
25 technique of predicting a pixel value included in a
current picture from a previous or subsequent picture
of the current picture; an intra-prediction technique
of predicting a pixel value included in a current
picture by using pixel information in the current
30 picture; an entropy encoding technique of assigning a
short code to a value with a high appearance frequency
2
This is a Divisional Application of Indian Application
202118025749 Dated 09 June 2021
and assigning a long code to a value with a low
appearance frequency; etc. Image data may be
effectively compressed by using such image compression
technology, and may be transmitted or stored.
5 [0004] In the meantime, with demands for high-
resolution images, demands for stereographic image
content, which is a new image service, have also
increased. A video compression technique for
effectively providing stereographic image content with
10 high resolution and ultra-high resolution is being
discussed.
Disclosure
Technical Problem
15 [0005] An object of the present invention is to
provide a method and an apparatus for efficiently
performing a transform /inverse transform in
encoding/decoding a video signal.
[0006] An object of the present invention is to
20 provide a method and an apparatus for adaptively
determining a transform type of a current block among
a plurality of transform type candidates in
encoding/decoding a video signal.
[0007] An object of the present invention is to
25 provide a method and an apparatus for determining
transform types of a horizontal transform and a
vertical transform separately in encoding/decoding a
video signal.
[0008] The technical objects to be achieved by the
30 present invention are not limited to the above-
mentioned technical problems. And, other technical
3
problems that are not mentioned will be apparently
understood to those skilled in the art from the
following description.
5 Technical Solution
[0009] A method and an apparatus for decoding a
video signal according to the present invention may
obtain a transform coefficient of a current block,
inverse quantize the transform coefficient, determine
10 a transform set for the current block, determine one
of a plurality of transform type candidates as a
transform type of the current block, and inverse
transform the inverse quantized transform coefficient
based on the determined transform type.
15 [0010] A method and an apparatus for encoding a
video signal according to the present invention may
obtain a transform coefficient of a current block,
inverse quantize the transform coefficient, determine
a transform set for the current block, determine one
20 of a plurality of transform type candidates as a
transform type of the current block, and inverse
transform the inverse quantized transform coefficient
based on the determined transform type.
[0011] In the method and the apparatus for
25 encoding/decoding a video signal according to the
present invention, the transform set of the current
block may be determined based on index information
indicating at least one among a plurality of transform
sets.
30 [0012] In the method and the apparatus for
encoding/decoding a video signal according to the
4
present invention, at least one of a type or a number
of a transform type candidate for each of the
plurality of transform set may be different.
[0013] In the method and the apparatus for
5 encoding/decoding a video signal according to the
present invention, at least one of a type or a number
of a transform type candidate included in the
transform set may be determined differently according
to whether a transform skip is allowed or not.
10 [0014] In the method and the apparatus for
encoding/decoding a video signal according to the
present invention, the inverse transform may comprise
a horizontal transform and a vertical transform and a
transform set for the horizontal transform and a
15 transform set for the vertical transform may be
determined independently.
[0015] In the method and the apparatus for
encoding/decoding a video signal according to the
present invention, the transform set for the
20 horizontal transform and the transform set for the
vertical transform may be determined according to an
intra prediction mode of the current block.
[0016] In the method and the apparatus for
encoding/decoding a video signal according to the
25 present invention, the transform type of the current
block may be adaptively determined based on at least
one of a size, a shape or a number of samples of the
current block.
[0017] The features briefly summarized above for
30 the present invention are only illustrative aspects of
the detailed description of the invention that follows,
5
but do not limit the scope of the invention.
Advantageous Effects
[0018] According to the present invention, a
5 transform/inverse transform for an encoding/decoding
target block can be performed efficiently.
[0019] According to the present invention, a
transform type of a current block can be determined
adaptively among a plurality of transform type
10 candidates.
[0020] According to the present invention,
transform types of a horizontal transform and a
vertical transform can be determined separately.
[0021] The effects obtainable by the present
15 invention are not limited to the above-mentioned
effects, and other effects not mentioned can be
clearly understood by those skilled in the art from
the description below.
20 Description of Drawings
[0022] FIG. 1 is a block diagram illustrating a
device for encoding a video according to an embodiment
of the present invention.
[0023] FIG. 2 is a block diagram illustrating a
25 device for decoding a video according to an embodiment
of the present invention.
[0024] FIG. 3 is a diagram illustrating an example
of hierarchically partitioning a coding block based on
a tree structure according to an embodiment of the
30 present invention.
[0025] FIG. 4 is a diagram illustrating a
partition type in which binary tree-based partitioning
6
is allowed according to an embodiment of the present
invention.
[0026] FIG. 5 is a diagram illustrating an example
in which only a binary tree-based partition of a pre-
5 determined type is allowed according to an embodiment
of the present invention.
[0027] FIG. 6 is a diagram for explaining an
example in which information related to the allowable
number of binary tree partitioning is encoded/decoded,
10 according to an embodiment to which the present
invention is applied.
[0028] FIG. 7 is a diagram illustrating a
partition mode applicable to a coding block according
to an embodiment of the present invention.
15 [0029] FIG. 8 is a flowchart illustrating
processes of obtaining a residual sample according to
an embodiment of the present invention.
[0030] FIG. 9 is a diagram illustrating, for 33
intra prediction modes, whether a vertical transform
20 and a horizontal transform use the same transform set.
Mode for Invention
[0031] A variety of modifications may be made to
the present invention and there are various
25 embodiments of the present invention, examples of
which will now be provided with reference to drawings
and described in detail. However, the present
invention is not limited thereto, and the exemplary
embodiments can be construed as including all
30 modifications, equivalents, or substitutes in a
technical concept and a technical scope of the present
invention. The similar reference numerals refer to
7
the similar element in described the drawings.
[0032] Terms used in the specification, ‘first’,
‘second’, etc. can be used to describe various
components, but the components are not to be construed
5 as being limited to the terms. The terms are only
used to differentiate one component from other
components. For example, the ‘first’ component may be
named the ‘second’ component without departing from
the scope of the present invention, and the ‘second’
10 component may also be similarly named the ‘first’
component. The term ‘and/or’ includes a combination
of a plurality of items or any one of a plurality of
terms.
[0033] It will be understood that when an element
15 is simply referred to as being ‘connected to’ or
‘coupled to’ another element without being ‘directly
connected to’ or ‘directly coupled to’ another element
in the present description, it may be ‘directly
connected to’ or ‘directly coupled to’ another element
20 or be connected to or coupled to another element,
having the other element intervening therebetween. In
contrast, it should be understood that when an element
is referred to as being “directly coupled” or
“directly connected” to another element, there are no
25 intervening elements present.
[0034] The terms used in the present specification
are merely used to describe particular embodiments,
and are not intended to limit the present invention.
An expression used in the singular encompasses the
30 expression of the plural, unless it has a clearly
different meaning in the context. In the present
8
specification, it is to be understood that terms such
as “including”, “having”, etc. are intended to
indicate the existence of the features, numbers,
steps, actions, elements, parts, or combinations
5 thereof disclosed in the specification, and are not
intended to preclude the possibility that one or more
other features, numbers, steps, actions, elements,
parts, or combinations thereof may exist or may be
added.
10 [0035] Hereinafter, preferred embodiments of the
present invention will be described in detail with
reference to the accompanying drawings. Hereinafter,
the same constituent elements in the drawings are
denoted by the same reference numerals, and a repeated
15 description of the same elements will be omitted.
[0036] FIG. 1 is a block diagram illustrating a
device for encoding a video according to an embodiment
of the present invention.
[0037] Referring to FIG. 1, the device 100 for
20 encoding a video may include: a picture partitioning
module 110, prediction modules 120 and 125, a
transform module 130, a quantization module 135, a
rearrangement module 160, an entropy encoding module
165, an inverse quantization module 140, an inverse
25 transform module 145, a filter module 150, and a
memory 155.
[0038] The constitutional parts shown in FIG. 1
are independently shown so as to represent
characteristic functions different from each other in
30 the device for encoding a video. Thus, it does not
mean that each constitutional part is constituted in a
9
constitutional unit of separated hardware or software.
In other words, each constitutional part includes each
of enumerated constitutional parts for convenience.
Thus, at least two constitutional parts of each
5 constitutional part may be combined to form one
constitutional part or one constitutional part may be
divided into a plurality of constitutional parts to
perform each function. The embodiment where each
constitutional part is combined and the embodiment
10 where one constitutional part is divided are also
included in the scope of the present invention, if not
departing from the essence of the present invention.
[0039] Also, some of constituents may not be
indispensable constituents performing essential
15 functions of the present invention but be selective
constituents improving only performance thereof. The
present invention may be implemented by including only
the indispensable constitutional parts for
implementing the essence of the present invention
20 except the constituents used in improving performance.
The structure including only the indispensable
constituents except the selective constituents used in
improving only performance is also included in the
scope of the present invention.
25 [0040] The picture partitioning module 110 may
partition an input picture into one or more processing
units. Here, the processing unit may be a prediction
unit (PU), a transform unit (TU), or a coding unit
(CU). The picture partitioning module 110 may
30 partition one picture into combinations of multiple
coding units, prediction units, and transform units,
10
and may encode a picture by selecting one combination
of coding units, prediction units, and transform units
with a predetermined criterion (e.g., cost function).
[0041] For example, one picture may be partitioned
5 into multiple coding units. A recursive tree
structure, such as a quad tree structure, may be used
to partition a picture into coding units. A coding
unit which is partitioned into other coding units with
one picture or a largest coding unit as a root may be
10 partitioned with child nodes corresponding to the
number of partitioned coding units. A coding unit
which is no longer partitioned by a predetermined
limitation serves as a leaf node. That is, when it is
assumed that only square partitioning is possible for
15 one coding unit, one coding unit may be partitioned
into four other coding units at most.
[0042] Hereinafter, in the embodiment of the
present invention, the coding unit may mean a unit
performing encoding, or a unit performing decoding.
20 [0043] A prediction unit may be one of partitions
partitioned into a square or a rectangular shape
having the same size in a single coding unit, or a
prediction unit may be one of partitions partitioned
so as to have a different shape / size in a single
25 coding unit.
[0044] When a prediction unit subjected to intra
prediction is generated based on a coding unit and the
coding unit is not the smallest coding unit, intra
prediction may be performed without partitioning the
30 coding unit into multiple prediction units NxN.
[0045] The prediction modules 120 and 125 may
11
include an inter prediction module 120 performing
inter prediction and an intra prediction module 125
performing intra prediction. Whether to perform inter
prediction or intra prediction for the prediction unit
5 may be determined, and detailed information (e.g., an
intra prediction mode, a motion vector, a reference
picture, etc.) according to each prediction method may
be determined. Here, the processing unit subjected to
prediction may be different from the processing unit
10 for which the prediction method and detailed content
is determined. For example, the prediction method,
the prediction mode, etc. may be determined by the
prediction unit, and prediction may be performed by
the transform unit. A residual value (residual block)
15 between the generated prediction block and an original
block may be input to the transform module 130. Also,
prediction mode information, motion vector
information, etc. used for prediction may be encoded
with the residual value by the entropy encoding module
20 165 and may be transmitted to a device for decoding a
video. When a particular encoding mode is used, it is
possible to transmit to a device for decoding video by
encoding the original block as it is without
generating the prediction block through the prediction
25 modules 120 and 125.
[0046] The inter prediction module 120 may predict
the prediction unit based on information of at least
one of a previous picture or a subsequent picture of
the current picture, or may predict the prediction
30 unit based on information of some encoded regions in
the current picture, in some cases. The inter
12
prediction module 120 may include a reference picture
interpolation module, a motion prediction module, and
a motion compensation module.
[0047] The reference picture interpolation module
5 may receive reference picture information from the
memory 155 and may generate pixel information of an
integer pixel or less then the integer pixel from the
reference picture. In the case of luma pixels, an 8-
tap DCT-based interpolation filter having different
10 filter coefficients may be used to generate pixel
information of an integer pixel or less than an
integer pixel in a unit of a 1/4 pixel. In the case
of chroma signals, a 4-tap DCT-based interpolation
filter having different filter coefficient may be used
15 to generate pixel information of an integer pixel or
less than an integer pixel in a unit of a 1/8 pixel.
[0048] The motion prediction module may perform
motion prediction based on the reference picture
interpolated by the reference picture interpolation
20 module. As methods for calculating a motion vector,
various methods, such as a full search-based block
matching algorithm (FBMA), a three step search (TSS),
a new three-step search algorithm (NTS), etc., may be
used. The motion vector may have a motion vector
25 value in a unit of a 1/2 pixel or a 1/4 pixel based on
an interpolated pixel. The motion prediction module
may predict a current prediction unit by changing the
motion prediction method. As motion prediction
methods, various methods, such as a skip method, a
30 merge method, an AMVP (Advanced Motion Vector
Prediction) method, an intra block copy method, etc.,
13
may be used.
[0049] The intra prediction module 125 may
generate a prediction unit based on reference pixel
information neighboring to a current block which is
5 pixel information in the current picture. When the
neighboring block of the current prediction unit is a
block subjected to inter prediction and thus a
reference pixel is a pixel subjected to inter
prediction, the reference pixel included in the block
10 subjected to inter prediction may be replaced with
reference pixel information of a neighboring block
subjected to intra prediction. That is, when a
reference pixel is not available, at least one
reference pixel of available reference pixels may be
15 used instead of unavailable reference pixel
information.
[0050] Prediction modes in intra prediction may
include a directional prediction mode using reference
pixel information depending on a prediction direction
20 and a non-directional prediction mode not using
directional information in performing prediction. A
mode for predicting luma information may be different
from a mode for predicting chroma information, and in
order to predict the chroma information, intra
25 prediction mode information used to predict luma
information or predicted luma signal information may
be utilized.
[0051] In performing intra prediction, when the
size of the prediction unit is the same as the size of
30 the transform unit, intra prediction may be performed
on the prediction unit based on pixels positioned at
14
the left, the top left, and the top of the prediction
unit. However, in performing intra prediction, when
the size of the prediction unit is different from the
size of the transform unit, intra prediction may be
5 performed using a reference pixel based on the
transform unit. Also, intra prediction using NxN
partitioning may be used for only the smallest coding
unit.
[0052] In the intra prediction method, a
10 prediction block may be generated after applying an
AIS (Adaptive Intra Smoothing) filter to a reference
pixel depending on the prediction modes. The type of
the AIS filter applied to the reference pixel may
vary. In order to perform the intra prediction
15 method, an intra prediction mode of the current
prediction unit may be predicted from the intra
prediction mode of the prediction unit neighboring to
the current prediction unit. In prediction of the
prediction mode of the current prediction unit by
20 using mode information predicted from the neighboring
prediction unit, when the intra prediction mode of the
current prediction unit is the same as the intra
prediction mode of the neighboring prediction unit,
information indicating that the prediction modes of
25 the current prediction unit and the neighboring
prediction unit are equal to each other may be
transmitted using predetermined flag information.
When the prediction mode of the current prediction
unit is different from the prediction mode of the
30 neighboring prediction unit, entropy encoding may be
performed to encode prediction mode information of the
15
current block.
[0053] Also, a residual block including
information on a residual value which is a different
between the prediction unit subjected to prediction
5 and the original block of the prediction unit may be
generated based on prediction units generated by the
prediction modules 120 and 125. The generated
residual block may be input to the transform module
130.
10 [0054] The transform module 130 may transform the
residual block including the information on the
residual value between the original block and the
prediction unit generated by the prediction modules
120 and 125 by using a transform method, such as
15 discrete cosine transform (DCT), discrete sine
transform (DST), and KLT. Whether to apply DCT, DST,
or KLT in order to transform the residual block may be
determined based on intra prediction mode information
of the prediction unit used to generate the residual
20 block.
[0055] The quantization module 135 may quantize
values transformed to a frequency domain by the
transform module 130. Quantization coefficients may
vary depending on the block or importance of a
25 picture. The values calculated by the quantization
module 135 may be provided to the inverse quantization
module 140 and the rearrangement module 160.
[0056] The rearrangement module 160 may rearrange
coefficients of quantized residual values.
30 [0057] The rearrangement module 160 may change a
coefficient in the form of a two-dimensional block
16
into a coefficient in the form of a one-dimensional
vector through a coefficient scanning method. For
example, the rearrangement module 160 may scan from a
DC coefficient to a coefficient in a high frequency
5 domain using a zigzag scanning method so as to change
the coefficients to be in the form of one-dimensional
vectors. Depending on the size of the transform unit
and the intra prediction mode, vertical direction
scanning where coefficients in the form of two-
10 dimensional blocks are scanned in the column direction
or horizontal direction scanning where coefficients in
the form of two-dimensional blocks are scanned in the
row direction may be used instead of zigzag scanning.
That is, which scanning method among zigzag scanning,
15 vertical direction scanning, and horizontal direction
scanning is used may be determined depending on the
size of the transform unit and the intra prediction
mode.
[0058] The entropy encoding module 165 may perform
20 entropy encoding based on the values calculated by the
rearrangement module 160. Entropy encoding may use
various encoding methods, for example, exponential
Golomb coding, context-adaptive variable length coding
(CAVLC), and context-adaptive binary arithmetic coding
25 (CABAC).
[0059] The entropy encoding module 165 may encode
a variety of information, such as residual value
coefficient information and block type information of
the coding unit, prediction mode information,
30 partition unit information, prediction unit
information, transform unit information, motion vector
17
information, reference frame information, block
interpolation information, filtering information, etc.
from the rearrangement module 160 and the prediction
modules 120 and 125.
5 [0060] The entropy encoding module 165 may entropy
encode the coefficients of the coding unit input from
the rearrangement module 160.
[0061] The inverse quantization module 140 may
inversely quantize the values quantized by the
10 quantization module 135 and the inverse transform
module 145 may inversely transform the values
transformed by the transform module 130. The residual
value generated by the inverse quantization module 140
and the inverse transform module 145 may be combined
15 with the prediction unit predicted by a motion
estimation module, a motion compensation module, and
the intra prediction module of the prediction modules
120 and 125 such that a reconstructed block can be
generated.
20 [0062] The filter module 150 may include at least
one of a deblocking filter, an offset correction unit,
and an adaptive loop filter (ALF).
[0063] The deblocking filter may remove block
distortion that occurs due to boundaries between the
25 blocks in the reconstructed picture. In order to
determine whether to perform deblocking, the pixels
included in several rows or columns in the block may
be a basis of determining whether to apply the
deblocking filter to the current block. When the
30 deblocking filter is applied to the block, a strong
filter or a weak filter may be applied depending on
18
required deblocking filtering strength. Also, in
applying the deblocking filter, horizontal direction
filtering and vertical direction filtering may be
processed in parallel.
5 [0064] The offset correction module may correct
offset with the original picture in a unit of a pixel
in the picture subjected to deblocking. In order to
perform the offset correction on a particular picture,
it is possible to use a method of applying offset in
10 consideration of edge information of each pixel or a
method of partitioning pixels of a picture into the
predetermined number of regions, determining a region
to be subjected to perform offset, and applying the
offset to the determined region.
15 [0065] Adaptive loop filtering (ALF) may be
performed based on the value obtained by comparing the
filtered reconstructed picture and the original
picture. The pixels included in the picture may be
divided into predetermined groups, a filter to be
20 applied to each of the groups may be determined, and
filtering may be individually performed for each
group. Information on whether to apply ALF and a luma
signal may be transmitted by coding units (CU). The
shape and filter coefficient of a filter for ALF may
25 vary depending on each block. Also, the filter for
ALF in the same shape (fixed shape) may be applied
regardless of characteristics of the application
target block.
[0066] The memory 155 may store the reconstructed
30 block or picture calculated through the filter module
150. The stored reconstructed block or picture may be
19
provided to the prediction modules 120 and 125 in
performing inter prediction.
[0067] FIG. 2 is a block diagram illustrating a
device for decoding a video according to an embodiment
5 of the present invention.
[0068] Referring to FIG. 2, the device 200 for
decoding a video may include: an entropy decoding
module 210, a rearrangement module 215, an inverse
quantization module 220, an inverse transform module
10 225, prediction modules 230 and 235, a filter module
240, and a memory 245.
[0069] When a video bitstream is input from the
device for encoding a video, the input bitstream may
be decoded according to an inverse process of the
15 device for encoding a video.
[0070] The entropy decoding module 210 may perform
entropy decoding according to an inverse process of
entropy encoding by the entropy encoding module of the
device for encoding a video. For example,
20 corresponding to the methods performed by the device
for encoding a video, various methods, such as
exponential Golomb coding, context-adaptive variable
length coding (CAVLC), and context-adaptive binary
arithmetic coding (CABAC) may be applied.
25 [0071] The entropy decoding module 210 may decode
information on intra prediction and inter prediction
performed by the device for encoding a video.
[0072] The rearrangement module 215 may perform
rearrangement on the bitstream entropy decoded by the
30 entropy decoding module 210 based on the rearrangement
method used in the device for encoding a video. The
20
rearrangement module may reconstruct and rearrange the
coefficients in the form of one-dimensional vectors to
the coefficient in the form of two-dimensional blocks.
The rearrangement module 215 may receive information
5 related to coefficient scanning performed in the
device for encoding a video and may perform
rearrangement via a method of inversely scanning the
coefficients based on the scanning order performed in
the device for encoding a video.
10 [0073] The inverse quantization module 220 may
perform inverse quantization based on a quantization
parameter received from the device for encoding a
video and the rearranged coefficients of the block.
[0074] The inverse transform module 225 may
15 perform the inverse transform, i.e., inverse DCT,
inverse DST, and inverse KLT, which is the inverse
process of transform, i.e., DCT, DST, and KLT,
performed by the transform module on the quantization
result by the device for encoding a video. Inverse
20 transform may be performed based on a transfer unit
determined by the device for encoding a video. The
inverse transform module 225 of the device for
decoding a video may selectively perform transform
schemes (e.g., DCT, DST, and KLT) depending on
25 multiple pieces of information, such as the prediction
method, the size of the current block, the prediction
direction, etc.
[0075] The prediction modules 230 and 235 may
generate a prediction block based on information on
30 prediction block generation received from the entropy
decoding module 210 and previously decoded block or
21
picture information received from the memory 245.
[0076] As described above, like the operation of
the device for encoding a video, in performing intra
prediction, when the size of the prediction unit is
5 the same as the size of the transform unit, intra
prediction may be performed on the prediction unit
based on the pixels positioned at the left, the top
left, and the top of the prediction unit. In
performing intra prediction, when the size of the
10 prediction unit is different from the size of the
transform unit, intra prediction may be performed
using a reference pixel based on the transform unit.
Also, intra prediction using NxN partitioning may be
used for only the smallest coding unit.
15 [0077] The prediction modules 230 and 235 may
include a prediction unit determination module, an
inter prediction module, and an intra prediction
module. The prediction unit determination module may
receive a variety of information, such as prediction
20 unit information, prediction mode information of an
intra prediction method, information on motion
prediction of an inter prediction method, etc. from
the entropy decoding module 210, may divide a current
coding unit into prediction units, and may determine
25 whether inter prediction or intra prediction is
performed on the prediction unit. By using
information required in inter prediction of the
current prediction unit received from the device for
encoding a video, the inter prediction module 230 may
30 perform inter prediction on the current prediction
unit based on information of at least one of a
22
previous picture or a subsequent picture of the
current picture including the current prediction unit.
Alternatively, inter prediction may be performed based
on information of some pre-reconstructed regions in
5 the current picture including the current prediction
unit.
[0078] In order to perform inter prediction, it
may be determined for the coding unit which of a skip
mode, a merge mode, an AMVP mode, and an inter block
10 copy mode is used as the motion prediction method of
the prediction unit included in the coding unit.
[0079] The intra prediction module 235 may
generate a prediction block based on pixel information
in the current picture. When the prediction unit is a
15 prediction unit subjected to intra prediction, intra
prediction may be performed based on intra prediction
mode information of the prediction unit received from
the device for encoding a video. The intra prediction
module 235 may include an adaptive intra smoothing
20 (AIS) filter, a reference pixel interpolation module,
and a DC filter. The AIS filter performs filtering on
the reference pixel of the current block, and whether
to apply the filter may be determined depending on the
prediction mode of the current prediction unit. AIS
25 filtering may be performed on the reference pixel of
the current block by using the prediction mode of the
prediction unit and AIS filter information received
from the device for encoding a video. When the
prediction mode of the current block is a mode where
30 AIS filtering is not performed, the AIS filter may not
be applied.
23
[0080] When the prediction mode of the prediction
unit is a prediction mode in which intra prediction is
performed based on the pixel value obtained by
interpolating the reference pixel, the reference pixel
5 interpolation module may interpolate the reference
pixel to generate the reference pixel of an integer
pixel or less than an integer pixel. When the
prediction mode of the current prediction unit is a
prediction mode in which a prediction block is
10 generated without interpolation the reference pixel,
the reference pixel may not be interpolated. The DC
filter may generate a prediction block through
filtering when the prediction mode of the current
block is a DC mode.
15 [0081] The reconstructed block or picture may be
provided to the filter module 240. The filter module
240 may include the deblocking filter, the offset
correction module, and the ALF.
[0082] Information on whether or not the
20 deblocking filter is applied to the corresponding
block or picture and information on which of a strong
filter and a weak filter is applied when the
deblocking filter is applied may be received from the
device for encoding a video. The deblocking filter of
25 the device for decoding a video may receive
information on the deblocking filter from the device
for encoding a video, and may perform deblocking
filtering on the corresponding block.
[0083] The offset correction module may perform
30 offset correction on the reconstructed picture based
on the type of offset correction and offset value
24
information applied to a picture in performing
encoding.
[0084] The ALF may be applied to the coding unit
based on information on whether to apply the ALF, ALF
5 coefficient information, etc. received from the device
for encoding a video. The ALF information may be
provided as being included in a particular parameter
set.
[0085] The memory 245 may store the reconstructed
10 picture or block for use as a reference picture or
block, and may provide the reconstructed picture to an
output module.
[0086] As described above, in the embodiment of
the present invention, for convenience of explanation,
15 the coding unit is used as a term representing a unit
for encoding, but the coding unit may serve as a unit
performing decoding as well as encoding.
[0087] In addition, a current block may represent
a target block to be encoded/decoded. And, the current
20 block may represent a coding tree block (or a coding
tree unit), a coding block (or a coding unit), a
transform block (or a transform unit), a prediction
block (or a prediction unit), or the like depending on
an encoding/decoding step.
25 [0088] A picture may be encoded/decoded by divided
into base blocks having a square shape or a non-square
shape. At this time, the base block may be referred to
as a coding tree unit. The coding tree unit may be
defined as a coding unit of the largest size allowed
30 within a sequence or a slice. Information regarding
whether the coding tree unit has a square shape or has
25
a non-square shape or information regarding a size of
the coding tree unit may be signaled through a
sequence parameter set, a picture parameter set, or a
slice header. The coding tree unit may be divided
5 into smaller size partitions. At this time, if it is
assumed that a depth of a partition generated by
dividing the coding tree unit is 1, a depth of a
partition generated by dividing the partition having
depth 1 may be defined as 2. That is, a partition
10 generated by dividing a partition having a depth k in
the coding tree unit may be defined as having a depth
k+1.
[0089] A partition of arbitrary size generated by
dividing a coding tree unit may be defined as a coding
15 unit. The coding unit may be recursively divided or
divided into base units for performing prediction,
quantization, transform, or in-loop filtering, and the
like. For example, a partition of arbitrary size
generated by dividing the coding unit may be defined
20 as a coding unit, or may be defined as a transform
unit or a prediction unit, which is a base unit for
performing prediction, quantization, transform or in-
loop filtering and the like.
[0090] Partitioning of a coding tree unit or a
25 coding unit may be performed based on at least one of
a vertical line and a horizontal line. In addition,
the number of vertical lines or horizontal lines
partitioning the coding tree unit or the coding unit
may be at least one or more. For example, the coding
30 tree unit or the coding unit may be divided into two
partitions using one vertical line or one horizontal
26
line, or the coding tree unit or the coding unit may
be divided into three partitions using two vertical
lines or two horizontal lines. Alternatively, the
coding tree unit or the coding unit may be partitioned
5 into four partitions having a length and a width of
1/2 by using one vertical line and one horizontal
line.
[0091] When a coding tree unit or a coding unit is
divided into a plurality of partitions using at least
10 one vertical line or at least one horizontal line, the
partitions may have a uniform size or a different
size. Alternatively, any one partition may have a
different size from the remaining partitions.
[0092] In the embodiments described below, it is
15 assumed that a coding tree unit or a coding unit is
divided into a quad tree structure or a binary tree
structure. However, it is also possible to divide a
coding tree unit or a coding unit using a larger
number of vertical lines or a larger number of
20 horizontal lines.
[0093] FIG. 3 is a diagram illustrating an example
of hierarchically partitioning a coding block based on
a tree structure according to an embodiment of the
present invention.
25 [0094] An input video signal is decoded in
predetermined block units. Such a default unit for
decoding the input video signal is a coding block.
The coding block may be a unit performing intra/inter
prediction, transform, and quantization. In addition,
30 a prediction mode (e.g., intra prediction mode or
inter prediction mode) is determined in a unit of a
27
coding block, and the prediction blocks included in
the coding block may share the determined prediction
mode. The coding block may be a square or non-square
block having an arbitrary size in a range of 8x8 to
5 64x64, or may be a square or non-square block having a
size of 128x128, 256x256, or more.
[0095] Specifically, the coding block may be
hierarchically partitioned based on at least one of a
quad tree and a binary tree. Here, quad tree-based
10 partitioning may mean that a 2Nx2N coding block is
partitioned into four NxN coding blocks, and binary
tree-based partitioning may mean that one coding block
is partitioned into two coding blocks. Even if the
binary tree-based partitioning is performed, a square-
15 shaped coding block may exist in the lower depth.
[0096] Binary tree-based partitioning may be
symmetrically or asymmetrically performed. The coding
block partitioned based on the binary tree may be a
square block or a non-square block, such as a
20 rectangular shape. For example, a partition type in
which the binary tree-based partitioning is allowed
may comprise at least one of a symmetric type of 2NxN
(horizontal directional non-square coding unit) or
Nx2N (vertical direction non-square coding unit),
25 asymmetric type of nLx2N, nRx2N, 2NxnU, or 2NxnD.
[0097] Binary tree-based partitioning may be
limitedly allowed to one of a symmetric or an
asymmetric type partition. In this case, constructing
the coding tree unit with square blocks may correspond
30 to quad tree CU partitioning, and constructing the
coding tree unit with symmetric non-square blocks may
28
correspond to binary tree partitioning. Constructing
the coding tree unit with square blocks and symmetric
non-square blocks may correspond to quad and binary
tree CU partitioning.
5 [0098] Binary tree-based partitioning may be
performed on a coding block where quad tree-based
partitioning is no longer performed. Quad tree-based
partitioning may no longer be performed on the coding
block partitioned based on the binary tree.
10 [0099] Furthermore, partitioning of a lower depth
may be determined depending on a partition type of an
upper depth. For example, if binary tree-based
partitioning is allowed in two or more depths, only
the same type as the binary tree partitioning of the
15 upper depth may be allowed in the lower depth. For
example, if the binary tree-based partitioning in the
upper depth is performed with 2NxN type, the binary
tree-based partitioning in the lower depth is also
performed with 2NxN type. Alternatively, if the binary
20 tree-based partitioning in the upper depth is
performed with Nx2N type, the binary tree-based
partitioning in the lower depth is also performed with
Nx2N type.
[00100] On the contrary, it is also possible to
25 allow, in a lower depth, only a type different from a
binary tree partitioning type of an upper depth.
[00101] It may be possible to limit only a specific
type of binary tree based partitioning to be used for
sequence, slice, coding tree unit, or coding unit. As
30 an example, only 2NxN type or Nx2N type of binary
tree-based partitioning may be allowed for the coding
29
tree unit. An available partition type may be
predefined in an encoder or a decoder. Or information
on available partition type or on unavailable
partition type on may be encoded and then signaled
5 through a bitstream.
[00102] FIG. 5 is a diagram illustrating an example
in which only a specific type of binary tree-based
partitioning is allowed. FIG. 5A shows an example in
which only Nx2N type of binary tree-based partitioning
10 is allowed, and FIG. 5B shows an example in which only
2NxN type of binary tree-based partitioning is
allowed. In order to implement adaptive partitioning
based on the quad tree or binary tree, information
indicating quad tree-based partitioning, information
15 on the size/depth of the coding block that quad tree-
based partitioning is allowed, information indicating
binary tree-based partitioning, information on the
size/depth of the coding block that binary tree-based
partitioning is allowed, information on the size/depth
20 of the coding block that binary tree-based
partitioning is not allowed, information on whether
binary tree-based partitioning is performed in a
vertical direction or a horizontal direction, etc. may
be used.
25 [00103] In addition, information on the number of
times a binary tree partitioning is allowed, a depth
at which the binary tree partitioning is allowed, or
the number of the depths at which the binary tree
partitioning is allowed may be obtained for a coding
30 tree unit or a specific coding unit. The information
may be encoded in a unit of a coding tree unit or a
30
coding unit, and may be transmitted to a decoder
through a bitstream.
[00104] For example, a syntax
'max_binary_depth_idx_minus1' indicating a maximum
5 depth at which binary tree partitioning is allowed may
be encoded / decoded through a bitstream. In this
case, max_binary_depth_idx_minus1 + 1 may indicate the
maximum depth at which the binary tree partitioning is
allowed.
10 [00105] Referring to the example shown in FIG. 6,
in FIG. 6, the binary tree partitioning has been
performed for a coding unit having a depth of 2 and a
coding unit having a depth of 3. Accordingly, at least
one of information indicating the number of times the
15 binary tree partitioning in the coding tree unit has
been performed (i.e., 2 times), information indicating
the maximum depth which the binary tree partitioning
has been allowed in the coding tree unit (i.e., depth
3), or the number of depths in which the binary tree
20 partitioning has been performed in the coding tree
unit (i.e., 2 (depth 2 and depth 3)) may be encoded /
decoded through a bitstream.
[00106] As another example, at least one of
information on the number of times the binary tree
25 partitioning is permitted, the depth at which the
binary tree partitioning is allowed, or the number of
the depths at which the binary tree partitioning is
allowed may be obtained for each sequence or each
slice. For example, the information may be encoded in
30 a unit of a sequence, a picture, or a slice unit and
transmitted through a bitstream. Accordingly, at least
31
one of the number of the binary tree partitioning in a
first slice, the maximum depth in which the binary
tree partitioning is allowed in the first slice, or
the number of depths in which the binary tree
5 partitioning is performed in the first slice may be
difference from a second slice. For example, in the
first slice, binary tree partitioning may be permitted
for only one depth, while in the second slice, binary
tree partitioning may be permitted for two depths.
10 [00107] As another example, the number of times the
binary tree partitioning is permitted, the depth at
which the binary tree partitioning is allowed, or the
number of depths at which the binary tree partitioning
is allowed may be set differently according to a time
15 level identifier (TemporalID) of a slice or a picture.
Here, the temporal level identifier (TemporalID) is
used to identify each of a plurality of layers of
video having a scalability of at least one of view,
spatial, temporal or quality.
20 [00108] As shown in FIG. 3, the first coding block
300 with the partition depth (split depth) of k may be
partitioned into multiple second coding blocks based
on the quad tree. For example, the second coding
blocks 310 to 340 may be square blocks having the half
25 width and the half height of the first coding block,
and the partition depth of the second coding block may
be increased to k+1.
[00109] The second coding block 310 with the
partition depth of k+1 may be partitioned into
30 multiple third coding blocks with the partition depth
of k+2. Partitioning of the second coding block 310
32
may be performed by selectively using one of the quad
tree and the binary tree depending on a partitioning
method. Here, the partitioning method may be
determined based on at least one of the information
5 indicating quad tree-based partitioning and the
information indicating binary tree-based partitioning.
[00110] When the second coding block 310 is
partitioned based on the quad tree, the second coding
block 310 may be partitioned into four third coding
10 blocks 310a having the half width and the half height
of the second coding block, and the partition depth of
the third coding block 310a may be increased to k+2.
In contrast, when the second coding block 310 is
partitioned based on the binary tree, the second
15 coding block 310 may be partitioned into two third
coding blocks. Here, each of two third coding blocks
may be a non-square block having one of the half width
and the half height of the second coding block, and
the partition depth may be increased to k+2. The
20 second coding block may be determined as a non-square
block of a horizontal direction or a vertical
direction depending on a partitioning direction, and
the partitioning direction may be determined based on
the information on whether binary tree-based
25 partitioning is performed in a vertical direction or a
horizontal direction.
[00111] In the meantime, the second coding block
310 may be determined as a leaf coding block that is
no longer partitioned based on the quad tree or the
30 binary tree. In this case, the leaf coding block may
be used as a prediction block or a transform block.
33
[00112] Like partitioning of the second coding
block 310, the third coding block 310a may be
determined as a leaf coding block, or may be further
partitioned based on the quad tree or the binary tree.
5 [00113] In the meantime, the third coding block
310b partitioned based on the binary tree may be
further partitioned into coding blocks 310b-2 of a
vertical direction or coding blocks 310b-3 of a
horizontal direction based on the binary tree, and the
10 partition depth of the relevant coding blocks may be
increased to k+3. Alternatively, the third coding
block 310b may be determined as a leaf coding block
310b-1 that is no longer partitioned based on the
binary tree. In this case, the coding block 310b-1
15 may be used as a prediction block or a transform
block. However, the above partitioning process may be
limitedly performed based on at least one of the
information on the size/depth of the coding block that
quad tree-based partitioning is allowed, the
20 information on the size/depth of the coding block that
binary tree-based partitioning is allowed, and the
information on the size/depth of the coding block that
binary tree-based partitioning is not allowed.
[00114] A number of a candidate that represent a
25 size of a coding block may be limited to a
predetermined number, or a size of a coding block in a
predetermined unit may have a fixed value. As an
example, the size of the coding block in a sequence or
in a picture may be limited to have 256x256, 128x128,
30 or 32x32. Information indicating the size of the
coding block in the sequence or in the picture may be
34
signaled through a sequence header or a picture
header.
[00115] As a result of partitioning based on a quad
tree and a binary tree, a coding unit may be
5 represented as square or rectangular shape of an
arbitrary size.
[00116] A coding block is encoded using at least
one of a skip mode, intra prediction, inter
prediction, or a skip method. Once a coding block is
10 determined, a prediction block may be determined
through predictive partitioning of the coding block.
The predictive partitioning of the coding block may be
performed by a partition mode (Part_mode) indicating a
partition type of the coding block. A size or a shape
15 of the prediction block may be determined according to
the partition mode of the coding block. For example, a
size of a prediction block determined according to the
partition mode may be equal to or smaller than a size
of a coding block.
20 [00117] FIG. 7 is a diagram illustrating a
partition mode that may be applied to a coding block
when the coding block is encoded by inter prediction.
[00118] When a coding block is encoded by inter
prediction, one of 8 partitioning modes may be applied
25 to the coding block, as in the example shown in FIG.
4.
[00119] When a coding block is encoded by intra
prediction, a partition mode PART_2Nx2N or a partition
mode PART_NxN may be applied to the coding block.
30 [00120] PART_NxN may be applied when a coding block
has a minimum size. Here, the minimum size of the
35
coding block may be pre-defined in an encoder and a
decoder. Or, information regarding the minimum size of
the coding block may be signaled via a bitstream. For
example, the minimum size of the coding block may be
5 signaled through a slice header, so that the minimum
size of the coding block may be defined per slice.
[00121] In general, a prediction block may have a
size from 64×64 to 4×4. However, when a coding block
is encoded by inter prediction, it may be restricted
10 that the prediction block does not have a 4x4 size in
order to reduce memory bandwidth when performing
motion compensation.
[00122] FIG. 8 is a flowchart illustrating
processes of obtaining a residual sample according to
15 an embodiment of the present invention.
[00123] First, a residual coefficient of a current
block may be obtained S810. The decoder may obtain the
residual coefficient through a coefficient scanning
method. For example, the decoder may perform
20 coefficient scanning using a diagonal scan, a zigzag
scan, an up-right scan, a vertical scan, or a
horizontal scan, and thereby obtain residual
coefficients in a shape of a two-dimensional block.
[00124] Inverse quantization may be performed for
25 the residual coefficient of the current block S820.
[00125] It is possible to determine whether to skip
an inverse transform on the dequantized residual
coefficient of the current block S830. Specifically,
the decoder may determine whether to skip the inverse
30 transform on at least one of a horizontal direction or
a vertical direction of the current block. When it is
36
determined to apply the inverse transform on at least
one of the horizontal direction or the vertical
direction of the current block, a residual sample of
the current block may be obtained by inverse
5 transforming the dequantized residual coefficient of
the current block S840. Here, the inverse transform
may be performed using at least one of DCT, DST, and
KLT.
[00126] When the inverse transform is skipped in
10 both the horizontal direction and the vertical
direction of the current block, the inverse transform
is not performed in the horizontal direction and the
vertical direction of the current block. In this case,
the residual sample of the current block may be
15 obtained by scaling the dequantized residual
coefficient with a predetermined value S850.
[00127] Skipping the inverse transform on the
horizontal direction means that the inverse transform
is not performed on the horizontal direction but the
20 inverse transform is performed on the vertical
direction. At this time, scaling may be performed in
the horizontal direction.
[00128] Skipping the inverse transform on the
vertical direction means that the inverse transform is
25 not performed on the vertical direction but the
inverse transform is performed on the horizontal
direction. At this time, scaling may be performed in
the vertical direction.
[00129] It may be determined whether or not an
30 inverse transform skip technique may be used for the
current block depending on a partition type of the
37
current block. For example, if the current block is
generated through a binary tree-based partitioning,
the inverse transform skip scheme may be restricted
for the current block. Accordingly, when the current
5 block is generated through the binary tree-based
partitioning, the residual sample of the current block
may be obtained by inverse transforming the current
block. In addition, when the current block is
generated through binary tree-based partitioning,
10 encoding/decoding of information indicating whether or
not the inverse transform is skipped (e.g.,
transform_skip_flag) may be omitted.
[00130] Alternatively, when the current block is
generated through binary tree-based partitioning, it
15 is possible to limit the inverse transform skip scheme
to at least one of the horizontal direction or the
vertical direction. Here, the direction in which the
inverse transform skip scheme is limited may be
determined based on information decoded from the
20 bitstream, or may be adaptively determined based on at
least one of a size of the current block, a shape of
the current block, or an intra prediction mode of the
current block.
[00131] For example, when the current block is a
25 non-square block having a width greater than a height,
the inverse transform skip scheme may be allowed only
in the vertical direction and restricted in the
horizontal direction. That is, when the current block
is 2NxN, the inverse transform is performed in the
30 horizontal direction of the current block, and the
inverse transform may be selectively performed in the
38
vertical direction.
[00132] On the other hand, when the current block
is a non-square block having a height greater than a
width, the inverse transform skip scheme may be
5 allowed only in the horizontal direction and
restricted in the vertical direction. That is, when
the current block is Nx2N, the inverse transform is
performed in the vertical direction of the current
block, and the inverse transform may be selectively
10 performed in the horizontal direction.
[00133] In contrast to the above example, when the
current block is a non-square block having a width
greater than a height, the inverse transform skip
scheme may be allowed only in the horizontal
15 direction, and when the current block is a non-square
block having a height greater than a width, the
inverse transform skip scheme may be allowed only in
the vertical direction.
[00134] Information indicating whether or not to
20 skip the inverse transform with respect to the
horizontal direction or information indicating whether
to skip the inverse transformation with respect to the
vertical direction may be signaled through a
bitstream. For example, the information indicating
25 whether or not to skip the inverse transform on the
horizontal direction is a 1-bit flag,
'hor_transform_skip_flag', and information indicating
whether to skip the inverse transform on the vertical
direction is a 1-bit flag, 'ver_transform_skip_flag '.
30 The encoder may encode at least one of
'hor_transform_skip_flag' or 'ver_transform_skip_flag'
39
according to the shape of the current block. Further,
the decoder may determine whether or not the inverse
transform on the horizontal direction or on the
vertical direction is skipped by using at least one of
5 "hor_transform_skip_flag" or
"ver_transform_skip_flag".
[00135] It may be set to skip the inverse transform
for any one direction of the current block depending
on a partition type of the current block. For example,
10 if the current block is generated through a binary
tree-based partitioning, the inverse transform on the
horizontal direction or vertical direction may be
skipped. That is, if the current block is generated by
binary tree-based partitioning, it may be determined
15 that the inverse transform for the current block is
skipped on at least one of a horizontal direction or a
vertical direction without encoding/decoding
information (e.g., transform_skip_flag,
hor_transform_skip_flag, ver_transform_skip_flag)
20 indicating whether or not the inverse transform of the
current block is skipped.
[00136] If it is determined to apply the inverse
transform to the current block, a transform type may
be determined and the inverse transform may be
25 performed using the determined transform type. The
transform type of the current block (e.g., a transform
block or a coding block) may be determined based on at
least one of a size or an encoding mode of the current
block. Here, the encoding mode may indicate whether a
30 prediction block corresponding to the coding block or
the transform block is encoded in intra mode or inter
40
mode.
[00137] For example, the inverse transform for a
block of 4x4 encoded in the intra mode may be
performed by using DST (specifically, DST-VII), and
5 the inverse transform for a block other than the block
may be performed by using DCT (specifically, DCT-II).
[00138] DST-VII may be defined as matrix A4 of
Equation 1. The inverse transform of DST-VII may be
defined as A4T.
10 [00139] [Equation 1]
[00140] The DCT-II for a block of 8x8 may be
defined as matrix T8 of Equation 2. The inverse
transform of DCT-II may be defined as T8T.
15 [00141] [Equation 2]
41
[00142] A condition for selecting the transform
type may be set differently on a unit of a sequence, a
slice or a block. For example, in slice 0, DST is
5 applied to a transform block of 4x4 encoded in the
intra mode, whereas in slice 0, DST is applied to a
transform block of 8x8 or smaller encoded in the intra
mode.
[00143] As another example, the transform type of
10 the current block may be adaptively determined based
on at least one of an intra prediction mode of the
current block or the number of samples included in the
current block. At this time, the number of samples
used as a reference for selecting the transform type
15 may have a fixed value or may be determined through
information signaled via the bitstream. The
information may be signaled via a block level, a slice
header, or a picture parameter set.
[00144] For example, DST may be applied only when
20 the current block includes 16 or less samples and when
the current block is encoded in the intra mode, and
42
DCT may be applied in other cases. Specifically, DST
may be applied to a block of 4x4, 2x8 or 8x2 encoded
by the intra prediction, and DCT may be applied to a
block other than the block.
5 [00145] Alternatively, the transform type of the
current block may be determined from transform set
candidates included in a transform set. At this time,
different transform sets can be used in a unit of a
coding block or a transform block. Alternatively, a
10 plurality of transform blocks included in a
predetermined coding block may share the same
transform set. To determine the transform set, index
information for identifying the transform set may be
signaled in a unit of a coding block or a transform
15 block. Alternatively, the transform set of the current
block may be adaptively determined according to a
size, a shape, an encoding mode, an intra prediction
mode, the number of samples of the current block, or
the like.
20 [00146] The transform set may include a plurality
of transform type candidates that may be selectively
used according to the shape, the size, or the number
of samples of the transform block (or the coding
block). At this time, at least one of the number or
25 types of transform type candidates included in
transform sets may be different.
[00147] Table 1 is a chart depicting transform sets
including different transform type candidates.
[00148] [Table 1]
Transform set Index Transform
candidates 0
Transform
candidates 1
43
0 DST-VII DCT-II
1 DST-VII DST-I
2 DST-VII DCT-VIII
[00149] In Table 1, it is illustrated that the
number of transform type candidates included in the
transform set is two. It is also possible that the
transform set includes one, three, four or more
5 transform type candidates.
[00150] In addition, the number of transform type
candidates included in at least one of the transform
sets may be different from the number of transform
type candidates included in another transform set. The
10 number of maximum transform type candidates included
in the transform set may be signaled in a slice or a
sequence header.
[00151] The transform type of the current block may
be determined to be at least one of the transform type
15 candidates included in the transform set. At this
time, the transform type of the transform block may be
determined based on a size, an encoding mode, an intra
prediction mode, the number of samples of the
transform block or the coding block, or the like.
20 Here, the intra prediction mode of the transform block
may be the intra prediction mode of the prediction
block or the coding block corresponding to the
transform block.
[00152] For example, when transform set index 0 is
25 determined as the transform set of the current block,
if the current block is a 4×4 block encoded in the
intra mode, transform type candidate 0, i.e., DST-VII
is used, and if the current block does not satisfy the
44
above condition, transform type candidate 1, i.e. DCT-
II, is used.
[00153] Alternatively, when transform set index 2
is determined as the transform set of the current
5 block, if the current block is 4x4 or 8x8 block
encoded in the intra mode, transform type candidate 0,
i.e., DST-VII is applied, and if the current block
does not satisfy the above condition, transform type
candidate 1, i.e., DCT-VIII, is used.
10 [00154] According to a size of the coding block, a
condition for selecting the transform type candidate
of the transform block may be set differently. For
example, when the size of the coding block is smaller
than or equal to 32x32, transform type candidate 0 is
15 applied to a transform block of 4x4 encoded in the
intra mode, and transform type candidate 1 is applied
to a transform block which does not satisfy the above
conditions. On the other hand, when the size of the
coding block is larger than 32x32, transform type
20 candidate 0 is applied to a block of 4x4 or 8x8
encoded in the intra mode, and transform type
candidate 1 is applied to a transform block which does
not satisfy the above conditions.
[00155] The transform type candidate may include a
25 transform skip indicating that no transform is
performed. Depending on whether a transform skip is
allowed, at least one of types or the number of
transform type candidates included in the transform
set may be set differently. As an example, if the
30 transform_skip_enabled_flag indicating whether or not
to allow the transform skip in a picture is 1, a
45
transform set which further including the transform
skip as the transform type candidate may be used, as
shown in Table 2. On the other hand, if
transform_skip_enabled_flag is 0, a transform set
5 which does not include the transform skip as the
transform type candidate may be used, as shown in
Table 1.
[00156] [Table 2]
Transform
set Index
Transform
candidates 0
Transform
candidates 1
Transform
candidates 2
0 DST-VII DCT-II Transform skip
1 DST-VII DST-I Transform skip
2 DST-VII DCT-VIII Transform skip
[00157] Transform types of a horizontal transform
10 and a vertical transform of the current block may be
the same, or transform types of the horizontal
transform and the vertical transform may be different
from each other. For example, a transform type
candidate in the transform set may be applied to both
15 the horizontal transform and the vertical type, or a
different transform type candidate may be applied to
each of the horizontal transform and the vertical type.
[00158] As another example, transform sets for the
horizontal transform and the vertical transform of the
20 current block may be the same, or transform sets of
the horizontal transform and the vertical transform
may be different from each other. When different
transform sets are used for the horizontal transform
and the vertical transform, a transform set index for
25 identifying the transform set for the horizontal
transform and a transform set index for identifying
46
the transform set for the vertical transform may be
individually signaled.
[00159] For example, a transform set corresponding
to index 0 may be used for the horizontal transform,
5 and a transform set corresponding to index 1 may be
used for the vertical transform. If the current block
is 4x4 encoded with the intra prediction, the vertical
transform and the horizontal transform may use the
transform type candidate 1 included in each transform
10 set. Accordingly, DST-II may be used for the
horizontal transform and DST-I may be used for the
vertical transform.
[00160] It may be determined whether to use the
same transform set for the horizontal transform and
15 the vertical transform depending on an intra
prediction mode of the current block. For convenience
of explanation, the transform set for the horizontal
transform will be referred to as a horizontal
direction transform set, and the transform set for the
20 vertical transform will be referred to as a vertical
direction transform set.
[00161] For example, when the intra prediction mode
of the current block is similar to a horizontal
direction or similar to a vertical direction, the
25 horizontal transform and the vertical transform may
use different transform sets. Here, the intra
prediction mode similar to the horizontal direction
may include at least one of the vertical direction or
intra prediction modes in which a difference in mode
30 value from the intra prediction mode of the vertical
direction is less than a predefined value. In
47
addition, the intra-prediction mode similar to the
vertical direction may include at least one of the
horizontal direction or intra prediction modes in
which the difference in mode value from the intra
5 prediction mode of the horizontal direction is less
than a predefined value. On the other hand, when the
intra prediction mode of the current block is a non-
directional mode or a directional mode which does not
satisfy the above condition, the vertical transform
10 and the horizontal transform may use the same
transform set. Alternatively, it is also possible to
use different transform sets for the vertical
direction and the horizontal transform of the current
block when the intra prediction mode of the current
15 block is the non-directional mode.
[00162] FIG. 9 is a diagram illustrating, for 33
intra prediction modes, whether a vertical transform
and a horizontal transform use the same transform set.
In the example shown in Fig. 9, it is depicted that
20 the vertical and horizontal transforms use different
transform sets when the intra prediction mode of the
current block is included in a range of 7-13 or 23-29.
On the other hand, it is depicted that the same
transform set is applied to the vertical transform and
25 the horizontal transform when the intra prediction
mode of the current block is a directional mode not
included in the above range.
[00163] If there exists a block having the same
intra prediction mode as the current block in a
30 predetermined unit block, the transform set of the
current block may be set to be the same as the
48
transform set of the block having the same intra
prediction mode as the current block. Here, the
predetermined unit block may be a coding block, a
coding tree block, or a block having a predetermined
5 size.
[00164] For example, it will be assumed that an
intra prediction mode corresponding to a first
transform block in a scanning order in a coding block
has a vertical direction (for example, mode number
10 26), a horizontal direction transform set of the block
is index 2, and a vertical direction transform set of
the block is index 0. If there is more transform block
having an intra prediction mode of the vertical
direction in the coding block (i.e., a transform block
15 corresponding to a prediction block having the intra
prediction mode of the vertical direction), a
transform set index value is not signaled for the
newly scanned transform block. Instead, the transform
set of the previously scanned transform block having
20 the intra prediction mode of vertical direction is
applied as a transform set of the newly scanned
transform block. That is, a horizontal direction
transform set of the newly scanned transform block is
determined as the index 2, and a vertical direction
25 transform set is determined as the index 0.
[00165] As another example, when there is a block
having an intra prediction mode similar to the current
block in a predetermined unit block, the transform set
of the current block may be set to be the same as the
30 transform set of the block having the intra prediction
mode similar to the current block. Here, the intra
49
prediction mode similar to the current block may
include intra prediction modes within a predetermined
range from a reference intra prediction mode. For
example, when the reference intra prediction mode is a
5 horizontal direction or a vertical direction, the
reference intra prediction mode and the intra
prediction modes within ±a from the intra prediction
mode of the horizontal direction or the vertical
direction may be determined to be mutually similar.
10 [00166] For example, it will be assumed that an
intra prediction mode corresponding to a first
transform block in a scanning order in a coding block
has a vertical direction (for example, mode number
26), a horizontal direction transform set of the block
15 is index 2, and a vertical direction transform set of
the block is index 0. When there exists a transform
block having an intra prediction mode similar to the
vertical direction (e.g., mode number 27) in the
coding block (i.e., a transform block corresponding to
20 a prediction block having the vertical intra
prediction mode), a transform set index value may not
be signaled for the newly scanned transform block.
Instead, a transform set of the transform block having
the intra prediction mode that is similar to the intra
25 prediction mode of the current block may be applied as
the transform set of the newly scanned transform
block. That is, a horizontal direction transform set
of the newly scanned transform block is determined as
the index 2, and a vertical direction transform set
30 may be determined as the index 0.
[00167] At least one of a horizontal direction
50
transform set or a vertical direction transform set of
the current block may be determined based on an intra
prediction mode of the current block. For example,
Table 3 shows an example in which a fixed transform
5 set index is assigned according to the intra
prediction mode of the current block.
[00168] [Table 3]
Intra
Mode
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1
7
H 2 1 0 1 0 1 0 1 0 0 0 0 0 1 0 1 0 1
V 1 1 0 1 0 1 0 1 2 2 2 2 2 1 0 1 0 1
Intra
Mode
1
8
1
9
2
0
2
1
2
2
2
3
2
4
2
5
2
6
2
7
28 29 30 31 32 33 34
H 0 1 0 1 0 1 2 2 2 2 2 1 0 1 0 1 0
V 0 1 0 1 0 1 0 0 0 0 0 1 0 1 0 1 0
[00169] When the current block is encoded with the
inter prediction, a predefined transform set may be
10 used for the current block. For example, if the
current block is encoded with the inter prediction, a
transform set corresponding to index 0 may be used for
the current block.
[00170] Alternatively, when the coding block is
15 encoded with the inter prediction, a transform set is
selected for the coding block, and transform blocks
included in the coding block may use transform type
candidates included in the transform set of the coding
block. At this time, the transform type of each
20 transform block may be determined by a size or a shape
of the transform block, or information for identifying
the transform type selected for each transform block
may be signaled through the bitstream.
[00171] The determination of at least one of a
25 plurality of transform type candidate groups as the
51
transform type of the current block may be defined as
AMT (Adaptive Multiple Transform). The adaptive
multiple transform (AMT) may be applied to a coding
block of a specific size or a coding block of a
5 specific shape. At this time, information on the size
or the shape of the coding block to which the adaptive
multiple transform can be applied may be signaled
through the bitstream. Here, the information on the
size of the coding block may indicate at least one of
10 a maximum size or a minimum size. In addition, the
information may be signaled through at least one of a
block level, a slice header, or a sequence header.
[00172] Different transforms may be selectively
used based on different size/shape in a unit of a
15 slice or a block.
[00173] For example, in slice 0, DST may be used
when the transform block is encoded in the intra
prediction mode and a size of the transform block is
4×4, and DCT may be used in other cases. In slice 1,
20 DST may be used when the transform block is encoded in
the intra prediction mode and a size of the transform
block is less than or equal to 8x8, and DCT may be
used in other cases.
[00174] Different transforms may be selected based
25 on at least one of an intra prediction mode and the
number of samples in the transform block.
Specifically, for example, when the transform block is
encoded in the intra prediction mode and the number of
samples in transform block is 16 or less, the
30 transform may be performed using DST, and DCT may be
used in other blocks.
52
[00175] Specifically, for example, when the
transform block is encoded in the intra mode and the
transform block is 2x8 or when the transform block is
encoded in the intra mode and the transform block is
5 8x2, DST (Discrete Sine Transform) is used, and DCT-II
(Discrete Cosine Transform) is used in other blocks.
[00176] At this time, a syntax, different type
transform block selection indicator, indicating the
number of samples in a block which is used as a
10 reference for selecting different transforms may be
signaled in a slice header or a picture parameter set.
[00177] Conditions for selecting transform type
candidate 0 and conditions for selecting transform
type candidate 1 may differ in a unit of a sequence, a
15 slice, or a block. For example, in slice 0, the
transform type candidate 0 is selected only for a
transform block of 4x4 encoded in the intra mode,
while in the slice 0, the transform type 0 is selected
for a transform block of 8x8 or smaller encoded in the
20 intra mode.
[00178] Alternatively, the transform type may be
adaptively selected based on at least one of an intra
prediction mode or the number of samples in a block.
At this time, the number of samples in the block used
25 as a reference for selecting the transform type may
have a fixed value or may be determined through
information signaled through the bitstream. The
information may be signaled via a block level, a slice
header, or a picture parameter set.
30 [00179] For example, DST may be applied only when
the current block comprises 16 or less samples and
53
when the current block is encoded in the intra mode,
and DCT may be applied in other cases. Specifically,
DST may be applied to a transform block of 4x4, 2x8 or
8x2 encoded in the intra prediction, and DCT may be
5 applied to other blocks.
[00180] Although the above-described embodiments
have been described on the basis of a series of steps
or flowcharts, they do not limit the time-series order
of the invention, and may be performed simultaneously
10 or in different orders as necessary. Further, each of
the components (for example, units, modules, etc.)
constituting the block diagram in the above-described
embodiments may be implemented by a hardware device or
software, and a plurality of components. Or a plurality
15 of components may be combined and implemented by a
single hardware device or software. The above-described
embodiments may be implemented in the form of program
instructions that may be executed through various
computer components and recorded in a computer-readable
20 recording medium. The computer-readable recording
medium may include one of or combination of program
commands, data files, data structures, and the like.
Examples of computer-readable media include magnetic
media such as hard disks, floppy disks and magnetic
25 tape, optical recording media such as CD-ROMs and DVDs,
magneto-optical media such as floptical disks, media,
and hardware devices specifically configured to store
and execute program instructions such as ROM, RAM,
flash memory, and the like. The hardware device may be
30 configured to operate as one or more software modules
for performing the process according to the present
54
invention, and vice versa.
Industrial Applicability
[00181] The present invention may be applied to
5 electronic devices which is able to encode/decode a
video.
55
I/We Claim:
1. A method for decoding a video, the method
comprising:
5 obtaining a residual coefficient of a current
transform block;
inverse-quantizing the residual coefficient;
determining a transform type set of the current
transform block; and
10 obtaining a residual sample of the current
transform block by performing inverse-transform for
the current transform block based on the transform
type set,
characterized in that:
15 in response to a case where a coding block
including the current transform block is partitioned
into two transform blocks, the transform type set
of the current transform block is determined
differently between when the coding block is
20 partitioned in a horizontal direction and when the
coding block is partitioned in a vertical direction,
and
the coding block is obtained based on a tree-
based block division including at least one of a
25 quad division or a binary division.
2. The method of claim 1, wherein the transform type
set is constituted of a first transform type and a
second transform type,
56
wherein each of the first transform type and
the second transform type is representative of DCT
(Discrete Cosine Transform) 2, DST (Discrete Sine
Transform) 7 or DCT 8,
5 wherein the first transform type is used for a
horizontal transform for the current transform
block, and
wherein the second transform type is used for
a vertical transform for the current transform
10 block.
3. The method of claim 1, wherein the transform type
set of the current transform block is determined
differently between when the current transform block
15 is one of the two transform blocks and when the
current transform block is the other of the two
transform blocks.
4. The method of claim 1, wherein the method
20 comprises:
determining whether the transform type set of
the current transform block is determined explicitly
or implicitly,
wherein when it is determined that the
25 transform type set of the current transform block
is determined explicitly, the transform type set of
the current transform block is determined based on
index information explicitly signaled via a
bitstream, the index information specifying one of
57
a plurality of transform type sets, and
wherein when it is determined that the
transform type set of the current transform block
is determined implicitly, the transform type set of
5 the current transform block is determined without
parsing the index information from the bitstream.
5. The method of claim 4, wherein the determination
of whether the transform type set of the current
10 transform block is determined explicitly or
implicitly is based on a comparison between the size
of the current transform block and a threshold size.
6. A method for encoding a video, the method
15 comprising:
obtaining a residual sample of a current
transform block;
determining a transform type set of the current
transform block;
20 obtaining a transform coefficient of the
current transform block by performing transform for
the current transform block based on the transform
type set; and
obtaining a residual coefficient by quantizing
25 the transform coefficient,
characterized in that:
in response to a case where a coding block
including the current transform block is partitioned
into two transform blocks, the transform type set
58
of the current transform block is determined
differently between when the coding block is
partitioned in a horizontal direction and when the
coding block is partitioned in a vertical direction,
5 and
the coding block is obtained based on a tree-
based block division including at least one of a
quad division or a binary division.
10 7. A method of storing or transmitting compressed
video data generated by an encoding method of claim
6.
8. A device for transmitting compressed video data,
15 comprising:
a processor configured to obtain the compressed
video data; and
a transmitter configured to transmit the
compressed video data,
20 wherein obtaining the compressed video data
comprises:
obtaining a residual sample of a current
transform block;
determining a transform type set of the current
25 transform block;
obtaining a transform coefficient of the
current transform block by performing transform for
the current transform block based on the transform
type set; and
59
obtaining a residual coefficient by quantizing
the transform coefficient,
characterized in that:
in response to a case where a coding block
5 including the current transform block is partitioned
into two transform blocks, the transform type set
of the current transform block is determined
differently between when the coding block is
partitioned in a horizontal direction and when the
10 coding block is partitioned in a vertical direction,
and
the coding block is obtained based on a tree-
based block division including at least one of a
quad division or a binary division.
15
60
Date 10 July 2025
MALATHI LAKSHMIKUMARAN
IN/PA-1433
Agent for the Applicant
To,
The Controller of Patents
The Patent Office at New Delhi
ABSTRACT
METHOD AND APPARATUS FOR PROCESSING VIDEO SIGNAL
A method for decoding a video according to the
present invention may comprise: deriving a spatial
5 merge candidate for a current block, generating a merge
candidate list for the current block based on the
spatial merge candidate, obtaining motion information
for the current block based on the merge candidate
list, and performing motion compensation for the
10 current block based on the motion information. Herein,
if the current block does not have a pre-defined shape
or a size equal to or greater than a pre-defined size,
the spatial merge candidate of the current block may be
derived based on a block which have the pre-defined
15 shape or a size equal to or greater than the pre-
defined size, the block including the current block.
61
, Claims:I/We Claim:
1. A method for decoding a video, the method
comprising:
5 obtaining a residual coefficient of a current
transform block;
inverse-quantizing the residual coefficient;
determining a transform type set of the current
transform block; and
10 obtaining a residual sample of the current
transform block by performing inverse-transform for
the current transform block based on the transform
type set,
characterized in that:
15 in response to a case where a coding block
including the current transform block is partitioned
into two transform blocks, the transform type set
of the current transform block is determined
differently between when the coding block is
20 partitioned in a horizontal direction and when the
coding block is partitioned in a vertical direction,
and
the coding block is obtained based on a tree-
based block division including at least one of a
25 quad division or a binary division.
2. The method of claim 1, wherein the transform type
set is constituted of a first transform type and a
second transform type,
wherein each of the first transform type and
the second transform type is representative of DCT
(Discrete Cosine Transform) 2, DST (Discrete Sine
Transform) 7 or DCT 8,
5 wherein the first transform type is used for a
horizontal transform for the current transform
block, and
wherein the second transform type is used for
a vertical transform for the current transform
10 block.
3. The method of claim 1, wherein the transform type
set of the current transform block is determined
differently between when the current transform block
15 is one of the two transform blocks and when the
current transform block is the other of the two
transform blocks.
4. The method of claim 1, wherein the method
20 comprises:
determining whether the transform type set of
the current transform block is determined explicitly
or implicitly,
wherein when it is determined that the
25 transform type set of the current transform block
is determined explicitly, the transform type set of
the current transform block is determined based on
index information explicitly signaled via a
bitstream, the index information specifying one of
a plurality of transform type sets, and
wherein when it is determined that the
transform type set of the current transform block
is determined implicitly, the transform type set of
5 the current transform block is determined without
parsing the index information from the bitstream.
5. The method of claim 4, wherein the determination
of whether the transform type set of the current
10 transform block is determined explicitly or
implicitly is based on a comparison between the size
of the current transform block and a threshold size.
6. A method for encoding a video, the method
15 comprising:
obtaining a residual sample of a current
transform block;
determining a transform type set of the current
transform block;
20 obtaining a transform coefficient of the
current transform block by performing transform for
the current transform block based on the transform
type set; and
obtaining a residual coefficient by quantizing
25 the transform coefficient,
characterized in that:
in response to a case where a coding block
including the current transform block is partitioned
into two transform blocks, the transform type set
of the current transform block is determined
differently between when the coding block is
partitioned in a horizontal direction and when the
coding block is partitioned in a vertical direction,
5 and
the coding block is obtained based on a tree-
based block division including at least one of a
quad division or a binary division.
10 7. A method of storing or transmitting compressed
video data generated by an encoding method of claim
6.
8. A device for transmitting compressed video data,
15 comprising:
a processor configured to obtain the compressed
video data; and
a transmitter configured to transmit the
compressed video data,
20 wherein obtaining the compressed video data
comprises:
obtaining a residual sample of a current
transform block;
determining a transform type set of the current
25 transform block;
obtaining a transform coefficient of the
current transform block by performing transform for
the current transform block based on the transform
type set; and
obtaining a residual coefficient by quantizing
the transform coefficient,
characterized in that:
in response to a case where a coding block
5 including the current transform block is partitioned
into two transform blocks, the transform type set
of the current transform block is determined
differently between when the coding block is
partitioned in a horizontal direction and when the
10 coding block is partitioned in a vertical direction,
and
the coding block is obtained based on a tree-
based block division including at least one of a
quad division or a binary division.