3.2
adaptive colour transform (ACT): A cross-component transform
applied to the decoded residual of a coding unit in the 4:4:4
colour format prior to reconstruction and loop filtering.
3.3
adaptive loop filter (ALF): A filtering process that is applied as
part of the decoding process and is controlled by parameters conveyed in
an APS.
3.4
AC transform coefficient: Any transform coefficient for which the frequency index in at least one of the two dimensions is non-zero.
3.5
ALF APS: An APS that controls the ALF process.
3.6
adaptation parameter set (APS): A syntax
structure containing syntax elements
that apply to zero or more slices as
determined by zero or more syntax
elements found in slice headers.
3.7
associated GDR picture: The previous GDR picture (when present) in decoding order,
for a particular picture with nuh_layer_id equal to a particular value layerId,
that has nuh_layer_id equal to layerId and between which and the particular picture
in decoding order there is no IRAP picture with nuh_layer_id
equal to layerId.
3.8
associated GDR subpicture: The previous GDR subpicture (when present) in decoding order, for a particular subpicture with nuh_layer_id equal
to a particular value layerId and subpicture index equal to a particular value
subpicIdx, that has nuh_layer_id equal to layerId and subpicture index equal to
subpicIdx and between which and the particular subpicture in decoding
order there is no IRAP subpicture with nuh_layer_id equal to layerId
and subpicture index equal to subpicIdx.
3.9
associated IRAP picture: The previous IRAP picture (when present) in decoding
order, for a particular picture with nuh_layer_id equal to a particular
value layerId, that has nuh_layer_id
equal to layerId and between which and the particular picture in decoding
order there is no GDR picture with nuh_layer_id equal to layerId.
3.10
associated IRAP subpicture: The previous IRAP subpicture (when present) in decoding order, for a particular subpicture with nuh_layer_id equal
to a particular value layerId and subpicture index equal to a particular value
subpicIdx, that has nuh_layer_id equal to layerId and subpicture index equal to
subpicIdx and between which and the particular subpicture in decoding
order there is no GDR subpicture with nuh_layer_id equal to layerId
and subpicture index equal to subpicIdx.
3.11
associated non-VCL NAL unit: A non-VCL NAL unit (when
present) for a VCL NAL unit where the
VCL NAL unit is the associated VCL NAL unit of the non-VCL NAL unit.
3.12
associated VCL NAL unit: The preceding VCL NAL unit in decoding order for a non-VCL NAL unit with nal_unit_type
equal to EOS_NUT, EOB_NUT, SUFFIX_APS_NUT, SUFFIX_SEI_NUT, FD_NUT, RSV_NVCL_27,
UNSPEC_30, or UNSPEC_31; or otherwise the next VCL NAL unit in decoding
order.
3.13
bin: One bit of a bin
string.
3.14
binarization: A set of bin
strings for all possible values of a syntax
element.
3.16
binary split: A split of
a rectangular MxN block of samples into two blocks where a vertical split results in a first (M / 2)xN
block and a second (M / 2)xN
block, and a horizontal split results
in a first Mx(N / 2) block
and a second Mx(N / 2) block.
3.18
bi-predictive (B) slice: A slice
that is decoded using intra prediction or using inter
prediction with at most two motion vectors and reference
indices to predict the sample values of each block.
3.19
bitstream: A sequence
of bits, in the form of a NAL unit stream or a byte stream, that
forms the representation of a sequence of AUs forming one or more coded video sequences (CVSs).
3.20
block: An MxN
(M-column by N-row) array of samples, or an MxN array of transform
coefficients.
3.21
block vector: A two-dimensional vector that provides an offset
from the coordinates of the current coding
block to the coordinates of the reference block in the same decoded slice.
3.22
byte: A sequence of 8
bits, within which, when written or read as a sequence of bit values, the
left-most and right-most bits represent the most and least significant bits,
respectively.
3.23
byte-aligned: A
position in a bitstream is byte-aligned
when the position is an integer multiple of 8 bits from the position of the
first bit in the bitstream, and a bit or byte
or syntax element is said to be
byte-aligned when the position at which it appears in a bitstream is byte-aligned.
3.24
byte stream: An
encapsulation of a NAL unit stream into a series of bytes containing
start code prefixes and NAL units.
3.25
chroma: A sample
array or single sample representing one of the two colour difference signals
related to the primary colours, represented by the symbols Cb and Cr.
NOTE – The term chroma is used
rather than the term chrominance in order to avoid the implication of the use
of linear light transfer characteristics that is often associated with the term
chrominance.
3.26
clean random access (CRA) PU: A PU in which the coded picture is a CRA
picture.
3.27
clean random access (CRA) picture: An IRAP picture for which each VCL NAL
unit has nal_unit_type equal to CRA_NUT.
NOTE – A CRA picture does not use inter prediction in its decoding process, and could be the first picture in the bitstream in
decoding order, or could appear later in the bitstream. A CRA picture could have
associated RADL or RASL pictures. When a
CRA picture has NoOutputBeforeRecoveryFlag equal to 1, the associated RASL
pictures are not output by the decoder, because they might not be decodable, as
they could contain references to pictures that are not present in the
bitstream.
3.28
clean random access (CRA) subpicture: An IRAP subpicture for which each VCL NAL
unit has nal_unit_type equal to CRA_NUT.
3.29
coded layer video sequence (CLVS): A sequence of PUs
with the same value of nuh_layer_id that consists, in decoding order, of a CLVSS PU,
followed by zero or more PUs that are
not CLVSS PUs, including all
subsequent PUs up to but not
including any subsequent PU that is a
CLVSS PU.
NOTE – A CLVSS PU could be an IDR
PU, a CRA PU, or a GDR PU. The value of NoOutputBeforeRecoveryFlag is equal to
1 for each IDR PU, and each CRA PU that has HandleCraAsClvsStartFlag equal to
1, and each CRA or GDR PU that is the first PU in the layer of the bitstream in
decoding order or the first PU in the layer of the bitstream that follows an EOS
NAL unit in the layer in decoding order.
3.30
coded layer video sequence start (CLVSS) PU: A PU in
which the coded picture is a CLVSS picture.
3.31
coded layer video sequence start (CLVSS) picture: A coded
picture that is an IRAP picture
with NoOutputBeforeRecoveryFlag equal to 1 or a GDR picture with NoOutputBeforeRecoveryFlag equal to 1.
3.32
coded picture: A coded representation of a picture comprising
VCL NAL units with a particular value
of nuh_layer_id within an AU and containing all CTUs
of the picture.
3.33
coded picture buffer (CPB): A first-in first-out buffer containing DUs in decoding order specified in the hypothetical
reference decoder in Annex C.
3.34
coded representation:
A data element as represented in its coded form.
3.35
coded video sequence (CVS): A sequence of AUs that
consists, in decoding order, of a CVSS AU, followed by zero or more AUs that are not CVSS AUs, including all subsequent AUs up to but not including any subsequent AU that is a CVSS AU.
3.36
coded video sequence start (CVSS) AU: An IRAP AU or GDR AU for which the coded picture in each PU is a CLVSS picture.
3.37
coding block: An MxN block of samples for some values of M
and N such that the division of a CTB
into coding blocks is a partitioning.
3.38
coding tree block (CTB): An N×N block of samples for some
value of N such that the division of a component
into CTBs is a partitioning.
3.39
coding tree unit (CTU): A CTB of luma samples, two corresponding CTBs of chroma
samples of a picture that has three
sample arrays, or a CTB of samples of a monochrome picture, and syntax
structures used to code the samples.
3.40
coding unit (CU): A coding block of luma
samples, two corresponding coding blocks of chroma samples of a picture that has three sample arrays in the
single tree mode, or a coding block of luma samples of a picture that has three sample arrays in the
dual tree mode, or two coding blocks of chroma samples of a picture that has three sample arrays in the
dual tree mode, or a coding block of samples of a monochrome picture, and syntax structures used to code the samples.
3.41
component: An array
or single sample from one of the three arrays (luma and two chroma)
that compose a picture in
4:2:0, 4:2:2, or 4:4:4 colour format or the array or a single sample of the
array that compose a picture in monochrome format.
3.42
context variable: A
variable specified for the adaptive
binary arithmetic decoding process
of a bin by an equation containing recently decoded bins.
3.43
deblocking filter: A
filtering process that is applied as part of the decoding process in
order to minimize the appearance of visual artefacts at the boundaries between blocks.
3.44
decoded picture: A picture
produced by applying the decoding process to a coded picture.
3.45
decoded picture buffer (DPB): A buffer holding decoded pictures for reference, output
reordering, or output delay specified for the hypothetical reference decoder.
3.46
decoder: An
embodiment of a decoding process.
3.47
decoding order: The
order in which syntax elements are
processed by the decoding process.
3.49
decoding unit (DU):
An AU if DecodingUnitHrdFlag is equal
to 0 or a subset of an AU otherwise,
consisting of one or more VCL NAL units
in an AU and the associated non-VCL NAL units.
3.50
emulation prevention byte: A byte equal to 0x03 that is
present within a NAL unit when the syntax
elements of the bitstream form
certain patterns of byte values in a
manner that ensures that no sequence of consecutive byte-aligned bytes in the
NAL unit can contain a start code prefix.
3.51
encoder: An
embodiment of an encoding process.
3.52
encoding process: A
process not specified in this Specification that produces a bitstream
conforming to this Specification.
3.53
filler data NAL units: NAL
units with nal_unit_type equal to FD_NUT.
3.54
flag: A variable or
single-bit syntax element that can
take one of the two possible values: 0 and 1.
3.55
frequency index: A one-dimensional or two-dimensional index associated
with a transform coefficient prior to
the application of a transform in the
decoding process.
3.56
gradual decoding refresh (GDR) AU: An AU in
which there is a PU for each layer present in the CVS and the
coded picture in each present PU is a GDR picture.
3.57
gradual decoding refresh (GDR) PU: A PU in
which the coded picture is a GDR picture.
3.58
gradual decoding
refresh (GDR) picture: A picture for which each VCL NAL unit has nal_unit_type
equal to GDR_NUT.
NOTE – The value of pps_mixed_nalu_types_in_pic_flag for a GDR picture
is equal to 0. When pps_mixed_nalu_types_in_pic_flag
is equal to 0 for a picture, and any slice of the picture has nal_unit_type
equal to GDR_NUT, all other
slices of the picture have the same value of nal_unit_type, and the picture is
known to be a GDR picture after receiving the first slice.
3.59
gradual decoding
refresh (GDR) subpicture: A subpicture for which each VCL NAL unit
has nal_unit_type equal to GDR_NUT.
3.60
hypothetical reference decoder (HRD): A hypothetical decoder model that specifies
constraints on the variability of conforming NAL unit streams or
conforming byte streams that an
encoding process may produce.
3.61
hypothetical stream scheduler (HSS): A hypothetical delivery mechanism used for checking
the conformance of a bitstream or a decoder with regards to the timing and
data flow of the input of a bitstream into
the hypothetical reference decoder.
3.62
instantaneous decoding refresh (IDR) PU: A PU
in which the coded picture is an IDR picture.
3.63
instantaneous decoding refresh (IDR) picture: An IRAP picture for which each VCL NAL unit has nal_unit_type equal to
IDR_W_RADL or IDR_N_LP.
NOTE – An IDR picture does not use inter prediction in its decoding process, and could be the first picture in the bitstream in
decoding order, or could appear later in the bitstream. Each IDR picture is the
first picture of a CVS in decoding order. When an IDR picture for which each
VCL NAL unit has nal_unit_type equal to IDR_W_RADL, it could have associated
RADL pictures. When an IDR picture for which each VCL NAL unit has nal_unit_type
equal to IDR_N_LP, it does not have any associated leading pictures. An IDR
picture does not have associated RASL pictures.
3.64
instantaneous decoding refresh (IDR) subpicture: An IRAP subpicture for
which each VCL NAL unit has
nal_unit_type equal to IDR_W_RADL or IDR_N_LP.
3.65
inter-layer reference picture (ILRP): A
picture in the same AU with the current picture, with nuh_layer_id less than the nuh_layer_id of
the current picture, and is marked as "used for long-term
reference".
3.66
inter coding: Coding
of a coding block, slice, or picture that uses inter
prediction.
3.67
inter prediction: A prediction
derived from blocks of sample values of one or more reference pictures as determined by motion vectors.
3.69
intra coding: Coding
of a coding block, slice,
or picture that uses intra prediction.
3.70
intra prediction: A prediction
derived from neighbouring sample values of the same decoded slice.
3.71
intra random access point (IRAP) AU: An AU in
which there is a PU for each layer present
in the CVS and the coded picture in
each PU is an IRAP picture.
3.72
intra random access point (IRAP) PU: A PU in
which the coded picture is an IRAP picture.
3.73
intra random access point (IRAP) picture: A coded
picture for which all VCL
NAL units have the same value of nal_unit_type in the range of IDR_W_RADL to CRA_NUT, inclusive.
NOTE 1 – An IRAP picture could be a CRA picture or an IDR picture. An
IRAP picture does not use inter prediction from reference pictures in the same
layer in its decoding process. The first picture in the bitstream in decoding
order is an IRAP or GDR picture. For a single-layer bitstream, provided the
necessary parameter sets are available when they need to be referenced, the
IRAP picture and all subsequent non-RASL pictures in the CLVS in decoding order
are correctly decodable without performing the decoding process of any pictures
that precede the IRAP picture in decoding order.
NOTE 2 – The value of pps_mixed_nalu_types_in_pic_flag
for an IRAP picture is equal to 0. When pps_mixed_nalu_types_in_pic_flag is equal to 0 for a
picture, and any slice of the picture has nal_unit_type in the range of IDR_W_RADL to CRA_NUT, inclusive, all other slices of the picture have the same
value of nal_unit_type, and the picture is known to be an IRAP picture after receiving the first slice.
3.74
intra
random access point (IRAP) subpicture: A
subpicture for which all VCL NAL units have the same value of
nal_unit_type in the range of IDR_W_RADL to
CRA_NUT, inclusive.
3.75
intra (I) slice: A slice
that is decoded using intra
prediction only.
3.76
layer: A set of VCL NAL units that all have a particular
value of nuh_layer_id and the associated
non-VCL NAL units.
3.77
leading picture: A picture
that precedes the associated IRAP picture in output order.
3.78
leading subpicture: A
subpicture that precedes the associated IRAP subpicture in output
order.
3.79
leaf: A terminating node of a tree that is a root node of
a tree of depth 0.
3.80
level: A defined set
of constraints on the values that may be taken by the syntax elements and variables of this Specification, or the value
of a transform coefficient prior to scaling.
NOTE – The same set of levels is
defined for all profiles, with most aspects of the definition of each level
being in common across different profiles. Individual implementations could,
within the specified constraints, support a different level for each supported
profile.
3.81
list 0 (list 1) motion vector: A motion vector associated with a reference index pointing
into reference picture list 0 (list
1).
3.82
list 0 (list 1) prediction: Inter prediction of the content of a slice using a reference
index pointing into reference picture list 0 (list 1).
3.83
LMCS APS: An APS that controls the LMCS
process.
3.84
long-term reference picture (LTRP): A picture with
nuh_layer_id equal to the nuh_layer_id of the current picture and marked as
"used for long-term reference".
3.85
luma: A sample array
or single sample representing the monochrome signal related to the primary
colours, represented by the symbol or subscript Y or L.
NOTE – The term luma is used
rather than the term luminance in order to avoid implying the use of linear
light transfer characteristics that is often associated with the term
luminance. The symbol L is sometimes used instead of the symbol Y to avoid
confusion with the symbol y as used for vertical location.
3.86
luma mapping with chroma scaling (LMCS): A process that is applied as part of the decoding
process that maps luma samples to particular values and in some
cases also applies a scaling operation to the values of chroma samples.
3.87
motion vector: A
two-dimensional vector used for inter prediction that provides an offset
from the coordinates in the decoded picture to the coordinates in a reference
picture.
3.88
multi-type tree: A tree in which a parent node can be split
either into two child nodes using a binary
split or into three child nodes using a ternary
split, each of which could become the parent node for another split into either
two or three child nodes.
3.89
network abstraction layer (NAL) unit: A syntax
structure containing an indication of the type of data to follow and bytes containing that data in the form
of an RBSP interspersed as necessary
with emulation prevention bytes.
3.90
network abstraction layer (NAL) unit stream: A sequence of NAL units.
3.91
operation point (OP): A temporal subset of an OLS, identified
by an OLS index and a highest value of TemporalId.
3.92
output layer: A layer of an output layer set that is output.
3.93
output layer set (OLS): A set of layers for which one or more
layers are specified as the output layers.
3.94
output layer set (OLS) layer index: An index, of a layer in an OLS, to the
list of layers in the OLS.
3.95
output order: The
order of pictures or subpictures within a CLVS indicated by increasing POC
values, and for decoded pictures that are output from DPB, this is the order in
which the decoded pictures are output from the DPB.
3.96
output time: A time when a decoded
picture is to be output from the DPB (for the decoded pictures that are to be output from the DPB) as specified by the HRD according to the output timing DPB operation.
3.97
palette: A set of
representative component values. (PLT)
3.98
palette prediction: A
prediction derived from one or more palettes.
3.99
partitioning: The
division of a set into subsets such that each element of the set is in exactly
one of the subsets.
3.100
picture: An array of luma samples in monochrome format or an
array of luma samples and two
corresponding arrays of chroma
samples in 4:2:0, 4:2:2, and 4:4:4 colour format.
NOTE – A
picture is either a frame or a field. However, in one CVS, either all pictures
are frames or all pictures are fields.
3.101
picture header (PH): A syntax
structure containing syntax elements
that apply to all slices of a coded
picture.
3.102
picture-level slice index: An index, defined when pps_rect_slice_flag is equal to 1, of a slice to
the list of slices in a picture in the order as the slices are signalled in the
PPS when pps_single_slice_per_subpic_flag is equal to 0,
or in the order of increasing subpicture indices of the subpicture
corresponding to the slices when pps_single_slice_per_subpic_flag is equal to 1.
3.103
picture order count (POC): A variable that is associated with each picture, uniquely identifies the associated picture among all pictures
in the CLVS, and, when the associated
picture is to be output from the DPB, indicates the position of the
associated picture in output order relative to the output order positions of the other pictures in the same CLVS that are to be output from the DPB.
3.104
picture parameter set (PPS): A syntax
structure containing syntax elements
that apply to zero or more entire coded
pictures as determined by a syntax
element found in each picture header.
3.105
picture unit (PU): A set of NAL units that are associated with each other according to a specified classification
rule, are consecutive in decoding order,
and contain exactly one coded picture.
3.106
prediction: An
embodiment of the prediction process.
3.107
prediction process:
The use of a predictor to provide an estimate of the data element (e.g.,
sample value or motion vector) currently being decoded.
3.108
predictive (P) slice: A slice
that is decoded using intra prediction or using inter prediction with at most one motion
vector and reference index to predict the sample values of
each block.
3.110
profile: A specified
subset of the syntax of this Specification.
3.111
quadtree: A tree in which a
parent node can be split into four child nodes, each of which could become the parent
node for another split into four child nodes.
3.112
quantization parameter: A variable used by the decoding process for scaling of transform
coefficient levels.
3.113
random access: The
act of starting the decoding process for a bitstream at a point other than the
beginning of the bitstream.
3.114
random access decodable leading (RADL) PU: A PU
in which the coded picture is a RADL picture.
3.115
random access decodable leading (RADL)
picture: A coded picture for which each VCL NAL unit has nal_unit_type equal to
RADL_NUT.
NOTE – All RADL pictures are
leading pictures. A RADL picture with nuh_layer_id equal to layerId is not used
as a reference picture for the decoding process of any picture with
nuh_layer_id equal to layerId that follows, in output order, the IRAP picture
associated with the RADL picture. When sps_field_seq_flag is equal to 0, all
RADL pictures, when present, precede, in decoding order, all non-leading
pictures of the same associated IRAP picture.
3.116
random access decodable leading
(RADL) subpicture: A subpicture for which each VCL
NAL unit has nal_unit_type equal to RADL_NUT.
3.117
random access skipped leading (RASL) PU: A PU
in which the coded picture is a RASL picture.
3.118
random access skipped leading (RASL)
picture: A coded picture for which there is at
least one VCL NAL unit with nal_unit_type equal to RASL_NUT and other
VCL NAL units all have nal_unit_type equal to RASL_NUT or RADL_NUT.
NOTE – All RASL pictures are
leading pictures of an associated CRA picture. When the associated CRA picture
has NoOutputBeforeRecoveryFlag equal to 1, the RASL picture is not output and might
not be correctly decodable, as the RASL picture could contain references to
pictures that are not present in the bitstream. RASL pictures are not used as
reference pictures for the decoding process of non-RASL pictures in the same
layer, except that a RADL subpicture, when present, in a RASL picture in the
same layer could be used for inter prediction of the collocated RADL subpicture
in a RADL picture that is associated with the same CRA picture as the RASL
picture. When sps_field_seq_flag is equal to 0, all RASL pictures, when
present, precede, in decoding order, all non-leading pictures of the same
associated CRA picture.
3.119
random access skipped leading
(RASL) subpicture: A subpicture for which each VCL NAL unit has nal_unit_type
equal to RASL_NUT.
3.120
raster scan: A
mapping of a rectangular two-dimensional pattern to a one-dimensional pattern
such that the first entries in the one-dimensional pattern are from the first
top row of the two-dimensional pattern scanned from left to right, followed
similarly by the second, third, etc., rows of the pattern (going down) each
scanned from left to right.
3.123
reference index: An
index into a reference picture list.
3.124
reference picture: A picture
that is a short-term reference
picture, a long-term reference
picture, or an inter-layer reference
picture.
NOTE – A reference picture
contains samples that could be used for inter prediction in the decoding
process of subsequent pictures in decoding order.
3.125
reference picture list (RPL): A list of reference pictures
that is used for inter prediction of a P
or B slice.
NOTE – Two RPLs, RPL 0 and RPL 1, are generated for each slice of a
picture. The set of unique
pictures referred to by all entries in the two RPLs associated with a picture
consists of all reference pictures that could be used for inter prediction of
the associated picture or any picture following the associated picture in
decoding order. For the decoding process of a P slice,
only RPL 0 is used
for inter prediction. For the decoding process
of a B slice, both RPL 0 and RPL 1 are used for inter prediction. For decoding the slice data of an I slice, no
RPL is used for for inter prediction.
3.126
reference picture list 0: The reference picture list
used for inter prediction of a P
slice or the first of the two reference
picture lists used for inter
prediction of a B slice.
3.127
reference picture list 1: The second reference picture list
used for inter prediction of a B slice.
3.128
residual: The decoded
difference between a prediction of a sample or data element and its
decoded value.
3.129
scaling: The process
of multiplying transform
coefficient levels by a factor, resulting
in transform coefficients.
3.130
scaling list: A list
that associates each frequency index with a scale factor for the scaling
process.
3.131
scaling list APS: An APS
with syntax elements used to construct the scaling lists.
3.132
sequence parameter set (SPS): A syntax
structure containing syntax elements
that apply to zero or more entire CLVSs
as determined by the content of a syntax
element found in the PPS referred
to by a syntax element found in each picture header.
3.133
short-term reference picture (STRP): A picture with nuh_layer_id equal to the
nuh_layer_id of the current picture
and marked as "used for short-term reference".
3.134
slice: An integer number of complete tiles or an integer number of consecutive complete CTU rows within a tile of a picture that are exclusively contained in a
single NAL unit.
3.135
slice header: A part of a coded slice containing the data elements
pertaining to all tiles or CTU rows within a tile represented in the slice.
3.136
source: A term used
to describe the video material or some of its attributes before encoding.
3.137
start code prefix: A
unique sequence of three bytes equal
to 0x000001 embedded in the byte stream as a prefix to each NAL unit.
NOTE – The location of a start code prefix can be used by a
decoder to identify the beginning of a new NAL unit and the end of a previous NAL unit. Emulation of start
code prefixes is prevented within NAL
units by the inclusion of emulation prevention bytes.
3.138
step-wise temporal sublayer access (STSA) PU: A PU
in which the coded picture is an STSA picture.
3.139
step-wise temporal sublayer access (STSA)
picture: A coded picture for which each VCL NAL unit has nal_unit_type equal to
STSA_NUT.
NOTE – An STSA picture does not
use pictures in the same layer and with the same TemporalId as the STSA picture
for inter prediction reference. Pictures following an STSA picture in decoding
order in the same layer and with the same TemporalId as the STSA picture do not
use pictures prior to the STSA picture in decoding order in the same layer and
with the same TemporalId as the STSA picture for inter prediction reference. An
STSA picture enables up-switching, at the STSA picture, to the sublayer
containing the STSA picture, from the immediately lower sublayer of the same
layer when the coded
picture does not belong to the lowest sublayer. STSA pictures in an independent
layer always have TemporalId greater than 0.
3.140
step-wise temporal sublayer access
(STSA) subpicture: A subpicture for which each VCL
NAL unit has nal_unit_type equal to STSA_NUT.
3.141
string of data bits (SODB): A sequence of some number of bits representing syntax elements present within a raw byte sequence payload
prior to the raw byte sequence payload stop bit, where the left-most bit
is considered to be the first and most significant bit, and the right-most bit
is considered to be the last and least significant bit.
3.142
sub-bitstream extraction
process: A specified process by which NAL
units in a bitstream that do not
belong to a target set, determined by a target OLS index and a target highest
TemporalId, are removed from the bitstream,
with the output sub-bitstream consisting of the NAL units in the bitstream that belong to the target set.
3.143
sublayer: A temporal scalable layer of a temporal scalable bitstream, consisting of VCL NAL units with a particular value of
the TemporalId variable and the associated non-VCL
NAL units.
3.144
sublayer representation: A subset of the bitstream consisting of NAL
units of a particular sublayer
and the lower sublayers.
3.145
subpicture: A rectangular region
of one or more slices within a picture.
3.146
subpicture-level slice index: An index, defined when pps_rect_slice_flag is equal
to 1, of a slice to the list of slices in a
subpicture in the order as they are signalled in the PPS.
3.147
supplemental enhancement information (SEI) message: A syntax
structure with specified semantics that conveys a particular type of information
that assists in processes
related to decoding, display or other purposes
but is not needed by the decoding process in order to determine the
values of the samples in decoded pictures.
3.148
syntax element: An
element of data represented in the bitstream.
3.149
syntax structure:
Zero or more syntax elements present
together in the bitstream in a
specified order.
3.150
ternary split: A split of a rectangular MxN block of samples
into three blocks where a vertical split
results in a first (M / 4)xN block,
a second (M / 2)xN block, a
third (M / 4)xN block, and
a horizontal split results in a first Mx(N / 4) block, a second Mx(N / 2) block, a third Mx(N / 4) block.
3.151
tier: A specified category of level constraints imposed on values of the syntax elements in the bitstream,
where the level constraints are
nested within a tier and a decoder conforming to a certain tier and level would be capable of decoding all bitstreams that conform to the same tier or the lower tier of
that level or any level below it.
3.152
tile: A rectangular
region of CTUs within a particular tile column and a particular tile row in a picture.
3.153
tile column: A
rectangular region of CTUs having a
height equal to the height of the picture
and a width specified by syntax elements
in the picture parameter set.
3.154
tile row: A
rectangular region of CTUs having a
height specified by syntax elements
in the picture parameter set and a
width equal to the width of the picture.
3.155
tile scan: A specific
sequential ordering of CTUs partitioning a picture in which the CTUs
are ordered consecutively in CTU raster scan in a tile whereas tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture.
3.156
trailing picture: A picture
for which each VCL NAL unit has nal_unit_type equal to TRAIL_NUT.
NOTE – Trailing pictures
associated with an IRAP or GDR picture also follow the IRAP or GDR picture in
decoding order. Pictures that follow the associated IRAP picture in output
order and precede the associated IRAP picture in decoding order are not
allowed.
3.157
trailing subpicture: A
subpicture for which each VCL NAL
unit has nal_unit_type equal to TRAIL_NUT.
NOTE – Trailing subpictures
associated with an IRAP or GDR subpicture also follow the IRAP or GDR
subpicture in decoding order. Subpictures that follow the associated IRAP
subpicture in output order and precede the associated IRAP subpicture in
decoding order are not allowed.
3.158
transform: A part of
the decoding process by which a block of transform coefficients is converted to a block of spatial-domain values.
3.159
transform block: A
rectangular MxN block of samples resulting from a transform in the decoding
process.
3.160
transform coefficient:
A scalar quantity, considered to be in a frequency domain, that is associated
with a particular one-dimensional or two-dimensional frequency index in a transform in the decoding process.
3.161
transform coefficient level: An integer quantity representing the value associated with a particular
two‑dimensional frequency index in the decoding
process prior to scaling for
computation of a transform coefficient
value.
3.162
transform unit (TU):
A transform block of luma samples and two corresponding transform blocks of chroma samples of a picture when using a single coding
unit tree for luma and chroma; or, a transform block of luma
samples or two transform blocks of chroma samples when using two separate coding unit trees for luma and chroma, and syntax structures
used to transform the transform block
samples.
3.163
tree: A tree is a finite set of nodes with a unique root
node.
3.164
video coding layer (VCL) NAL unit: A collective term for coded slice NAL units and the subset of NAL units that have reserved values of nal_unit_type that are classified as VCL NAL
units in this Specification.
1
Abbreviations
For the purposes
of this Recommendation | International Standard, the following abbreviations
apply.
ACT adaptive
colour transform
ALF adaptive
loop filter
AMVR adaptive
motion vector resolution
APS adaptation parameter
set
AU access unit
AUD access unit delimiter
AVC advanced video coding
(Rec. ITU-T H.264 | ISO/IEC
14496-10)
B bi-predictive
BCW bi-prediction
with CU-level weights
BDOF bi-directional
optical flow
BDPCM block-based
delta pulse code modulation
BP buffering
period
CABAC context-based
adaptive binary arithmetic coding
CB coding
block
CBR constant
bit rate
CCALF cross-component adaptive loop
filter
CPB coded
picture buffer
CRA clean
random access
CRC cyclic
redundancy check
CTB coding
tree block
CTU coding
tree unit
CU coding
unit
CVS coded
video sequence
DPB decoded
picture buffer
DCI decoding
capability information
DRAP dependent
random access point
DU decoding
unit
DUI decoding
unit information
EG exponential-Golomb
EGk k-th
order exponential-Golomb
EOB end
of bitstream
EOS end
of sequence
FD filler
data
FIFO first-in,
first-out
FL fixed-length
GBR green,
blue, and red
GCI general
constraints information
GDR gradual
decoding refresh
GPM geometric
partitioning mode
HMVP history-based motion vector prediction
HEVC high
efficiency video coding (Rec. ITU-T H.265 | ISO/IEC 23008-2)
HRD hypothetical
reference decoder
HSS hypothetical
stream scheduler
I intra
IBC intra
block copy
IDR instantaneous
decoding refresh
ILRP inter-layer
reference picture
IRAP intra
random access point
LFNST low
frequency non-separable transform
LPS least
probable symbol
LSB least
significant bit
LTRP long-term reference
picture
LMCS luma mapping with chroma
scaling
MIP matrix-based
intra prediction
MPS most
probable symbol
MSB most
significant bit
MTS multiple
transform selection
MVP motion
vector prediction
NAL network
abstraction layer
OLS output
layer set
OP operation
point
OPI operating
point information
P predictive
PH picture
header
POC picture
order count
PPS picture
parameter set
PROF prediction
refinement with optical flow
PT picture
timing
PU picture
unit
QP quantization
parameter
RADL random
access decodable leading (picture)
RASL random
access skipped leading (picture)
RBSP raw
byte sequence payload
RGB red,
green, and blue
RPL reference
picture list
SAO sample
adaptive offset
SAR sample aspect ratio
SEI supplemental enhancement information
SH slice
header
SLI subpicture
level information
SODB string
of data bits
SPS sequence
parameter set
STRP short-term reference
picture
STSA step-wise temporal sublayer
access
TR truncated
rice
TSRC Transform Skip Residue Coding (TSRC)
VBR variable
bit rate
VCL video
coding layer
VPS video
parameter set
VSEI versatile supplemental enhancement information
(Rec. ITU-T H.274 | ISO/IEC 23002-7)
VUI video
usability information
VVC versatile
video coding (Rec. ITU-T H.266 | ISO/IEC 23090-3)
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