VVC常用术语
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来源：JVET-L0628
3.1 access unit: 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.
3.2 AC transform coefficient: Any transform coefficient for which the frequency index in at least one of the two
dimensions is non-zero.
3.3 bin: One bit of a bin string.
3.4 binarization: A set of bin strings for all possible values of a syntax element.
3.5 binarization process: A unique mapping process of all possible values of a syntax element onto a set of bin
strings.
3.6 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.
3.7 bin string: An intermediate binary representation of values of syntax elements from the binarization of the syntax
element.
3.8 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.
3.9 bitstream: A sequence of bits, in the form of a NAL unit stream or a byte stream, that forms the representation
of coded pictures and associated data forming one or more coded video sequences (CVSs).
ISO/IEC VVC
2 ITU-T Rec. H.VVC
3.10 block: An MxN (M-column by N-row) array of samples, or an MxN array of transform coefficients.
3.11 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.
3.12 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.
3.13 byte stream: An encapsulation of a NAL unit stream containing start code prefixes and NAL units as specified
in Annex TBD.
3.14 can: A term used to refer to behaviour that is allowed, but not necessarily required.
3.15 chroma: An adjective, represented by the symbols Cb and Cr, specifying that a sample array or single sample is
representing one of the two colour difference signals related to the primary colours.
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.
3.16 coded picture: A coded representation of a picture containing all CTUs of the picture.
3.17 coded representation: A data element as represented in its coded form.
3.18 coded video sequence (CVS): A sequence of access units that consists, in decoding order, of an IRAP access
unit, followed by zero or more access units that are not IRAP access units, including all subsequent access units
up to but not including any subsequent access unit that is an IRAP access unit.
3.19 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.
3.20 coding tree block (CTB): An NxN block of samples for some value of N such that the division of a component
into CTBs is a partitioning.
3.21 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 or a picture that is coded using three
separate colour planes and syntax structures used to code the samples.
3.22 coding unit (CU): A coding block of luma samples, two corresponding coding blocks of chroma samples of a
picture that has three sample arrays, or a coding block of samples of a monochrome picture or a picture that is
coded using three separate colour planes and syntax structures used to code the samples.
3.23 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.
3.24 context variable: A variable specified for the adaptive binary arithmetic decoding process of a bin by an
equation containing recently decoded bins.
3.25 decoded picture: A decoded picture is derived by decoding a coded picture.
3.26 decoder: An embodiment of a decoding process.
3.27 decoding order: The order in which syntax elements are processed by the decoding process.
3.28 decoding process: The process specified in this Specification that reads a bitstream and derives decoded pictures
from it.
3.29 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.
3.30 encoder: An embodiment of an encoding process.
3.31 encoding process: A process not specified in this Specification that produces a bitstream conforming to this
Specification.
3.32 flag: A variable or single-bit syntax element that can take one of the two possible values: 0 and 1.
3.33 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.
ISO/IEC VVC
ITU-T Rec. H.VVC 3
3.34 informative: A term used to refer to content provided in this Specification that does not establish any mandatory
requirements for conformance to this Specification and thus is not considered an integral part of this
Specification.
3.35 inter coding: Coding of a coding block, slice, or picture that uses inter prediction.
3.36 inter prediction: A prediction derived in a manner that is dependent on data elements (e.g., sample values or
motion vectors) of one or more reference pictures.
NOTE – A prediction from a reference picture that is the current picture itself is also inter prediction.
3.37 intra coding: Coding of a coding block, slice, or picture that uses intra prediction.
3.38 intra prediction: A prediction derived from only data elements (e.g., sample values) of the same decoded slice
without referring to a reference picture.
3.39 intra random access point (IRAP) access unit: An access unit in which the coded picture is an IRAP picture.
3.40 intra random access point (IRAP) picture: A coded picture for which each VCL NAL unit has nal_unit_type
equal to IRAP_NUT.
3.41 intra (I) slice: A slice that is decoded using intra prediction only.
3.42 leaf: A terminating node of a tree that is a root node of a tree of depth 0.
3.43 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 may, within the specified constraints, support a different
level for each supported profile.
3.44 list 0 (list 1) motion vector: A motion vector associated with a reference index pointing into reference picture
list 0 (list 1).
3.45 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).
3.46 luma: An adjective, represented by the symbol or subscript Y or L, specifying that a sample array or single
sample is representing the monochrome signal related to the primary colours.
NOTE – The term luma is used rather than the term luminance in order to avoid the implication of 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.
3.47 may: A term that is used to refer to behaviour that is allowed, but not necessarily required.
NOTE – In some places where the optional nature of the described behaviour is intended to be emphasized, the phrase
"may or may not" is used to provide emphasis.
3.48 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.
3.49 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 may become parent node for another split into either
two or three child nodes.
3.50 must: A term that is used in expressing an observation about a requirement or an implication of a requirement
that is specified elsewhere in this Specification (used exclusively in an informative context).
3.51 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.
3.52 network abstraction layer (NAL) unit stream: A sequence of NAL units.
3.53 non-IRAP picture: A coded picture for which each VCL NAL unit has nal_unit_type equal to
NON_IRAP_NUT.
3.54 non-VCL NAL unit: A NAL unit that is not a VCL NAL unit.
3.55 note: A term that is used to prefix informative remarks (used exclusively in an informative context).
3.56 output order: The order in which the decoded pictures are output from the decoded picture buffer (for the
decoded pictures that are to be output from the decoded picture buffer).
3.57 parameter: A syntax element of a sequence parameter set (SPS) or picture parameter set (PPS), or the second
word of the defined term quantization parameter.
ISO/IEC VVC
4 ITU-T Rec. H.VVC
3.58 partitioning: The division of a set into subsets such that each element of the set is in exactly one of the subsets.
3.59 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 may be either a frame or a field. However, in one CVS, either all pictures are frames or all pictures
are fields.
3.60 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 slice header.
3.61 picture order count (POC): A variable that is associated with each picture, uniquely identifies the associated
picture among all pictures in the CVS, and, when the associated picture is to be output from the decoded picture
buffer, indicates the position of the associated picture in output order relative to the output order positions of
the other pictures in the same CVS that are to be output from the decoded picture buffer.
3.62 prediction: An embodiment of the prediction process.
3.63 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.
3.64 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.
3.65 predictor: A combination of specified values or previously decoded data elements (e.g., sample value or motion
vector) used in the decoding process of subsequent data elements.
3.66 profile: A specified subset of the syntax of this Specification.
3.67 pulse code modulation (PCM): Coding of the samples of a block by directly representing the sample values
without prediction or application of a transform.
3.68 quadtree: A tree in which a parent node can be split into four child nodes, each of which may become parent
node for another split into four child nodes.
3.69 quantization parameter: A variable used by the decoding process for scaling of transform coefficient levels.
3.70 random access: The act of starting the decoding process for a bitstream at a point other than the beginning of
the stream.
3.71 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.
3.72 raw byte sequence payload (RBSP): A syntax structure containing an integer number of bytes that is
encapsulated in a NAL unit and that is either empty or has the form of a string of data bits containing syntax
elements followed by an RBSP stop bit and zero or more subsequent bits equal to 0.
3.73 raw byte sequence payload (RBSP) stop bit: A bit equal to 1 present within a raw byte sequence payload
(RBSP) after a string of data bits, for which the location of the end within an RBSP can be identified by searching
from the end of the RBSP for the RBSP stop bit, which is the last non-zero bit in the RBSP.
3.74 reference index: An index into a reference picture list.
3.75 reference picture: A picture that is a short-term reference picture.
NOTE – A reference picture contains samples that may be used for inter prediction in the decoding process of
subsequent pictures in decoding order.
3.76 reference picture list: A list of reference pictures that is used for inter prediction of a P or B slice.
NOTE – For the decoding process of a P slice, there is one reference picture list – reference picture list 0. For the
decoding process of a B slice, there are two reference picture lists – reference picture list 0 and reference picture list 1.
3.77 reference picture list 0: The reference picture list used for inter prediction of a P or the first reference picture
list used for inter prediction of a B slice.
3.78 reference picture list 1: The second reference picture list used for inter prediction of a B slice.
3.79 reserved: A term that may be used to specify that some values of a particular syntax element are for future use
by ITU-T | ISO/IEC and shall not be used in bitstreams conforming to this version of this Specification, but may
be used in bitstreams conforming to future extensions of this Specification by ITU-T | ISO/IEC.
3.80 residual: The decoded difference between a prediction of a sample or data element and its decoded value.
ISO/IEC VVC
ITU-T Rec. H.VVC 5
3.81 scaling: The process of multiplying transform coefficient levels by a factor, resulting in transform coefficients.
3.82 sequence parameter set (SPS): A syntax structure containing syntax elements that apply to zero or more entire
CVSs as determined by the content of a syntax element found in the PPS referred to by a syntax element found
in each slice header.
3.83 shall: A term used to express mandatory requirements for conformance to this Specification.
NOTE – When used to express a mandatory constraint on the values of syntax elements or on the results obtained by
operation of the specified decoding process, it is the responsibility of the encoder to ensure that the constraint is fulfilled.
When used in reference to operations performed by the decoding process, any decoding process that produces identical
cropped decoded pictures to those output from the decoding process described in this Specification conforms to the
decoding process requirements of this Specification.
3.84 short-term reference picture: A picture that is marked as "used for short-term reference".
3.85 should: A term used to refer to behaviour of an implementation that is encouraged to be followed under
anticipated ordinary circumstances, but is not a mandatory requirement for conformance to this Specification.
3.86 slice: An integer number of CTUs ordered consecutively in the raster scan and contained in a single NAL unit.
3.87 slice header: A part of a coded slice containing the data elements pertaining to the first or all CTUs represented
in the slice.
3.88 source: A term used to describe the video material or some of its attributes before encoding.
3.89 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.
3.90 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.
3.91 syntax element: An element of data represented in the bitstream.
3.92 syntax structure: Zero or more syntax elements present together in the bitstream in a specified order.
3.93 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.
3.94 transform: A part of the decoding process by which a block of transform coefficients is converted to a block of
spatial-domain values.
3.95 transform block: A rectangular MxN block of samples resulting from a transform in the decoding process.
3.96 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.
3.97 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.
3.98 transform unit (TU): A transform block of luma samples and two corresponding transform blocks of chroma
samples of a picture and syntax structures used to transform the transform block samples.
3.99 tree: A tree is a finite set of nodes with a unique root node.
3.100 unspecified: A term that may be used to specify some values of a particular syntax element to indicate that the
values have no specified meaning in this Specification and will not have a specified meaning in the future as an
integral part of future versions of this Specification.
3.101 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.
