ISO/IEC 29199-2:2020

INTERNATIONAL ISO/IEC
STANDARD 29199-2
Fourth edition
2020-05
Information technology — JPEG XR
image coding system —
Part 2:
Image coding specification
Technologies de l'information — Système de codage d'image JPEG
XR —
Partie 2: Spécification de codage d'image
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
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Contents                                 Page
Foreword …………………………………………………………………………………………………………………………………………………v
Introduction . vi
1 Scope 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 9
5 Conventions . 9
5.6 Adaptive VLC deltaDisc tables . 25
5.7 Adaptive inverse scanning tables . 25
6 General provisions, provisions specified in annexes, and image and codestream structures . 26
6.1 General . 26
6.2 Image planes and component arrays . 26
6.3 Image windowing . 27
6.4 Image partitioning . 27
6.5 Transform coefficients and frequency bands . 28
6.6 Codestream structure . 29
6.7 Precision and word length . 29
7 Overview of decoder . 30
7.1 General . 30
7.2 Overview of parsing process . 31
7.3 Overview of the decoding process . 32
8 Syntax, semantics, and parsing process . 33
8.1 General . 33
8.2 CODED_IMAGE( ) . 34
8.3 IMAGE_HEADER( ) . 35
8.4 IMAGE_PLANE_HEADER( ) . 45
8.5 INDEX_TABLE_TILES( ) . 53
8.6 PROFILE_LEVEL_INFO( ) . 54
8.7 CODED_TILES( ) . 55
8.8 Adaptive VLC code table selection . 87
8.9 Adaptation of CBPLP state variables . 94
8.10 Adaptive CBPHP prediction . 95
8.11 Adaptive inverse scanning . 96

© ISO/IEC 2020 – All rights reserved
iii
8.12 Adaptive coefficient normalization . 99
9 Decoding process. 101
9.1 General . 101
9.2 Image decoding . 101
9.3 Image plane decoding . 102
9.4 Tile transform coefficient processing . 102
9.5 Coefficient remapping . 104
9.6 Transform coefficient prediction . 106
9.7 Derivation of quantization parameters . 115
9.8 Dequantization . 118
9.9 Sample reconstruction . 121
9.10 Output formatting. 152
Annex A (normative) Tag-based file format . 167
Annex B (normative) Profiles and levels . 195
Annex C (informative) Colour imagery representation and colour management . 199
Annex D (informative) Encoder processing . 202
Annex E (normative) Media type specification for the Annex A tag-based file format . 217
Annex F (normative) Storage in the ISO/IEC 23008-12 image file format and associated media type
registrations . 219
Bibliography . 227

© ISO/IEC 2020 – All rights reserved
iv
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
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ISO and IEC technical committees collaborate in fields of mutual interest. Other international
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different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Details of any patent rights identified during the development of the document will be in the
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see www.iso.org/iso/foreword.html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information, in collaboration
with ITU-T. The technically identical text is published as Rec. ITU-T T.832.
This fourth edition cancels and replaces the third edition (ISO/IEC 29199-2:2012), which has been
technically revised. It also incorporates the Amendment ISO/IEC 29199-2:2012/Amd.1:2017.
The main changes compared to the previous edition include:
  the specification of additional colour type identifiers;
  the specification of an alternative file storage format based on ISO/IEC 23008-12 for the storage
and interchange of JPEG XR coded images and image sequences;
  the specification of media type identifiers for use for use in various internet protocols.
A list of all parts in the ISO/IEC 29199 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

© ISO/IEC 2020 – All rights reserved
v
Introduction
This document specifies requirements and implementation guidelines for the compressed representation of
digital images for storage and interchange in a form referred to as JPEG XR. The JPEG XR design provides a
practical coding technology for a broad range of applications with excellent compression capability and important
additional functionalities. An input image is typically operated on by an encoder to create a JPEG XR coded image.
The decoder then operates on the coded image to produce an output image that is either an exact or approximate
reconstruction of the input image.
The primary intended application of JPEG XR is the representation of continuous-tone still images such as
photographic images. The manner of representation of the compressed image data and the associated decoding
process are specified. These processes and representations are generic, that is, they are applicable to a broad
range of applications using compressed colour and grayscale images in communications and computer systems
and within embedded applications, including mobile devices.
As of 2008, the most widely used digital photography format is a nominal implementation of the first JPEG coding
format as specified in ITU-T Recommendation T.81 | ISO/IEC 10918-1. This encoding uses a bit depth of 8 for each
of three channels, resulting in 256 representable values per channel (a total of 16 777 216 representable colour
values).
More demanding applications may require a bit depth of 16, providing 65 536 representable values for each
colour values. Additional scenarios may necessitate even greater bit
channel, and resulting in over 2.8 * 10
depths and sample representation formats. When memory or processing power is at a premium, as few as five or
six bits per channel may be used.
The JPEG XR specification enables greater effective use of compressed imagery with this broadened diversity of
application requirements. JPEG XR supports a wide range of colour encoding formats including monochrome, RGB,
CMYK and n-component encodings using a variety of unsigned integer, fixed point, and floating point decoded
numerical representations with a variety of bit depths. The primary goal is to provide a compressed format
specification appropriate for a wide range of applications while keeping the implementation requirements for
encoders and decoders simple. A special focus of the design is support for emerging high dynamic range (HDR)
imagery applications.
JPEG XR combines the benefits of optimized image quality and compression efficiency together with low-
complexity encoding and decoding implementation requirements. It also provides an extensive set of additional
functionalities, including:
 high compression capability;
 low computational and memory resource requirements;
 lossless and lossy compression;
 image tile segmentation for random access and large image formats;
 support for low-complexity compressed-domain image manipulations;
 support for embedded thumbnail images and progressive resolution refinement;
 embedded codestream scalability for both image resolution and fidelity;
 alpha plane support;
 bit-exact decoder results for fixed and floating point image formats.

© ISO/IEC 2020 – All rights reserved
vi
Important detailed design properties include:
 high performance, embedded system friendly compression;
 small memory footprint;
 integer-only operations with no divides;
 a signal processing structure that is highly amenable to parallel processing;
 use of the same signal processing operations for both lossless and lossy compression operation;
 support for a wide range of decoded sample formats (many of which support high dynamic range imagery):
 monochrome, RGB, CMYK or n-component image representation;
 8- or 16-bit unsigned integer;
 16- or 32-bit fixed point;
 16- or 32-bit floating point;
 several packed bit formats;
 1-bit per sample monochrome;
 5- or 10-bit per sample RGB;
 radiance RGBE.
The algorithm uses a reversible hierarchical lifting-based lapped biorthogonal transform. The transform has
lossless image representation capability and requires only a small number of integer processing operations for
both encoding and decoding. The processing is based on 16 × 16 macroblocks in the transform domain, which may
or may not affect overlapping areas in the spatial domain (with the overlapping property selected under the
control of the encoder). The design provides encoding and decoding with a minimal memory footprint suitable for
embedded implementations.
The algorithm provides native support for both RGB and CMYK colour types by converting these colour formats to
an internal luma-dominant format through the use of a reversible colour transform. In addition, YUV,
monochrome and arbitrary n-channel colour formats are supported.
The transforms employed are reversible; both lossless and lossy operations are supported using the same
algorithm. Using the same algorithm for both types of operation simplifies implementation, which is especially
important for embedded applications.
A wide range of numerical encodings at multiple bit depths are supported: 8-bit and 16-bit formats, as well as
additional specialized packed bit formats, are supported for both lossy and lossless compression. (32-bit formats
are supported using lossy compression.) Up to 24 bits are retained through the various transforms. While only
integer arithmetic is used for internal processing, lossless and lossy coding are supported for floating point and
fixed point image data – as well as for integer image formats.
The main body of this document specifies the syntax and semantics of JPEG XR coded images and the associated
decoding process that produces an output image from a coded image. Annex A specifies a tag-based file storage
format for storage and interchange of such coded images. Annex B specifies profiles and levels, which determine
conformance requirements for classes of encoders and decoders. Aspects of colour imagery representations and
colour management are discussed in Annex C. The typical expected encoding process is described in Annex D.
Annex E contains a media type specification for images encoded according to the tag-based format specified in
Annex A for use in various internet protocols. Annex F specifies an alternative file storage format based on

© ISO/IEC 2020 – All rights reserved
vii
ISO/IEC 23008-12 and associated media type specifications for the storage and interchange of JPEG XR coded
images and image sequences. Annexes A, B, E, and F are an integral part of this document and contain normative
specifications.
The International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC)
draw attention to the fact that it is claimed that compliance with this document may involve the use of patents.
ISO and IEC take no position concerning the evidence, validity and scope of these patent rights.
The holders of these patent rights have assured ISO and IEC that they are willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect,
the statements of the holders of these patent rights are registered with ISO and IEC. Information may be obtained
.
from the patent database available at www.iso.org/patents
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those in the patent database. ISO and IEC shall not be held responsible for identifying any or all
such patent rights.
© ISO/IEC 2020 – All rights reserved
viii
INTERNATIONAL STANDARD ISO/IEC 29199-2:2020(E)

Information technology — JPEG XR image coding system —
Part 2:
Image coding specification
1 Scope
This document specifies a coding format, referred to as JPEG XR, which is designed primarily for continuous-tone
photographic content.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references, the
latest edition of the referenced document (including any amendments) applies.
Rec. ITU-T T.833 | ISO/IEC 29199-3, Information technology — JPEG XR image coding system — Part 3: Motion
JPEG XR
ISO/IEC/IEEE 60559, Information technology — Microprocessor systems — Floating-Point arithmetic
ISO/IEC 10646:2017, Information technology — Universal coded character set (UCS)
ISO/IEC 23008-12:2017, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 12: Image file format
3 Terms and definitions
For the purposes of this document, the terms, definitions and abbreviated terms specified in ISO/IEC 23008-12
and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
 ISO Online browsing platform: available at https://www.iso.org/obp
 IEC Electropedia: available at http://www.electropedia.org/
NOTE For the avoidance of doubt, in case of ambiguities, the definitions in this document take precedence over the
definitions of ISO/IEC 23008-12 except in regard to the file format specified in Annex F. A sample in the context of ISO/IEC
23008-12 and in Annex F is "all the data associated with a single time". In Annex G, this is meant as all data associated with one
coded image, not "element in a two-dimensional image array that comprises an image plane".
3.1
adaptive coefficient normalization
parsing sub-process where transform coefficients (3.75) are dynamically partitioned into a VLC-coded (3.77) part
and a fixed-length coded (3.28) part, in a manner designed to control (i.e., "normalize") bits used to represent the
VLC-coded part
Note 1 to entry: The fixed-length coded part of DC coefficients and low-pass coefficients is called FLC refinement and the fixed-
length coded part of high-pass coefficients is called flexbits.

© ISO/IEC 2020 – All rights reserved
3.2
adaptive inverse scanning
parsing sub-process where the zigzag scan order (3.80) associated with a set of transform coefficients (3.75) is
dynamically modified, based on the statistics of previously-parsed transform coefficients
3.3
adaptive VLC
parsing sub-process where the code table associated with VLC (3.77) parsing of a particular syntax element is
switched, among a finite set of fixed tables, based on the statistics of previously-parsed instances of this syntax
element
3.4
alpha image plane
optional secondary image plane (3.36) associated with an image of the same dimensions as the luma (3.45)
component of the primary image plane (3.57)
Note 1 to entry: The alpha image plane has one component, a luma component.
3.5
block
m×n array of samples (3.64), or an m×n array of transform coefficients (3.75)
3.6
block index
integer in the range 0 to 15 identifying, by its position in raster scan order (3.61), a particular 4×4 block (3.5)
within a partition of a 16×16 block into 16 4×4 blocks
3.7
byte
sequence of 8 bits
3.8
byte-aligned
bit in a codestream (3.13) where its position is an integer multiple of 8 bits from the beginning of the codestream,
where the first bit in the codestream is at position 0
3.9
chroma
component (3.14) of the primary image plane (3.57) with non-zero index, or the transform coefficients (3.75) and
sample values associated with this component
3.10
coded block pattern high-pass
syntax element indicating the coded block status (3.12), i.e. the presence or absence of non-zero high-pass
coefficients (3.34), for each of the blocks (3.5) in the macroblock (3.46)
3.11
coded block pattern low-pass
syntax element indicating the presence or absence of non-zero low-pass coefficients (3.44) in the macroblock
(3.46)
3.12
coded block status
indication of the presence or absence of non-zero transform coefficients (3.75) in that block (3.5)
3.13
codestream
sequence of bits contained in a sequence of bytes (3.7) from which syntax elements are parsed

© ISO/IEC 2020 – All rights reserved
Note 1 to entry: The most significant bit of the first byte is the first bit of the codestream, the next most significant bit of the
first byte is the second bit of the codestream, and so on, to the least significant bit of the first byte (which is the eighth bit of the
codestream), followed by the most significant bit of the second byte (which is the ninth bit of the codestream), and so on, up to
and including the least significant bit of the last byte of the sequence of bytes (which is the last bit of the codestream).
3.14
component
array of samples associated with an image plane (3.36)
3.15
context
possible value of a specific instance of a context variable (3.16)
3.16
context variable
variable used in the parsing process (3.54) to select which data structure is to be used for the adaptive VLC (3.3)
parsing of a given syntax element
3.17
DC coefficient
first subset when the transform coefficients (3.75), that are contained in a specific macroblock (3.46) and a specific
component (3.14), are partitioned into 3 subsets
3.18
DC-LP array
array of all DC (3.17) and low-pass (3.44) transform coefficients (3.75), for all macroblocks (3.46) associated with a
specific component (3.14)
3.19
decoder
embodiment of a parsing process (3.54) and decoding process (3.20)
3.20
decoding process
process of computing output sample values from the parsed syntax elements of the codestream (3.13)
3.21
dequantization
process of rescaling the quantized transform coefficients (3.75) after their value has been parsed from the
codestream (3.13) and before they are presented to the inverse transform process (3.41)
3.22
discriminant
one of DiscrimVal1 or DiscrimVal2, which are the two member variables of an instance of the adaptive VLC (3.3)
data structure
Note 1 to entry: The adaptive VLC data structure is specified in subclause 5.5.5.
3.23
encoder
embodiment of an encoding process (3.24)
3.24
encoding process
process of converting source sample values into a codestream (3.13)

© ISO/IEC 2019 – All rights reserved
3.25
extended image
image (3.35) produced by the decoding process (3.20) prior to windowing (3.79)
Note 1 to entry: The extended image has a luma (3.45) array that is an integer multiple of 16 in width and height.
3.26
file
finite-length sequence of bytes (3.7) that is accessible to a decoder (3.19) in a manner such that the decoder can
obtain access to the data at specified positions within the sequence of bytes
EXAMPLE Access to the data can be achieved by storing the entire sequence of bytes in random access memory or by
performing "position seek" operations to specified positions within the sequence of bytes.
3.27
file format
specified structure for the content of a file (3.26)
3.28
fixed-length code
FLC
code which assigns a finite set of allowable bit patterns to a specific set of values, where each bit pattern has the
same length
3.29
FLC refinement
fixed-length coded (3.28) part of a DC coefficient (3.17) or low-pass coefficient (3.44) that is parsed using adaptive
fixed-length codes
3.30
flexbits
fixed-length coded (3.28) part of the high-pass coefficient (3.34) information which is parsed using adaptive fixed-
length codes
3.31
frequency band
one of three subsets of the transform coefficients (3.75) for an image (3.35), which are separately parsed: DC
coefficients (3.17), low-pass coefficients (3.44) and high-pass coefficients (3.34)
3.32
frequency mode
codestream (3.13) structure mode where the DC (3.17), low-pass (3.44), high-pass (3.34) and flexbits (3.30)
frequency bands (3.31) for each tile (3.72) are grouped separately
3.33
hard tiles
codestream (3.13) structure mode where the overlap operators are not applied across tile boundaries; instead,
boundary overlap operators are applied at tile boundaries
3.34
high-pass coefficient
third subset, when the transform coefficients (3.75) that are contained in a specific macroblock (3.46) and a
specific component (3.14) are partitioned into 3 subsets
3.35
image
result of the decoding process (3.20) consisting of a primary image plane (3.57) and an optional alpha image plane
(3.4)
© ISO/IEC 2020 – All rights reserved
3.36
image plane
collective term for a grouping of the components (3.14) of the image (3.35)
3.37
initial level value
one of two values used to compute the VLC-coded (3.77) part of a transform coefficient (3.75)
3.38
interleaved alpha image plane
alpha image plane (3.4) that is coded in a codestream (3.13) in an interleaved manner together with the primary
image plane (3.57)
3.39
internal colour format
colour format associated with the spatial-domain samples obtained through the inverse transform process (3.40)
and the sample reconstruction process (3.65), and distinguished from the output colour format (3.49) associated
with the output formatting process (3.50)
3.40
inverse core transform
ICT
two steps of the inverse transform process (3.40) that involve processing of transform coefficients (3.75) associated
with each macroblock (3.46) independently, with no overlap filtering (3.53)
3.41
inverse transform process
part of the decoding process (3.20) by which a set of dequantized (3.21) transform coefficients (3.75) are converted
into spatial-domain values
3.42
inverse scanning
process of reordering an ordered set of parsed syntax elements from the codestream (3.13) to form an array of
transform coefficients (3.75) associated with a specific component (3.14) and macroblock (3.46)
3.43
little-endian form
ordering of the bytes (3.7) that represent a numerical value as an integer number of bytes in which the bytes
representing the number are in ascending order of significance
Note 1 to entry: With the least significant byte first, followed by the next least significant byte, etc.
3.44
low-pass coefficient
second subset, when the transform coefficients (3.75) that are contained in a specific macroblock (3.46) and a
specific component (3.14) are partitioned into 3 subsets
3.45
luma
component (3.14) of an image plane (3.36) with index zero, and the transform coefficients (3.75) and sample values
associated with this component
Note 1 to entry: Although this term is commonly associated with a signal that conveys perceptual brightness information, as
used in this document the term is primarily an identifier of a particular array of samples or transform coefficients for an image
(3.35).
© ISO/IEC 2019 – All rights reserved
3.46
macroblock
collection of transform coefficients (3.75) or samples, across all components (3.14), that have the same indices i
and j with respect to a macroblock partition (3.47)
3.47
macroblock partition
partitioning of each component (3.14), into 16×16, 8×8, or 16×8 blocks (3.5), depending on the internal colour
format (3.39)
3.48
output bit depth
representation, including the number of bits and the interpretation of the bit pattern, used for the sample values
of the output image (3.35) that are the result of the decoding process (3.20)
3.49
output colour format
colour format associated with the output image (3.35) that is the result of the decoding process (3.20)
3.50
output formatting process
process of converting the arrays of samples (that are the result of the sample reconstruction process (3.65)) into
the output samples that constitute the output of the decoding process (3.20)
Note 1 to entry: This specifies a conversion (if necessary) into the appropriate output colour format (3.49) and output bit depth
(3.48).
3.51
output image height
height of the sub-array of the luma (3.45) component (3.14) of the primary image plane (3.57) that is output by the
decoding process (3.20)
3.52
output image width
width of the sub-array, of the luma (3.45) component (3.14) of the primary image plane (3.57) that is output by the
decoding process (3.20)
3.53
overlap filtering
steps of the inverse transform process (3.41) that involve processing of transform coefficients (3.75) across
adjacent blocks (3.5) and macroblocks (3.46)
Note 1 to entry: When overlap filtering is applied, it is applied across macroblock boundaries as well as block boundaries.
When the codestream (3.13) uses soft tiles (3.67), the overlap filtering is also applied across tile (3.72) boundaries. Otherwise,
overlap filtering does not occur across tile boundaries.
3.54
parsing process
process of extracting bit sequences from the codestream (3.13), converting these bit sequences to syntax element
values, and setting the values of global variables for use in the decoding process (3.20)
3.55
prediction
process of computing an estimate of the sample value or data element that is currently being decoded
3.56
prediction residual
difference between the result of the prediction (3.55) process invoked for a sample or data element, and its
intended value
© ISO/IEC 2020 – All rights reserved
3.57
primary image plane
image plane (3.36) that consists of all image (3.35) components (3.14) that are not a part of the alpha image plane
(3.4)
3.58
QP index
integer, which for a particular frequency band (3.31) and macroblock (3.46) specifies the index into the table of
quantization parameters (3.60) available for this frequency band and tile (3.72)
Note 1 to entry: The QP index (3.58) thereby selects, for this macroblock, the quantization parameter used for the
dequantization (3.21) of the transform coefficients (3.75) in the specific frequency band (3.31).
3.59
QP set
set of quantization parameters (3.60) associated with a particular frequency band (3.31), corresponding to the
luma (3.45) and chroma (3.9) components (3.14)
3.60
quantization parameter
QP
value used to compute the scaling factor for the dequantization (3.21) of a transform coefficient (3.75), before the
inverse transform process (3.41) is applied
3.61
raster scan order
scan order in which a two-dimensional array of values is scanned row-wise from left to right, and the rows are
scanned from the top row to the bottom
3.62
refinement
process of modifying a predicted or partially-computed transform coefficient (3.75)
3.63
run
number of zero valued coefficient levels that precede a non-zero valued coefficient level in the zigzag scan order
(3.80) during the inverse scanning (3.42) process
3.64
sample
element in a two-dimensional image array that comprises an image plane (3.36)
3.65
sample reconstruction process
process of converting dequantized (3.21) transform coefficients (3.75) into samples of the image (3.35)
3.66
separate alpha image plane
alpha image plane (3.4) that is coded in a codestream separately from the primary image plane (3.57)
3.67
soft tiles
codestream (3.13) structure mode where the overlap operators are applied across tile boundaries
3.68
spatial co-location
sub-arrays of samples are spatially co-located (3.68) across components (3.14) when they correspond to the same
spatial region of the decoded image (3.35)

© ISO/IEC 2019 – All rights reserved
Note 1 to entry: The macroblock partition (3.47) of the image ensures that the i-th macroblock (3.46) horizontally and j-th
macroblock vertically across all components are spatially co-located.
3.69
spatial mode
codestream (3.13) structure mode where the DC (3.17), low-pass (3.44), high-pass (3.34) and flexbits (3.30)
frequency bands (3.31) for each specific macroblock (3.46) are grouped together
3.70
spatial transformation
element in the codestream (3.13) indicating the preferred final displayed orientation of the decoded image (3.35)
Note 1 to entry: As specified in subclause 8.3.8.
Note 2 to entry: The spatial transformation (3.70) is only a suggestion, and decoder (3.19) conformance is checked only for the
decoded image (3.35) prior to the application of this transformation (i.e. for orientation 0).
3.71
start code
bit pattern that specifies the beginning of a tile packet (3.73) or other distinguished, contiguous set of syntax
elements in the codestream (3.13)
3.72
tile
collection of macroblocks (3.46) that have the same indices i and j with respect to a tile partition (3.74)
Note 1 to entry: Each tile (3.72) corresponds to the macroblocks for a rectangular region of the image (3.35).
3.73
tile packet
contiguous subset of the codestream (3.13), which contains the coded syntax elements associated with a specific
tile (3.72)
3.74
tile partition
partition of the image (3.35) into rectangular arrays of macroblocks (3.46)
Note 1 to entry: As specified in subclause 6.4.
3.75
transform coefficient
values, associated with each specific macroblock (3.46) and specific component (3.14), that – after dequantization
(3.21) – form the input arrays into the inverse transform process (3.41)
3.76
universal multiple-octet coded character set transformation format 8
UTF-8
8-bit character set encoding
Note 1 to entry: As specified in ISO/IEC 10646:2017, Annex D.
3.77
variable-length code
VLC
code which assigns a finite set of allowable bit patterns to a specific set of values, where each bit pattern is
potentially of a different length

© ISO/IEC 2020 – All rights reserved
3.78
VLC refinement
one of two values used to compute the VLC-coded (3.76) part of a transform coefficient (3.75)
Note 1 to entry: The number of bits required to specify the VLC-refinement is dependent on the value of the initial level value
(3.37). The VLC refinement is added to the initial level value to produce the VLC-coded part of the transform coefficient.
3.79
windowing
selection of spatially co-located (3.68) sub-arrays of the components (3.14) of all present image planes (3.36)
associated with an image (3.35) that are output by the decoding process (3.20)
3.80
zigzag scan order
adaptive ordering for the inverse scanning (3.42) process, which assigns array indices to each subsequent
transform coefficient (3.75) parsed from the codestream (3.13)
4 Abbreviated terms
CBPHP coded block pattern high-pass
CBPLP coded block pattern low-pass
CIE International Commission on Illumination
FCC Federal Communications Commission
FCT forward core transform
FLC fixed-length code
HP high-pass
ICC International Color Consortium
ICT inverse core transform
JPEG Joint Photographic Experts Group
LP low-pass
LSB least significant bit
MSB most significant bit
NTSC National Television System Committee
QP quantization parameter
RP recommended practice
SMPTE Society of Motion Picture and Television Engineers
UUID universal unique identifier (as specified by ISO/IEC 11578)
UTF universal multiple-octet coded character set transformation format (as specified by ISO/IEC 10646)
VLC variable-length code
5 Conventions
5.1 Conformance language
The keyword "reserved" indicates a provision that is not specified at this time, shall not be used in
implementations conforming to this edition of this document and may be specified in the future. The keyword
"forbidden" indicates "reserved" and in addition indicates that the provision will never be specified in the future.

© ISO/IEC 2019 – All rights reserved
5.2 Operators
NOTE Many of the operators used in this document are similar to those used in the C programming language (e.g. as
specified in ISO/IEC 9899).
5.2.1 Arithmetic operators
+ addition
− subtraction (as a binary operator) or negation (as a unary prefix operator)
++ increment by one as a unary postfix operator
− − decrement by one as a unary postfix operator
* multiplication
/ integer division, where the result is truncated towards zero
÷ division in mathematical equations where no truncation or rounding is intended
x division in mathematical equations where no truncation or rounding is intended

y
% x % a is defined as the modulus operator for x >= 0 and a > 0
x % a is defined as −(((−x) % a)) for x < 0 and a > 0
NOTE 1 Although sometimes used as unary prefix operators in the C programming language, the "++" and "− −" arithmetic
operators are not used as unary prefix operators in this document.
NOTE 2 The division operators used in this document differ somewhat from those used in the C programming language.
5.2.2 Logical operators
| | logical OR
&& logical AND
! logical NOT
TRUE/FALSE convention:
 When a variable or arithmetic expression having a non-zero value is evaluated as a logical condition or as an
element of a logical expression, it is evaluated as TRUE, and when a variable or expression having a zero value
is evaluated as a logical condition or as an element of a logical expression, it is evaluated as FALSE.
 When the value of a variable or arithmetic expression is compared to the value TRUE (in text or using a
relational operator), it is compared to the value 1, and when the value of a variable or arithmetic expression is
compared to the value FALSE (in text or using a relational operator), it is compared to the value 0.
 When a variable is set to the value TRUE, it is set to the value 1; and when a variable is set to the value FALSE,
it is set to the value 0.
© ISO/IEC 2020 – All rights reserved
5.2.3 Relational operators
> greater than
>= greater than or equal to
< less than
<= less than or equal to
= = equal to
!= not equal to
5.2.4 Bit-wise operators
Bit-wise operators operate on bit pattern values that are produced by conversion of an integer value to an
equivalent bit pattern value. Bit-wise operators operate on a two's complement representation of the integer
value using a number of bits sufficient to represent the integer value (with a bit equal to 0 in the MSB of non-
negative integer value representations and otherwise with a bit equal to 1 in the MSB). The result of a bit-wise
operator is then interpreted as a two's complement representation of an integer value. The following bit-wise
operators are defined:
& AND
When operating on a bit pattern argument that contains fewer bits than the other argument, the shorter
argument is extended by adding more significant bits equal to the MSB of the shorter argument such
that the number of bits representing the shorter argument is made the same as the number of bits for
the longer argument.
| OR
When operating on a bit pattern argument that contains fewer bits than the other argument, the shorter
argument is extended by adding more significant bits equal to the MSB of the shorter argument such
that the number of bits representing the shorter argument is made the same as the number of bits for
the longer argument.
^ XOR
When operating on a bit pattern
...