Information technology – General video coding

This document specifies low complexity enhancement video coding.

Technologies de l'information – Codage vidéo général

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Published
Publication Date
31-Oct-2021
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5060 - Close of voting Proof returned by Secretariat
Start Date
10-Aug-2021
Completion Date
09-Aug-2021
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INTERNATIONAL ISO/IEC
STANDARD 23094-2
First edition
2021-11
Information technology – General
video coding —
Part 2:
Low complexity enhancement video
coding
Technologies de l'information – Codage vidéo général —
Partie 2: Codage vidéo d'amélioration de faible complexité
Reference number
ISO/IEC 23094-2:2021(E)
© ISO/IEC 2021
---------------------- Page: 1 ----------------------
ISO/IEC 23094-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO/IEC 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC 23094-2:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 6

5 Conventions ............................................................................................................................................................................................................... 7

5.1 General ........................................................................................................................................................................................................... 7

5.2 Arithmetic operators ........................................................................................................................................................................ 7

5.3 Logical operators .................................................................................................................................................................................. 8

5.4 Relational operators .......................................................................................................................................................................... 8

5.5 Bit-wise operators ............................................................................................................................................................................... 8

5.6 Assignment operators ...................................................................................................................................................................... 9

5.7 Range notation ....................................................................................................................................................................................... 9

5.8 Mathematical functions .................................................................................................................................................................. 9

5.9 Order of operation precedence ............................................................................................................................................. 10

5.10 Variables, syntax elements and tables............................................................................................................................ 11

5.11 Text description of logical operations ............................................................................................................................12

5.12 Processes .................................................................................................................................................................................................. 13

6 Bitstream and picture formats, partitioning, scanning processes and neighbouring

relationships .........................................................................................................................................................................................................13

6.1 Bitstream formats ............................................................................................................................................................................ 13

6.2 Source, decoded and output picture formats ........................................................................................................... 14

6.3 Partitioning of pictures ............................................................................................................................................................... 17

6.3.1 Organization of the hierarchical structure ............................................................................................. 17

6.3.2 Partitioning of residuals plane ........................................................................................................................... 17

7 Syntax and semantics ..................................................................................................................................................................................18

7.1 Method of specifying syntax in tabular form ......... .................................................................................................. 18

7.2 Specification of syntax functions and descriptors .............................................................................................. 19

7.3 Syntax in tabular form .................................................................................................................................................................. 20

7.3.1 Syntax order ........................................................................................................................................................................20

7.3.2 NAL unit and NAL unit header syntax ......................................................................................................... 20

7.3.3 Process block syntax ................................................................................................................................................... 21

7.3.4 Process payload – sequence configuration .............................................................................................. 22

7.3.5 Process payload – global configuration ...................................................................................................... 22

7.3.6 Process payload – picture configuration ................................................................................................... 24

7.3.7 Process payload – encoded data ........................................................................................................................ 25

7.3.8 Process payload – encoded tiled data ........................................................................................................... 26

7.3.9 Process payload – surface .......................................................................................................................................28

7.3.10 Process payload – additional info ....................................................................................................................28

7.3.11 Process payload – filler ..............................................................................................................................................29

7.3.12 Byte alignment syntax ...............................................................................................................................................29

7.4 Semantics ................................................................................................................................................................................................. 29

7.4.1 General .....................................................................................................................................................................................29

7.4.2 NAL unit semantics ....................................................................................................................................................... 30

7.4.3 Data block unit configuration semantics ................................................................................................... 32

8 Decoding process .............................................................................................................................................................................................41

8.1 General decoding process .......................................................................................................................................................... 41

8.2 Payload data block unit process ........................................................................................................................................... 41

8.3 Picture enhancement decoding process ....................................................................................................................... 42

8.3.1 General enhancement decoding process ................................................................................................... 42

8.3.2 Decoding process for picture enhancement encoded data (payload_

encoded_data) .................................................................................................................................................................... 42

iii
© ISO/IEC 2021 – All rights reserved
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ISO/IEC 23094-2:2021(E)
8.3.3 Decoding process for picture enhancement encoded tiled data (payload_

encoded_tiled_data) ..................................................................................................................................................... 45

8.3.4 Decoding process for enhancement sub-layer 1 (L-1) encoded data ................................50

8.3.5 Decoding process for enhancement sub-layer 2 (L-2) encoded data ................................ 52

8.4 Decoding process for the temporal prediction ....................................................................................................... 53

8.4.1 General decoding process for temporal prediction ..........................................................................53

8.4.2 Tiled temporal refresh ...............................................................................................................................................54

8.5 Decoding process for the dequantization ....................................................................................................................54

8.5.1 Decoding process for the dequantization overview ........................................................................54

8.5.2 Scaling process for transform coefficients ..............................................................................................54

8.5.3 Derivation of dequantization offset and stepwidth modifier .................................................55

8.5.4 Derivation of quantization matrix ...................................................................................................................56

8.6 Decoding process for the transform ................................................................................................................................ 59

8.6.1 General upscaling process description .................. ...................................................................................... 59

8.6.2 Transform inputs and outputs, transform types, and residual samples

derivation ...................................................................... .........................................................................................................63

8.6.3 2x2 directional decomposition transform ...............................................................................................64

8.6.4 4x4 directional decomposition transform ...............................................................................................65

8.7 Decoding process for the upscaling ..................................................................................................................................66

8.7.1 Nearest sample upsampler kernel description ....................................................................................66

8.7.2 Bilinear upsampler kernel description ........................................................................................................68

8.7.3 Cubic upsampler kernel description .............................................................................................................. 71

8.7.4 Modified Cubic upsampler kernel description ......................................................................................73

8.7.5 Predicted residual process description .......................................................................................................74

8.7.6 Adaptive Cubic upsampler kernel description ...................................................................................... 75

8.8 Decoding process for the residual reconstruction .............................................................................................. 75

8.8.1 Reconstructed residual of each block derivation ............................................................................... 75

8.8.2 Residual reconstruction for L-1 block .......................................................................................................... 76

8.8.3 Residual reconstruction for L-2 block .......................................................................................................... 76

8.9 Decoding process for the L-1 filter ....................................................................................................................................77

8.9.1 L-1 residual filter overview ...................................................................................................................................77

8.9.2 Decoding process for filtering L-1 block ....................................................................................................77

8.10 Decoding process for base decoder data extraction .......................................................................................... 79

8.11 Decoding process for dither filter ...................................................................................................................................... 79

9 Parsing process ..................................................................................................................................................................................................79

9.1 Parsing process inputs and outputs, process overview ................................................................................. 79

9.1.1 Parsing process for entropy encoded transform coefficients .................................................79

9.1.2 Parsing process for entropy encoded temporal signal coefficient group .....................82

9.2 Prefix Coding decoder ...................................................................................................................................................................83

9.2.1 Prefix Coding decoder description ..................................................................................................................83

9.2.2 Prefix Coding decoder table generation .....................................................................................................84

9.2.3 Prefix Coding decoder for tile data sizes ...................................................................................................88

9.3 RLE decoder ...........................................................................................................................................................................................89

9.3.1 RLE process inputs and outputs ........................................................................................................................89

9.3.2 RLE decoder for coefficient groups ................................................................................................................89

9.3.3 RLE decoder description ..........................................................................................................................................90

9.3.4 RLE decoder for temporal signal coefficient group ......................................................................... 91

9.3.5 RLE decoder for tile entropy_enabled_flag fields............................................................................... 93

9.4 Parsing process for 0-th order Exp-Golomb codes..............................................................................................94

Annex A (normative) Profiles and levels ......................................................................................................................................................96

Annex B (normative) Byte stream format ..................................................................................................................................................98

Annex C (normative) Hypothetical reference decoder ............................................................................................................. 101

Annex D (normative) Supplemental enhancement information ..................................................................................... 108

Annex E (normative) Video usability information ......................................................................................................................... 115

Bibliography ..........................................................................................................................................................................................................................119

© ISO/IEC 2021 – All rights reserved
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ISO/IEC 23094-2:2021(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical

activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international

organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the

work.

The procedures used to develop this document and those intended for its further maintenance

are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria

needed for the 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 or

www.iec.ch/members_experts/refdocs).

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

Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC

list of patent declarations received (see patents.iec.ch).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.

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.

A list of all parts in the ISO/IEC 23094 series can be found on the ISO and IEC websites.

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 and

www.iec.ch/national-committees.
© ISO/IEC 2021 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO/IEC 23094-2:2021(E)
Information technology – General video coding —
Part 2:
Low complexity enhancement video coding
1 Scope
This document specifies low complexity enhancement video coding.
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.

ISO/IEC 11578:1996, Information technology — Open systems interconnection — Remote procedure call

(RPC)

ITU-T H.273 | ISO/IEC 23091-2:2019, Information technology — Coding-independent code points — Part

2: Video

ITU-T Recommendation T.35:2000, Procedure for the allocation of ITU-T defined codes for non-standard

facilities
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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 https:// www .electropedia .org/
3.1
access unit

set of NAL units (3.35) that are associated with a particular output time, are consecutive in decoding

order (3.20), and contain exactly one coded picture (3.9)
3.2
bitstream

sequence of bits, in the form of a NAL unit stream (3.36) or a byte stream (3.6), that forms the

representation of coded pictures (3.9), and associated data forming one or more coded video sequences

(CVSs)
3.3
block

MxN (M-column by N-row) array of samples, or an MxN array of transform coefficients (3.57)

3.4
byte

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
© ISO/IEC 2021 – All rights reserved
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ISO/IEC 23094-2:2021(E)
3.5
byte-aligned

position in a bitstream (3.2) in which the position is an integer multiple of 8 bits from the position of the

first bit in the bitstream

Note 1 to entry: A bit, byte (3.4) or syntax element (3.53) is said to be byte-aligned when the position at which it

appears in a bitstream (3.2) is byte-aligned.
3.6
byte stream

encapsulation of a NAL unit stream (3.36) containing start code prefixes (3.51) and NAL units (3.35)

3.7
chroma

sample array or single sample is representing one of the two colour difference signals related to the

primary colours, represented by the symbols Cb and Cr

Note 1 to entry: 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.

3.8
chunk

entropy coded portion of data containing the quantized transform coefficient (3.57) belonging to a

coefficient group
3.9
coded picture

coded representation (3.10) of a picture (3.40) containing all TUs (3.58) of the picture

3.10
coded representation
data element as represented in its coded form
3.11
coded video sequence
CVS
coded sequence of access units (3.1)
3.12
coding block
MxN block (3.3) of samples for some values of M and N
3.13
coding unit

32 x 32 block (3.3) of samples resulting from the parsing of the entropy encoded transform coefficients

(3.57) in the decoding process (3.22)
3.14
coefficient group

syntactical structure containing coded data related to a specific set of transform coefficients (3.57)

3.15
component

array or single sample from one of the three arrays (luma (3.34) and two chroma (3.7)) that compose

a picture (3.40) 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
© ISO/IEC 2021 – All rights reserved
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ISO/IEC 23094-2:2021(E)
3.16
data block
syntax structure (3.54) containing bytes (3.4) corresponding to a type of data
3.17
decoded base picture

decoded picture (3.18) derived by decoding a coded picture (3.9) with a base decoder (3.20)

3.18
decoded picture

picture (3.40) derived by decoding a coded picture (3.9), and which is either a decoded frame (3.29) or a

decoded field (3.28)
3.19
decoded picture buffer
DPB
buffer holding decoded pictures (3.18) for reference or output reordering
3.20
decoder
embodiment of a decoding process (3.22)
3.21
decoding order

order in which syntax elements (3.53) are processed by the decoding process (3.22)

3.22
decoding process

process specified that reads a bitstream (3.2) and derives decoded pictures (3.18) from it

3.23
emulation prevention byte

byte (3.4) equal to 0x03 that may be present within a NAL unit (3.35), the presence of which ensures that

no sequence of consecutive byte-aligned (3.5) bytes in the NAL unit contains a start code prefix (3.51)

3.24
encoder
embodiment of an encoding process (3.25)
3.25
encoding process
process that produces a bitstream (3.2) conforming to this document
3.26
enhancement layer
layer (3.32) within the bitstream (3.2) pertaining to the residual planes (3.47)
3.27
enhancement sub-layer
layer (3.32) of the enhancement layer (3.26)
3.28
field
assembly of alternate rows of a frame (3.29)
3.29
frame

array of luma (3.34) samples in monochrome format or array of luma samples and two corresponding

arrays of chroma (3.7) samples in 4:2:0, 4:2:2, and 4:4:4 colour format, and which consists of two fields

(3.28): a top field and a bottom field
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ISO/IEC 23094-2:2021(E)
3.30
instantaneous decoding refresh picture
IDR picture

picture (3.40) for which a NAL unit (3.35) contains a global configuration data block and does not

refer to any other picture for operation of the decoding process (3.22) of this picture and for which no

subsequent pictures in decoding order (3.21) refer to any picture that precedes it in decoding order

Note 1 to entry: An IDR picture shall occur at least when an IDR picture for the base decoder (3.20) occurs. The

IDR picture for a base decoder is not specified in this document.
3.31
inverse transform

part of the decoding process (3.22) by which a set of transform coefficients (3.57) is converted into

residuals (3.46)
3.32
layer

one of a set of syntactical structures in a non-branching hierarchical relationship

3.33
level

defined set of constraints on the values that may be taken by the syntax elements (3.53) and variables of

this document

Note 1 to entry: The same set of levels is defined for all profiles (3.41), with most aspects of the definition of each

level being in common across different profiles. Individual implementations may, within specified constraints,

support a different level for each supported profile.
3.34
luma

sample array or single sample representing the monochrome signal related to the primary colours,

represented by the symbol or subscript Y or L

Note 1 to entry: 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.

3.35
network abstraction layer unit
NAL unit

syntax structure (3.54) containing an indication of the type of data to follow and bytes (3.4) containing

that data in the form of an RBSP (3.42) interspersed as necessary with emulation prevention bytes (3.23)

3.36
network abstraction layer unit stream
NAL unit stream
sequence of NAL units (3.35)
3.37
output order

order in which the decoded pictures (3.18) are output from the decoded picture buffer (3.19) (for the

decoded pictures that are to be output from the decoded picture buffer)
3.38
partitioning

division of a set into subsets such that each element of the set is in exactly one of the subsets

3.39
plane
collection of data related to plane Y (luma (3.34)) or C (chroma (3.7))
© ISO/IEC 2021 – All rights rese
...

FINAL
INTERNATIONAL ISO/IEC
DRAFT
STANDARD FDIS
23094-2
ISO/IEC JTC 1/SC 29
Information technology – General
Secretariat: JISC
video coding —
Voting begins on:
2021-06-14
Part 2:
Voting terminates on:
Low complexity enhancement video
2021-08-09
coding
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/IEC FDIS 23094-2:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO/IEC 2021
---------------------- Page: 1 ----------------------
ISO/IEC FDIS 23094-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/IEC FDIS 23094-2:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviated terms .............................................................................................................................................................................................. 7

5 Conventions ............................................................................................................................................................................................................... 7

5.1 General ........................................................................................................................................................................................................... 7

5.2 Arithmetic operators ......................................................................................................................................................................... 7

5.3 Logical operators .................................................................................................................................................................................. 8

5.4 Relational operators ........................................................................................................................................................................... 8

5.5 Bit-wise operators................................................................................................................................................................................ 9

5.6 Assignment operators ....................................................................................................................................................................... 9

5.7 Range notation ........................................................................................................................................................................................ 9

5.8 Mathematical functions ................................................................................................................................................................10

5.9 Order of operation precedence ..............................................................................................................................................10

5.10 Variables, syntax elements and tables .............................................................................................................................11

5.11 Text description of logical operations ..............................................................................................................................12

5.12 Processes ...................................................................................................................................................................................................13

6 Bitstream and picture formats, partitioning, scanning processes and neighbouring

relationships ..........................................................................................................................................................................................................14

6.1 Bitstream formats..............................................................................................................................................................................14

6.2 Source, decoded and output picture formats ............................................................................................................14

6.3 Partitioning of pictures .................................................................................................................................................................17

6.3.1 Organisation of the hierarchical structure .............................................................................................17

6.3.2 Partitioning of residuals plane ..........................................................................................................................17

7 Syntax and semantics ...................................................................................................................................................................................18

7.1 Method of specifying syntax in tabular form .............................................................................................................18

7.2 Specification of syntax functions and descriptors .................................................................................................19

7.3 Syntax in tabular form ...................................................................................................................................................................20

7.3.1 Syntax order ......................................................................................................................................................................20

7.3.2 NAL unit and NAL unit header syntax ........................................................................................................20

7.3.3 Process block syntax..................................................................................................................................................21

7.3.4 Process payload – sequence configuration ............................................................................................22

7.3.5 Process payload – global configuration .....................................................................................................22

7.3.6 Process payload – picture configuration ..................................................................................................24

7.3.7 Process payload – encoded data ......................................................................................................................25

7.3.8 Process payload – encoded tiled data .........................................................................................................26

7.3.9 Process payload – surface .....................................................................................................................................28

7.3.10 Process payload – additional info ...................................................................................................................29

7.3.11 Process payload – filler ........................................................................................................................................... .29

7.3.12 Byte alignment syntax ..............................................................................................................................................29

7.4 Semantics ..................................................................................................................................................................................................30

7.4.1 General...................................................................................................................................................................................30

7.4.2 NAL unit semantics .....................................................................................................................................................30

7.4.3 Data block unit configuration semantics .................................................................................................32

8 Decoding process ..............................................................................................................................................................................................41

8.1 General decoding process ...........................................................................................................................................................41

8.2 Payload data block unit process ............................................................................................................................................42

8.3 Picture enhancement decoding process ........................................................................................................................42

8.3.1 General enhancement decoding process .................................................................................................42

8.3.2 Decoding process for picture enhancement encoded data (payload_

encoded_data) .................................................................................................................................................................42

© ISO/IEC 2021 – All rights reserved iii
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ISO/IEC FDIS 23094-2:2021(E)
8.3.3 Decoding process for picture enhancement encoded tiled data (payload_

encoded_tiled_data) ...................................................................................................................................................45

8.3.4 Decoding process for enhancement sub-layer 1 (L-1) encoded data ..............................50

8.3.5 Decoding process for enhancement sub-layer 2 (L-2) encoded data ..............................52

8.4 Decoding process for the temporal prediction .........................................................................................................54

8.4.1 General decoding process for temporal prediction ........................................................................54

8.4.2 Tiled temporal refresh .............................................................................................................................................54

8.5 Decoding process for the dequantisation .....................................................................................................................54

8.5.1 Decoding process for the dequantisation overview .......................................................................54

8.5.2 Scaling process for transform coefficients .............................................................................................54

8.5.3 Derivation of dequantisation offset and stepwidth modifier .................................................55

8.5.4 Derivation of quantisation matrix..................................................................................................................56

8.6 Decoding process for the transform ..................................................................................................................................59

8.6.1 General upscaling process description ......................................................................................................59

8.6.2 Transform inputs and outputs, transform types, and residual samples

derivation ............................................................................................................................................................................64

8.6.3 2x2 directional decomposition transform ..............................................................................................64

8.6.4 4x4 directional decomposition transform ..............................................................................................65

8.7 Decoding process for the upscaling ...................................................................................................................................66

8.7.1 Nearest sample upsampler kernel description ..................................................................................66

8.7.2 Bilinear upsampler kernel description .....................................................................................................67

8.7.3 Cubic upsampler kernel description............................................................................................................70

8.7.4 Modified Cubic upsampler kernel description .................. ..................................................................73

8.7.5 Predicted residual process description .....................................................................................................74

8.7.6 Adaptive Cubic upsampler kernel description ....................................................................................75

8.8 Decoding process for the residual reconstruction ................................................................................................75

8.8.1 Reconstructed residual of each block derivation ..............................................................................75

8.8.2 Residual reconstruction for L-1 block ........................................................................................................76

8.8.3 Residual reconstruction for L-2 block ........................................................................................................76

8.9 Decoding process for the L-1 filter .....................................................................................................................................77

8.9.1 L-1 residual filter overview .................................................................................................................................77

8.9.2 Decoding process for filtering L-1 block ..................................................................................................77

8.10 Decoding process for base decoder data extraction ............................................................................................79

8.11 Decoding process for dither filter ........................................................................................................................................79

9 Parsing process ...................................................................................................................................................................................................79

9.1 Parsing process inputs and outputs, process overview ....................................................................................79

9.1.1 Parsing process for entropy encoded transform coefficients ................................................79

9.1.2 Parsing process for entropy encoded temporal signal coefficient group ....................82

9.2 Prefix Coding decoder ....................................................................................................................................................................83

9.2.1 Prefix Coding decoder description ................................................................................................................83

9.2.2 Prefix Coding decoder table generation ...................................................................................................84

9.2.3 Prefix Coding decoder for tile data sizes ..................................................................................................88

9.3 RLE decoder ...........................................................................................................................................................................................89

9.3.1 RLE process inputs and outputs ......................................................................................................................89

9.3.2 RLE decoder for coefficient groups ..............................................................................................................89

9.3.3 RLE decoder description .................. ......................................................................................................................90

9.3.4 RLE decoder for temporal signal coefficient group ........................................................................91

9.3.5 RLE decoder for tile entropy_enabled_flag fields .............................................................................93

9.4 Parsing process for 0-th order Exp-Golomb codes ...............................................................................................94

Annex A (normative) Profiles and levels .......................................................................................................................................................96

Annex B (normative) Byte stream format ....................................................................................................................................................98

Annex C (normative) Hypothetical reference decoder ...............................................................................................................101

Annex D (normative) Supplemental enhancement information .....................................................................................108

Annex E (normative) Video usability information ..........................................................................................................................115

Bibliography .........................................................................................................................................................................................................................119

iv © ISO/IEC 2021 – All rights reserved
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ISO/IEC FDIS 23094-2:2021(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that are

members of ISO or IEC participate in the development of International Standards through technical

committees established by the respective organization to deal with particular fields of technical

activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international

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work.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for

the 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 or www .iec .ch/ members

_experts/ refdocs).

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

Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents) or the IEC

list of patent declarations received (see patents.iec.ch).

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constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/

iso/ foreword .html. In the IEC, see www .iec .ch/ understanding -standards.

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.

A list of all parts in the ISO/IEC 23094 series can be found on the ISO and IEC websites.

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 and www .iec .ch/ national

-committees.
© ISO/IEC 2021 – All rights reserved v
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FINAL DRAFT INTERNATIONAL STANDARD ISO/IEC FDIS 23094-2:2021(E)
Information technology – General video coding —
Part 2:
Low complexity enhancement video coding
1 Scope
This document specifies low complexity enhancement video coding.
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.

ISO/IEC 11578:1996, Information technology — Open systems interconnection — Remote procedure call

(RPC)

ITU-T H.273 | ISO/IEC 23091-2:2019, Information technology — Coding-independent code points — Part 2:

Video

ITU-T Recommendation T.35:2000, Procedure for the allocation of ITU-T defined codes for non-standard

facilities
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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 https:// www .electropedia .org/
3.1
access unit

set of NAL units (3.35) that are associated with a particular output time, are consecutive in decoding

order (3.20), and contain exactly one coded picture (3.9)
3.2
bitstream

sequence of bits, in the form of a NAL unit stream (3.36) or a byte stream (3.6), that forms the

representation of coded pictures (3.9), and associated data forming one or more coded video sequences

(CVSs)
3.3
block

MxN (M-column by N-row) array of samples, or an MxN array of transform coefficients (3.57)

3.4
byte

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
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ISO/IEC FDIS 23094-2:2021(E)
3.5
byte-aligned

position in a bitstream (3.2) in which the position is an integer multiple of 8 bits from the position of the

first bit in the bitstream

Note 1 to entry: A bit, byte (3.4) or syntax element (3.53) is said to be byte-aligned when the position at which it

appears in a bitstream (3.2) is byte-aligned.
3.6
byte stream

encapsulation of a NAL unit stream (3.36) containing start code prefixes (3.51) and NAL units (3.35)

3.7
chroma

sample array or single sample is representing one of the two colour difference signals related to the

primary colours, represented by the symbols Cb and Cr

Note 1 to entry: 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.

3.8
chunk

entropy coded portion of data containing the quantised transform coefficient (3.57) belonging to a

coefficient group
3.9
coded picture

coded representation (3.10) of a picture (3.40) containing all TUs (3.58) of the picture

3.10
coded representation
data element as represented in its coded form
3.11
coded video sequence
CVS
coded sequence of access units (3.1)
3.12
coding block
MxN block (3.3) of samples for some values of M and N
3.13
coding unit

32 x 32 block (3.3) of samples resulting from the parsing of the entropy encoded transform coefficients

(3.57) in the decoding process (3.22)
3.14
coefficient group

syntactical structure containing coded data related to a specific set of transform coefficients (3.57)

3.15
component

array or single sample from one of the three arrays (luma (3.34) and two chroma (3.7)) that compose

a picture (3.40) 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
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ISO/IEC FDIS 23094-2:2021(E)
3.16
data block
syntax structure (3.54) containing bytes (3.4) corresponding to a type of data
3.17
decoded base picture

decoded picture (3.18) derived by decoding a coded picture (3.9) with a base decoder (3.20)

3.18
decoded picture

picture (3.40) derived by decoding a coded picture (3.9), and which is either a decoded frame (3.29) or a

decoded field (3.28)
3.19
decoded picture buffer
DPB
buffer holding decoded pictures (3.18) for reference or output reordering
3.20
decoder
embodiment of a decoding process (3.22)
3.21
decoding order

order in which syntax elements (3.53) are processed by the decoding process (3.22)

3.22
decoding process

process specified that reads a bitstream (3.2) and derives decoded pictures (3.18) from it

3.23
emulation prevention byte

byte (3.4) equal to 0x03 that may be present within a NAL unit (3.35), the presence of which ensures that

no sequence of consecutive byte-aligned (3.5) bytes in the NAL unit contains a start code prefix (3.51)

3.24
encoder
embodiment of an encoding process (3.25)
3.25
encoding process
process that produces a bitstream (3.2) conforming to this document
3.26
enhancement layer
layer (3.32) within the bitstream (3.2) pertaining to the residual planes (3.47)
3.27
enhancement sub-layer
layer (3.32) of the enhancement layer (3.26)
3.28
field
assembly of alternate rows of a frame (3.29)
3.29
frame

array of luma (3.34) samples in monochrome format or array of luma samples and two corresponding

arrays of chroma (3.7) samples in 4:2:0, 4:2:2, and 4:4:4 colour format, and which consists of two fields

(3.28): a top field and a bottom field
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ISO/IEC FDIS 23094-2:2021(E)
3.30
instantaneous decoding refresh picture
IDR picture

picture (3.40) for which a NAL unit (3.35) contains a global configuration data block and does not

refer to any other picture for operation of the decoding process (3.22) of this picture and for which no

subsequent pictures in decoding order (3.21) refer to any picture that precedes it in decoding order

Note 1 to entry: An IDR picture shall occur at least when an IDR picture for the base decoder (3.20) occurs. The

IDR picture for a base decoder is not specified in this document.
3.31
inverse transform

part of the decoding process (3.22) by which a set of transform coefficients (3.57) is converted into

residuals (3.46)
3.32
layer

one of a set of syntactical structures in a non-branching hierarchical relationship

3.33
level

defined set of constraints on the values that may be taken by the syntax elements (3.53) and variables of

this document

Note 1 to entry: The same set of levels is defined for all profiles (3.41), with most aspects of the definition of each

level being in common across different profiles. Individual implementations may, within specified constraints,

support a different level for each supported profile.
3.34
luma

sample array or single sample representing the monochrome signal related to the primary colours,

represented by the symbol or subscript Y or L

Note 1 to entry: 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.

3.35
network abstraction layer unit
NAL unit

syntax structure (3.54) containing an indication of the type of data to follow and bytes (3.4) containing

that data in the form of an RBSP (3.42) interspersed as necessary with emulation prevention bytes (3.23)

3.36
network abstraction layer unit stream
...

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