ISO/IEC 23094-3:2022
(Main)Information technology -- General video coding
Information technology -- General video coding
Technologies de l'information -- Codage vidéo général
General Information
Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 23094-3
First edition
2022-09
Information technology — General
video coding —
Part 3:
Conformance and reference software
for low complexity enhancement
video coding
Technologies de l'information — Codage vidéo général —
Partie 3: Conformité et logiciel de référence pour le codage vidéo
d'amélioration de faible complexité
Reference number
ISO/IEC 23094-3:2022(E)
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ISO/IEC 23094-3:2022(E)
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ISO/IEC 23094-3:2022(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Conventions . 2
6 Conformance testing for ISO/IEC 23094-2 . 3
6.1 General . 3
6.2 Bitstream conformance . 3
6.3 Decoder conformance . 3
6.4 Procedure to test bitstreams . 3
6.5 Procedure to test decoder conformance . 4
6.5.1 Conformance bitstreams . 4
6.5.2 Contents of the bitstream file . 4
6.5.3 Operation modes for decoder conformance testing . 4
6.5.4 Requirements on output of the decoding process and timing . 4
6.5.5 Recommendations. 5
6.5.6 Static tests for output order conformance . 5
6.5.7 Dynamic tests for output timing conformance . 5
6.5.8 Decoder conformance test of a particular profile and level . 6
6.6 Specification of the test bitstreams . 6
6.6.1 General . 6
6.6.2 Test bitstreams . 7
6.7 Normative test suites for ISO/IEC 23094-2. 18
7 Reference software description .21
7.1 General . 21
7.2 LTM repository .22
7.3 Encoder usage . 22
7.4 Decoder usage .23
Annex A (informative) Information on accuracy tolerance of decoding implementations.25
Annex B (informative) Demultiplexing of test bitstreams .26
Bibliography .27
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ISO/IEC 23094-3:2022(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 https://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.
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INTERNATIONAL STANDARD ISO/IEC 23094-3:2022(E)
Information technology — General video coding —
Part 3:
Conformance and reference software for low complexity
enhancement video coding
1 Scope
This document specifies a set of tests and procedures designed to verify whether bitstreams and
decoders meet normative requirements specified in ISO/IEC 23094-2.
An encoder can claim conformance to ISO/IEC 23094-2 if the bitstreams that it generates are conforming
bitstreams. Characteristics of coded bitstreams and decoders are defined in ISO/IEC 23094-2. Decoder
characteristics define the properties and capabilities of the applied decoding process. The capabilities
of a decoder specify which bitstreams the decoder can decode and reconstruct. A bitstream can be
decoded by a decoder if the characteristics of the bitstream are within the specified decoder capabilities.
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 23094-2:2021, Information technology – General video coding — Part 2: Low complexity
enhancement video coding
ISO/IEC 14882, Programming languages — C++
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 23094-2 and the following
apply.
ISO and IEC maintain terminology 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
bitstream
sequence of bits in the form of a NAL unit stream or a raw bitstream, that forms the representation of
coded pictures and associated data forming one or more coded video sequences
3.2
decoder
embodiment of a process that operates on a bitstream (3.1) and may conform to the decoding process
requirements specified for conformance
Note 1 to entry: The decoder does not include the display process, which is outside the scope of this document.
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ISO/IEC 23094-3:2022(E)
3.3
encoder
embodiment of a process that produces a bitstream (3.1)
Note 1 to entry: The process is not specified in this document (except in regard to identification of the reference
software encoder).
3.4
reference software decoder
software which may decode a bitstream (3.1) encoded according to the syntax structure and which is
accompanying this document
3.5
reference software encoder
encoding software which is accompanying this document
3.6
test base bitstream
bitstream (3.1) that is conformant to Rec. ITU-T H.264 | ISO/IEC 14496-10 or Rec. ITU-T H.265 |
ISO/IEC 23008-2
3.7
test bitstream
bitstream (3.1) that is the combination of a test base bitstream (3.6) and a test enhancement bitstream
(3.8)
3.8
test enhancement bitstream
bitstream (3.1) that is conformant to ISO/IEC 23094-2
4 Abbreviated terms
For the purposes of this document, the abbreviated terms given in ISO/IEC 23094-2 and the following
apply.
API Application programming interface
AVC Advanced video coding
EVC Essential video coding
HEVC High efficiency video coding
LTM LCEVC test model
VVC Versatile video coding
5 Conventions
For the purposes of this document, relevant conventions are specified in of ISO/IEC 23094-2:2021,
Clause 5.
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ISO/IEC 23094-3:2022(E)
6 Conformance testing for ISO/IEC 23094-2
6.1 General
The following subclauses specify normative tests for verifying conformance of video bitstreams as well
as decoders. Those normative tests make use of test data (bitstream test suites) provided as an electronic
attachment to this document and the reference software decoder specified in ISO/IEC 23094-2.
For the purpose of testing according to 6.5, test bitstreams are provided in the bitstream test suite. In
the following subclauses, the normative tests use the test bitstreams for verifying the conformance of
the decoding process of the test enhancement bitstreams.
A test base bitstream is conformant in accordance with the respective International Standard it
implements. The conformance testing of the test base bitstream is not in the scope of this document.
This document includes an electronic attachment containing the conformance bitstreams identified
within the text and the reference software. The electronic attachment is available at the following
address: https:// standards .iso .org/ iso -iec/ 23094/ -3/ ed -1/ en/ .
6.2 Bitstream conformance
Bitstream conformance for ISO/IEC 23094-2 is specified by ISO/IEC 23094-2:2021, C.4.
6.3 Decoder conformance
Decoder conformance for ISO/IEC 23094-2 is specified by ISO/IEC 23094-2:2021, C.5.
6.4 Procedure to test bitstreams
A bitstream that claims conformance with ISO/IEC 23094-2 shall pass the following normative test.
The bitstream shall be decoded by processing it with the reference software decoder. When processed by
the reference software decoder, the bitstream shall not cause any error or non-conformance messages
to be reported by the reference software decoder. This test should not be applied to bitstreams that
are known to contain errors introduced by transmission, as such errors are highly likely to result in
bitstreams that lack conformance to ISO/IEC 23094-2.
Successfully passing the reference software decoder test provides only a strong presumption that the
bitstream under test is conforming to the video layer, i.e., that it does indeed meet all the requirements
for the video layer (except Annexes C, D, and E) specified in ISO/IEC 23094-2 that are tested by the
reference software decoder.
Additional tests may be necessary to more thoroughly check that the bitstream properly meets all
the requirements specified in ISO/IEC 23094-2 including the hypothetical reference decoder (HRD)
conformance (based on Annexes C, D, and E). These complementary tests may be performed using other
video bitstream verifiers that perform more complete tests than those implemented by the reference
software decoder.
ISO/IEC 23094-2 contains several informative recommendations that are not an integral part of that
International Standard. When testing a bitstream for conformance, it may also be useful to test whether
or not the bitstream follows those recommendations.
To check correctness of a bitstream, it is necessary to parse the entire bitstream and to extract all the
syntax elements and other values derived from those syntactic elements and used by the decoding
process specified in ISO/IEC 23094-2.
A verifier may not necessarily perform all stages of the decoding process specified in ISO/IEC 23094-2
in order to verify bitstream correctness. Many tests can be performed on syntax elements in a state
prior to their use in some processing stages.
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ISO/IEC 23094-3:2022(E)
Annex A of this document provides information on the accuracy tolerance of decoding implementations
if a different precision than the fixed-point precision specified in ISO/IEC 23094-2 is used.
6.5 Procedure to test decoder conformance
6.5.1 Conformance bitstreams
A bitstream has values of profile_idc and level_idc corresponding to a set of specified constraints on
a bitstream for which a decoder conforming to a specified profile and level is required in Annex A of
ISO/IEC 23094-2:2021 to properly perform the decoding process.
6.5.2 Contents of the bitstream file
The conformance bitstreams are included in this document as an electronic attachment. The following
information might be included in a single zipped file for each such bitstream.
— *.bit – bitstream
— *.txt – description
— *.yuv.md5 – MD5 check sum of the complete decoded yuv file
— *.md5 – MD5 check sum of the bitstream file
— *.opl – output picture log
— *.cfg – config file used to generate bitstream with LTM reference software encoder
— *_userdata.bin – Byte file with the content of the user data present within the bitstream
In case a single zipped file contains multiple bitstreams, each bitstream shall be tested separately. The
above listed files are available for each such bitstream within the zipped file.
6.5.3 Operation modes for decoder conformance testing
For decoder conformance testing, there are two operation modes:
1) Operation mode A: The reference software decoder may be used to separate the test enhancement
bitstream from the test bitstream and to generate the decoded base pictures, as specified in
Annex B. A decoder shall use as inputs the decoded base pictures and the test enhancement
bitstream. In this operation mode, the decoder shall be able to decode the test enhancement
bitstream in accordance with ISO/IEC 23094-2:2021, C.1.
2) Operation mode B: A decoder shall use as an input the test bitstream as provided. In this
operation mode, the decoder shall be able to decode the test bitstream in accordance with
ISO/IEC 23094-2:2021, C.1.
A decoder under test may choose either of the two operation modes to verify decoder conformance.
6.5.4 Requirements on output of the decoding process and timing
Two classes of decoder conformance are specified:
— output order conformance; and
— output timing conformance.
The output of the decoding process is specified in ISO/IEC 23094-2:2021, Clause 8 and Annex C.
For output order conformance, it is a requirement that all of the decoded pictures specified for output
in ISO/IEC 23094-2:2021, Annex C shall be output by a conforming decoder in the specified order and
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ISO/IEC 23094-3:2022(E)
that the values of the decoded samples in all of the pictures that are output shall be the values specified
in ISO/IEC 23094-2:2021, Clause 8.
For output timing conformance, it is a requirement that a conforming decoder shall also output the
decoded samples at the rates and times specified in ISO/IEC 23094-2:2021, Annex C.
The display process, which ordinarily follows the output of the decoding process, is outside the scope of
this document.
6.5.5 Recommendations
This clause does not form an integral part of this document.
In addition to the requirements, it is desirable that conforming decoders implement various informative
recommendations specified in ISO/IEC 23094-2 that are not an integral part of that International
Standard. This clause discusses some of these recommendations.
It is recommended that a conforming decoder be able to resume the decoding process as soon as possible
after the loss or corruption of part of a bitstream. In most cases it is possible to resume decoding at the
next IDR NALu. It is recommended that a conforming decoder be able to perform concealment for the
video packets for which all the coded data has not been received.
6.5.6 Static tests for output order conformance
Static tests of a video decoder require testing of the decoded samples. This clause will explain how this
test can be accomplished when the decoded samples at the output of the decoding process are available.
It may not be possible to perform this type of test with a production decoder (due to the lack of an
appropriate accessible interface in the design at which to perform the test). In that case this test should
be performed by the manufacturer during the design and development phase. Static tests are used for
testing the decoding process. The test will check that the values of the samples decoded by the decoder
under test shall be identical to the values of the samples decoded by the reference decoder. When a hash
of the values of the samples of the decoded pictures is attached to the bitstream file, a corresponding
hash operation performed on the values of the samples of the decoded pictures produced by the decoder
under test shall produce the same results.
6.5.7 Dynamic tests for output timing conformance
Dynamic tests are applied to check that all the decoded samples are output and that the timing of
the output of the decoder's decoded samples conforms to the specification of ISO/IEC 23094-2:2021,
Clause 8 and Annex C and to verify that the HRD models (as specified by the CPB and DPB specification
in ISO/IEC 23094-2:2021, Annex C) are not violated when the bits of the bitstream are delivered at the
proper rate.
The dynamic test is often easier to perform on a complete decoding system, which may include a
systems decoder, a video decoder and a display process. It may be possible to record the output of
the display process and to check that display order and timing of decoded pictures are correct at the
output of the display process. However, since the display process is not within the normative scope of
ISO/IEC 23094-2, there may be cases where the output of the display process differs in timing or value
even though the video decoder is conforming. In this case, the output of the video decoder itself (before
the display process) would need to be captured in order to perform the dynamic tests on the video
decoder. In particular the output order and timing of the decoded pictures shall be correct.
If buffering period and picture timing SEI messages are included in the base test bitstream, HRD
conformance shall be verified using the values of initial_cpb_removal_delay, initial_cpb_removal_delay_
offset, cpb_removal_delay and dpb_removal_delay that are included in the base test bitstream.
If buffering period and picture timing SEI messages are not included in the base test bitstream, the
following inferences shall be made to generate the missing parameters:
— fixed_pic_rate_flag shall be inferred to be equal to 1.
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ISO/IEC 23094-3:2022(E)
— low_delay_hrd_flag shall be inferred to be equal to 0.
— cbr_flag shall be inferred to be equal to 0.
— The frame rate of the bitstream shall be inferred to be equal to the frame rate value specified in
Table 1, where the bitstream is listed. If this is missing, then a frame rate of either 25 or 30 000 ÷
1 001 can be inferred.
— time_scale shall be set equal to 90 000 and the value of num_units_in_tick shall be computed based
on frame rate.
— The bit rate of the base test bitstream shall be inferred to be equal to the maximum value for the
level specified in the specification that the base test bitstream implements.
— CPB and DPB sizes shall be inferred to be equal to the maximum value for the level as stated in the
specification of the base.
With the above inferences, the HRD shall be operated as follows.
— The CPB is filled starting at time t = 0, until it is full, before removal of the first access unit. This
means that the initial_cpb_removal_delay shall be inferred to be equal to the total CPB buffer size
divided by the bit rate divided by 90 000 (rounded downwards) and initial_cpb_removal_delay_
offset shall be inferred to be equal to zero.
— The first access unit is removed at time t = initial_cpb_removal_delay ÷ 90 000 and subsequent
access units are removed at intervals based on the frame distance, i.e., 2 * (90 000 ÷ num_units_in_
tick) or the field distance, i.e., (90 000 / num_units_in_tick), depending on whether the access unit
is coded as a frame picture or field picture.
— Using these inferences, the CPB will not overflow or underflow and the DPB will not overflow.
6.5.8 Decoder conformance test of a particular profile and level
In order for a decoder of a particular profile and level to claim output order conformance to
ISO/IEC 23094-2 as specified by this document, the decoder shall successfully pass the static test
specified in 6.5.6 with all the bitstreams of the normative test suite specified for testing decoders of
this particular profile and level combination.
In order for a decoder of a particular profile and level to claim output timing conformance to
ISO/IEC 23094-2 as specified by this document, the decoder shall successfully pass both the static test
specified in 6.5.6 and the dynamic test specified in 6.5.7 with all the bitstreams of the normative test
suite specified for testing decoders of this particular profile and level. Table 1 specifies the normative
test suites for each profile and level combination. The test suite for a particular profile and level
combination is the list of bitstreams that are marked with an 'X' in the column corresponding to that
profile and level combination.
'X' indicates that the bitstream is designed to test both the dynamic and static conformance of the
decoder.
The bitstream column specifies the bitstream used for each test.
A decoder that conforms to the profiles at a specific level shall be capable of decoding the specified
bitstreams in Table 1.
6.6 Specification of the test bitstreams
6.6.1 General
Some characteristics of each bitstream listed in Table 1 are specified in this clause.
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6.6.2 Test bitstreams
6.6.2.1 Test bitstream MP_SET-1
Specification: Streams with sets of coding tools in Main profile.
Functional stage: Test the decoding process of Main profile.
Purpose: Check that the decoder can properly decode bitstreams in which the full set of coding tools in
Main profile is enabled.
6.6.2.2 Test bitstream TT-1
Specification: Streams with 2x2 directional decomposition transform used in Main profile.
Functional stage: Test the decoding process of the 2x2 directional decomposition transform in Main
profile.
Purpose: Check that the decoder can properly decode bitstreams in which the 2x2 directional
decomposition transform is used in Main profile.
6.6.2.3 Test bitstream TT-2
Specification: Streams with 4x4 directional decomposition transform changed to 2x2 directional
decomposition transform changed to 4x4 directional decomposition transform used in Main profile.
Functional stage: Test the decoding process with changes of the kernel size of the directional
decomposition transform within the bitstream in Main profile.
Purpose: Check that the decoder can properly decode bitstreams in which the kernel size of the
directional decomposition transform is changed within the bitstream in Main profile.
6.6.2.4 Test bitstream UPS-1
Specification: Streams with the nearest sample upsampler kernel used in Main profile.
Functional stage: Test the decoding process of the nearest sample upsampler kernel in Main profile.
Purpose: Check that the decoder can properly decode bitstreams in which the nearest sample upsampler
kernel is used in Main profile.
6.6.2.5 Test bitstream UPS-2
Specification: Streams with the bilinear upsampler kernel used in Main profile.
Functional stage: Test the decoding process of the bilinear upsampler kernel in Main profile.
Purpose: Check that the decoder can properly decode bitstreams in which the bilinear upsampler kernel
is used in Main profile.
6.6.2.6 Test bitstream UPS-3
Specification: Streams with the cubic upsampler kernel used in Main profile.
Functional stage: Test the decoding process of the cubic upsampler kernel in Main profile.
Purpose: Check that the decoder can properly decode bitstreams in which the cubic upsampler kernel is
used in Main profile.
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6.6.2.7 Test bitstream UPS-4
Specification: Streams with the modified cubic upsampler kernel used in Main profile.
Functional stage: Test the decoding process of the modified cubic upsampler kernel in Main profile.
Purpose: Check that the decoder can properly decode bitstreams in which the modified cubic upsampler
kernel is used in Main profile.
6.6.2.8 Test bitstream UPS-5
Specificat
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