ISO/IEC 13818-2:1996
(Main)Information technology — Generic coding of moving pictures and associated audio information: Video
Information technology — Generic coding of moving pictures and associated audio information: Video
Technologies de l'information — Codage générique des images animées et du son associé: Données vidéo
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INTERNATIONAL lSO/lEC
STANDARD 13818-2
First edition
1996-05-15
Information technology - Generic coding
of moving pictures and associated audio
information: Video
Technologies de I’informa tion - Codage des images animees et du son
associb: Vid6o
Reference number
lSO/IEC 13818-2:1996(E)
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ISO/IEC 13818-2: 1996(E)
CONTENTS
Page
1
Scope .
1
.....................................................................................................................................
Normative references
2
......................................................................................................................................................
Definitions
8
Abbreviations and symbols .
8
4.1 Arithmetic operators .
8
4.2 Logical operators .
9
............................................................................................................................
4.3 Relational operators
9
4.4 Bitwise operators .
9
.........................................................................................................................................
4.5 Assignment
9
..........................................................................................................................................
4.6 Mnemonics
9
.............................................................................................................................................
4.7 Constants
9
Conventions .
5
9
...............................................................................................
5.1 Method of describing bitstream syntax
10
........................................................................................................................
5.2 Definition of functions
11
...................................................................................................
5.3 Reserved, forbidden and marker - bit
11
............................................................................................................................
5.4 Arithmetic precision
11
...........................................................................................................
6 Video bitstream syntax and semantics
11
Structure of coded video data .
6.1
23
Video bitstream syntax .
6.2
39
Video bitstream semantics .
6.3
62
...........................................................................................................................
7 The video decoding process
63
..................................................................................................................
7.1 Higher syntactic structures
63
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7.2 Variable length decoding
66
Inverse scan .
7.3
68
Inverse quantisation .
7.4
72
7.5 Inverse DCT .
73
7.6 Motion compensation .
87
7.7 Spatial scalability .
100
7.8 SNR scalability .
105
7.9 Temporal scalability ~.~,.”.“~~.“.“.“.” .
108
7.10 Data partitioning .
109
7.11 Hybrid scalability .
110
...........................................................................................................
7.12 Output of the decoding process
114
8 Profiles and levels .
115
8.1 ISO/IEC 11172-2 compatibility .
115
................................................................................................
8.2 Relationship between defined profiles
117
...................................................................................................
8.3 Relationship between defined levels
118
....................................................................................................................................
8.4 Scalable layers
121
8.5 .
Parameter values for defined profiles, levels and layers
0 ISO/IEC 1996
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ISO/IEC Copyright Office l Case postale 56 l CH- 12 11 Geneve 20 l Switzerland
Printed in Switzerland
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0 ISOIIEC ISO/IEC 13818-2: 1996(E)
125
Annex A - Discrete cosine transform .
126
..................................................................................................................
Annex B - Variable length code tables
126
Macroblock addressing .
B.l
127
.................................................................................................................................
B.2 Macroblock type
132
.............................................................................................................................
B.3 Macroblock pattern
133
B.4 Motion vectors .
134
DCT coefficients .
B.5
143
Video buffering verifier .
Annex C -
148
Annex D - Features supported by the algorithm .
148
D.1 Overview .
148
D.2 Video formats .
149
D.3 Picture quality .
149
D.4 Data rate control .
150
D.5 Low delay mode .
150
........................................................................................................
D.6 Random access/channel hopping
150
D.7 Scalability .
157
Compatibility .
D.8
157
...........................................................
D.9 Differences between this Specification and ISO/IEC 11172-2
160
D.10 Complexity .
160
D.11 Editing encoded bitstreams .
160
D.12 Trick modes .
161
D.13 Error resilience .
168
D.14 Concatenated sequences .
................................................................................................................. 169
Annex E - Profile and level restrictions
................................................................................................ 169
E.l Syntax element restrictions in profiles
180
...........................................................................................................
E.2 Permissible layer combinations
201
..........................................................................................................................................
Annex F - Bibliography
iii
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ISO/IEC 13818=2:1996(E)
0 ISO/IEC
Foreword
IS0 (the International Organization for Standardization) and IEC (the
International Electrotechnical Commission) form the specialized system for
worldwide standardization. National bodies that are members of IS0 or IEC par-
ticipate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields
of technical activity. IS0 and IEC technical committees collaborate in fields of
mutual interest. Other international organizations, governmental and non-
governmental, in liaison with IS0 and IEC, also take part in the work.
In the field of information technology, IS0 and IEC have established a joint
technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the
joint technical committee are circulated to national bodies for voting. Publication
as an International Standard requires approval by at least 75 % of the national
bodies casting a vote.
International Standard ISO/IEC 138 18-2 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 identical text is published as ITU-T
Recommendation H.262.
ISO/IEC 13818 consists of the following parts, under the general title Information
technology - Generic coding of moving pictures and associated audio
information:
- Part 1: Systems
- Part 2: Video
- Part 3: Audio
- Part 4: Compliance testing
- Part 6: Extensions for DSM-CC
- Part 9: Extension for real time inte$ace for systems decoders
Annexes A to C form an integral part of this part of ISO/IEC 13818. Annexes D to
F are for information only.
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@ ISOIIEC
ISO/IEC 13818-2: 1996(E)
Introduction
Intro. 1 Purpose
This Part of this Specification was developed in response to the growing need for a generic coding method of moving
pictures and of associated sound for various applications such as digital storage media, television broadcasting and
communication. The use of this Specification means that motion video can be manipulated as a form of computer data
and can be stored on various storage media, transmitted and received over existing and future networks and distributed
on existing and future broadcasting channels.
Intro. 2 Application
The applications of this Specification cover, but are not limited to, such areas as listed below:
BSS Broadcasting Satellite Service (to the home)
CATV Cable TV Distribution on optical networks, copper, etc.
CDAD Cable Digital Audio Distribution
DSB Digital Sound Broadcasting (terrestrial and satellite broadcasting)
DTTB Digital Terrestrial Television Broadcasting
EC Electronic Cinema
EN6 Electronic News Gathering (including SNG, Satellite News Gathering)
FSS Fixed Satellite Service (e.g. to head ends)
HTT Home Television Theatre
IPC Interpersonal Communications (videoconferencing, videophone, etc.)
ISM Interactive Storage Media (optical disks, etc.)
MMM Multimedia Mailing
NCA News and Current Affairs
NDB Networked Database Services (via ATM, etc.)
RVS Remote Video Surveillance
SSM Serial Storage Media (digital VTR, etc.)
Intro. 3 Profiles and levels
This Specification is intended to be generic in the sense that it serves a wide range of applications, bitrates, resolutions,
qualities and services. Applications should cover, among other things, digital storage media, television broadcasting and
communications. In the course of creating this Specification, various requirements from typical applications have been
considered, necessary algorithmic elements have been developed, and they have been integrated into a single syntax.
Hence, this Specification will facilitate the bitstream interchange among different applications.
Considering the practicality of implementing the full syntax of this Specification, however, a limited number of subsets
of the syntax are also stipulated by means of “profile” and “level”. These and other related terms are formally defined in
clause 3.
A “profile” is a defined subset of the entire bitstream syntax that is defined by this Specification. Within the bounds
imposed by the syntax of a given profile it is still possible to require a very large variation in the performance of
encoders and decoders depending upon the values taken by parameters in the bitstream. For instance, it is possible to
specify frame sizes as large as (approximately) 214 samples wide by 214 lines high. It is currently neither practical nor
economic to implement a decoder capable of dealing with all possible frame sizes.
In order to deal with this problem, “levels” are defined within each profile. A level is a defined set of constraints
imposed on parameters in the bitstream. These constraints may be simple limits on numbers. Alternatively they may take
the form of constraints on arithmetic combinations of the parameters (e.g. frame width multiplied by frame height
multiplied by frame rate).
Bitstreams complying with this Specification use a common syntax. In order to achieve a subset of the complete syntax,
flags and parameters are included in the bitstream that signal the presence or otherwise of syntactic elements that occur
later in the bitstream. In order to specify constraints on the syntax (and hence define a profile) it is thus only necessary to
constrain the values of these flags and parameters that specify the presence of later syntactic elements.
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0 ISO/IEC
ISO/IEC 13818-2: 1996(E)
Intro. 4 The scalable and the non-scalable syntax
The full syntax can be divided into two major categories: One is the non-scalable syntax, which is structured as a super
set of the syntax defined in ISO/IEC 11172-2. The main feature of the non-scalable syntax is the extra compression tools
for interlaced video signals. The second is the scalable syntax, the key property of which is to enable the reconstruction
of useful video from pieces of a total bitstream. This is achieved by structuring the total bitstream in two or more layers,
starting from a standalone base layer and adding a number of enhancement layers. The base layer can use the non-
scalable syntax, or in some situations conform to the ISOLIEC 11172-2 syntax.
Intro. 4.1 Overview of the non-scalable syntax
The coded representation defined in the non-scalable syntax achieves a high compression ratio while preserving good
image quality. The algorithm is not lossless as the exact sample values are not preserved during coding. Obtaining good
image quality at the bitrates of interest demands very high compression, which is not achievable with intra picture
coding alone. The need for random access, however, is best satisfied with pure intra picture coding. The choice of the
techniques is based on the need to balance a high image quality and compression ratio with the requirement to make
random access to the coded bitstream.
A number of techniques are used to achieve high compression” The algorithm first uses block-based motion
compensation to reduce the temporal redundancy. Motion compensation is used both for causal prediction of the current
picture from a previous picture, and for non-causal, interpolative prediction from past and future pictures. Motion
vectors are defined for each 1 &sample by 16-line region of the picture. The prediction error, is further compressed using
the Discrete Cosine Transform (DCT) to remove spatial correlation before it is quantised in an irreversible process that
discards the less important information. Finally, the motion vectors are combined with the quantised DCT information,
and encoded using variable length codes.
Intro. 4.1.1 Temporal processing
Because of the conflicting requirements of random access and highly efficient compression, three main picture types are
defined. Intra Coded Pictures (I-Pictures) are coded without reference to other pictures. They provide access points to
the coded sequence where decoding can begin, but are coded with only moderate compression. Predictive Coded
Pictures (P-Pictures) are coded more efficiently using motion compensated prediction from a past intra or predictive
coded picture and are generally used as a reference for further prediction. Bidirectionally-predictive Coded Pictures
(B-Pictures) provide the highest degree of compression but require both past and future reference pictures for motion
compensation. Bidirectionally-predictive coded pictures are never used as references for prediction (except in the case
that the resulting picture is used as a reference in a spatially scalable enhancement layer). The organisation of the three
picture types in a sequence is very flexible. The choice is left to the encoder and will depend on the requirements of the
application. Figure Intro. 1 illustrates an example of the relationship among the three different picture types.
Bidirectional Interpolation
Figure Intro. 1 - Example of temporal picture structure
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o ISOIIEC ISO/IEC 13818=2:1996(E)
Intro. 4.1.2 Coding interlaced video
Each frame of interlaced video consists of two fields which are separated by one field-period. The Specification allows
either the frame to be encoded as picture or the two fields to be encoded as two pictures. Frame encoding or field
encoding can be adaptively selected on a frame-by-frame basis. Frame encoding is typically preferred when the video
scene contains significant detail with limited motion. Field encoding, in which the second field can be predicted from the
first, works better when there is fast movement.
Intro. 4.1.3 Motion representation - Macroblocks
As in ISO/IEC 11172-2, the choice of 16 by 16 macroblocks for the motion-compensation unit is a result of the trade-off
between the coding gain provided by using motion information and the overhead needed to represent it. Each
macroblock can be temporally predicted in one of a number of different ways. For example, in frame encoding, the
prediction from the previous reference frame can itself be either frame-based or field-based. Depending on the type of
the macroblock, motion vector information and other side information is encoded with the compressed prediction error
in each macroblock. The motion vectors are encoded differentially with respect to the last encoded motion vectors using
variable length codes. The maximum length of the motion vectors that may be represented can be programmed, on a
picture-by-picture basis, so that the most demanding applications can be met without compromising the performance of
the system in more normal situations.
It is the respo nsibili ty of the en coder to calculate appropriate motion vectors. This Specification does not specify how
this should be done.
Intro. 4.1.4 Spatial redundancy reduction
Both source pictures and prediction errors have high spatial redundancy. This Specification uses a block-based DCT
method with visually weighted quantisation and run-length coding. After motion compensated prediction or
interpolation, the resulting prediction error is split into 8 by 8 blocks. These are transformed into the DCT domain where
they are weighted before being quantised. After quantisation many of the DCT coefficients are zero in value and so
two-dimensional run-length and variable length coding is used to encode the remaining DCT coefficients efficiently.
Intro. 4.1.5 Chrominance formats
In addition to the 4:2:0 format supported in ISO/IEC 11172-2 this Specification supports 4:2:2 and 4:4:4 chrominance
formats.
Intro. 4.2 Scalable extensions
The scalability tools in this Specification are designed to support applications beyond that supported by single layer
video. Among the noteworthy applications areas addressed are video telecommunications, video on Asynchronous
Transfer Mode networks (ATM), interworking of video standards, video service hierarchies with multiple spatial,
temporal and quality resolutions, HDTV with embedded TV, systems allowing migration to higher temporal resolution
HDTV, etc. Although a simple solution to scalable video is the simulcast technique which is based on
transmission/storage of multiple independently coded reproductions of video, a more efficient alternative is scalable
video coding, in which the bandwidth allocated to a given reproduction of video can be partially re-utilised in coding of
the next reproduction of video. In scalable video coding, it is assumed that given a coded bitstream, decoders of various
complexities can decode and display appropriate reproductions of coded video. A scalable video encoder is likely to
have increased complexity when compared to a single layer encoder. However, this Recommendation I International
Standard provides several different forms of scalabilities that address non-overlapping applications with corresponding
complexities. The basic scalability tools offered are:
-
data partitioning;
-
SNR scalability;
-
spatial scalability; and
-
temporal
scalability.
Moreover, combinations of these basic scalability tools are also supported and are referred to as hybrid scalability. In the
case of basic scalability, two layers of video referred to as the lower layer and the enhancement layer are allowed,
whereas in hybrid scalability up to three layers are supported. Tables Intro. 1 to Intro. 3 provide a few example
applications of various scalabilities.
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ISO/IEC 13818-2: 1996(E)
0 ISO/IEC
Table Intro. 1 - Applications of SNR scalability
*
Lower layer Enhancement layer Application
Recommendation Same resolution and format as Two quality service for Standard TV (SDTV)
ITU-R BT.601 lower layer
High Definition Same resolution and format as Two quality service for HDTV
lower layer
Video production / distribution
4:2:0 high definition 4:2:2 chroma simulcast
Table Intro. 2 - Applications of spatial scalability
Base Enhancement Application
Progressive (30 Hz) Progressive (30 Hz)
Interlace (30 Hz) Interlace (30 Hz) 1 HDTWSDTV scalability
I I I
1 Progressive (30 Hz) I Interlace (30 Hz) ISO/IEC 11172-28compatibility with this Specification
I
I
Interlace (30 Hz) I Progressive (60 Hz) I Migration to high resolution progressive HDTV
I I
Table Intro. 3 - Applications of temporal scalability
Enhancement Higher Application
Base
I
I I I
Progressive (30 Hz) 1 ProgT(gressive (60 Hz) 1 Migration HDTV to high ~~ resolution progressive
r
Interlace (30 Hz) Interlace (30 Hz) Progressive (60 Hz) Migration to high resolution progressive
HDTV
r I
I
Intro. 4.2.1 Spatial scalable extension
Spatial scalability is a tool intended for use in video applications involving telecommunications, interworking of video
standards, video database browsing, interworking of HDTV and TV, etc., i.e. video systems with the primary common
feature that a minimum of two layers of spatial resolution are necessary. Spatial scalability involves generating two
spatial resolution video layers from a single video source such that the lower layer is coded by itself to provide the basic
spatial resolution and the enhancement layer employs the spatially interpolated lower layer and carries the full spatial
resolution of the input video source. The lower and the enhancement layers may either both use the coding tools in this
Specification, or the ISO/IEC 11172-2 Standard for the lower layer and this Specification for the enhancement layer.
The latter case achieves a further advantage by facilitating interworking between video coding standards. Moreover,
spatial scalability offers flexibility in choice of video formats to be employed in each layer. An additional advantage of
spatial scalability is its ability to provide resilience to transmission errors as the more important data of the lower layer
can be sent over channel with better error performance, while the less critical enhancement layer data can be sent over a
channel with poor error performance.
Intro. 4.2.2 SNR scalable extension
SNR scalability is a tool intended for use in video applications involving telecommunications, video services with
multiple qualities, standard TV and HDTV, i.e. video systems with the primary common feature that a minimum of two
layers of video quality are necessary. SNR scalability involves generating two video layers of same spatial resolution but
different video qualities from a single video source such that the lower layer is coded by itself to provide the basic video
quality and the enhancement layer is coded to enhance the lower layer. The enhancement layer when added back to the
. . .
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0 ISO/IEC
ISO/IEC 13818-2: 1996(E)
lower layer regenerates a higher quality reproduction of the input video. The lower and the enhancement layers may
either use this Specification or ISO/IEC 11172-2 Standard for the lower layer and this Specification for the enhancement
layer. An additional advantage of SNR scalability is its ability to provide high degree of resilience to transmission errors
as the more important data of the lower layer can be sent over channel with better error performance, while the less
critical enhancement layer data can be sent over a channel with poor error performance.
Intro. 4.2.3 Temporal scalable extension
Temporal scalability is a tool intended for use in a range of diverse video applications from telecommunications
to HDTV for which migration to higher temporal resolution systems from that of lower temporal resolution systems may
be necessary. In many cases, the lower temporal resolution video systems may be either the existing systems or the less
expensive early generation systems, with the motivation of introducing more sophisticated systems gradually. Temporal
scalability involves partitioning of video frames into layers, whereas the lower layer is coded by itself to provide the
basic temporal rate and the enhancement layer is coded with temporal prediction with respect to the lower layer, these
layers when decoded and temporal multiplexed to yield full temporal resolution of the video source. The lower temporal
resolution systems may only decode the lower layer to provide basic temporal resolution, whereas more sophisticated
systems of the future may decode both layers and provide high temporal resolution video while maintaining
interworking with earlier generation systems. An additional advantage of temporal scalability is its ability to provide
resilienc
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