ISO/IEC 23001-18:2022
(Main)Information technology — MPEG systems technologies — Part 18: Event message track format for the ISO base media file format
Information technology — MPEG systems technologies — Part 18: Event message track format for the ISO base media file format
This document specifies the format of the event message track.
Technologies de l'information — Technologies des systèmes MPEG — Partie 18: Format de la piste du message d'événement pour le format ISO de base pour les fichiers médias
General Information
Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 23001-18
First edition
2022-06
Information technology — MPEG
systems technologies —
Part 18:
Event message track format for the
ISO base media file format
Technologies de l'information — Technologies des systèmes MPEG —
Partie 18: Format de la piste du message d'événement pour le format
ISO de base pour les fichiers médias
Reference number
ISO/IEC 23001-18:2022(E)
© ISO/IEC 2022
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ISO/IEC 23001-18:2022(E)
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© ISO/IEC 2022 – All rights reserved
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ISO/IEC 23001-18:2022(E)
Contents Page
Foreword ........................................................................................................................................................................................................................................iv
1 Scope ................................................................................................................................................................................................................................. 1
2 Normative references ..................................................................................................................................................................................... 1
3 Terms, definitions, abbreviated terms and notations ................................................................................................. 1
3.1 Terms and definitions ...................................................................................................................................................................... 1
3.2 Abbreviated terms .............................................................................................................................................................................. 2
3.3 Notation ........................................................................................................................................................................................................ 2
4 General ........................................................................................................................................................................................................................... 2
5 Background ............................................................................................................................................................................................................... 2
6 Event message track structure .............................................................................................................................................................3
6.1 EventMessageInstanceBox ........................................................................................................................................................... 3
6.1.1 Definition .................................................................................................................................................................................. 3
6.1.2 Syntax ........................................................................................................................................... ................................................ 3
6.1.3 Semantics .................................................................................................................................................................................. 3
6.2 EventMessageEmptyBox .................................................................................................................................................................... 3
7 Event message track format ....................................................................................................................................................................3
7.1 Track format ............................................................................................................................................................................................. 3
7.2 Sample entry format .......................................................................................................................................................................... 4
7.3 Scheme identifier list box .............................................................................................................................................................. 4
7.3.1 Definition .................................................................................................................................................................................. 4
7.3.2 Syntax ........................................................................................................................................... ................................................ 4
7.3.3 Semantics .................................................................................................................................................................................. 4
7.4 Sample format ......................................................................................................................................................................................... 4
7.5 Codecs parameter ................................................................................................................................................................................ 5
8 Timing constraints ............................................................................................................................................................................................5
9 Processing ...................................................................................................................................................................................................................5
9.1 Client processing ...................................................................... ............................................................................................................. 5
9.2 Conversion of DASHEventMessageBox to EventMessageInstanceBox .................................................... 6
9.2.1 General ........................................................................................................................................................................................ 6
9.2.2 Example 1: Algorithm for finding sample boundaries in a segment of [T,T+D) .......... 6
9.2.3 Example 2: Algorithm for finding the samples and the sample contents ........................ 7
9.3 Track conversion ................................................................................................................................................................................... 7
9.3.1 General ........................................................................................................................................................................................ 7
9.3.2 De-multiplex a CMAF track file with DASHEventMessageBoxes .................................................. 7
9.3.3 Multiplex a CMAF track file with DASHEventMessageBoxes ........................................................... 8
9.3.4 Fragmentation and de-fragmentation of event message tracks .............................................. 8
9.4 Examples ...................................................................................................................................................................................................... 9
9.4.1 General ........................................................................................................................................................................................ 9
9.4.2 Example 5: Input list of DASH event messages events ...................................................................... 9
Bibliography .............................................................................................................................................................................................................................10
iii© ISO/IEC 2022 – All rights reserved
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ISO/IEC 23001-18:2022(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 23001 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 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO/IEC 23001-18:2022(E)
Information technology — MPEG systems technologies —
Part 18:
Event message track format for the ISO base media file
format
1 Scope
This document specifies the format of the event message track.
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 14496-12, Information technology — Coding of audio-visual objects — Part 12: ISO base media file
formatISO/IEC 23009-1, Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1:
Media presentation description and segment formats3 Terms, definitions, abbreviated terms and notations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1.1
active event
event (3.1.2) with a start time up to start time plus duration overlapping the current media time
3.1.2event
aperiodic sparse metadata information that is intended for a specific interval of media-time
3.1.3event duration
duration when the event (3.1.2) is applicable
3.1.4
event instance
representation of the event (3.1.2) in the track represented by an event message instance box
3.1.5event start time
start of the interval in media-time when event information is applicable
© ISO/IEC 2022 – All rights reserved
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ISO/IEC 23001-18:2022(E)
3.1.6
event message track
ISO base media file format timed metadata track that carries event messages
3.2 Abbreviated terms
DASH dynamic adaptive streaming over HTTP, as specified in ISO/IEC 23009-1
ISO-BMFF ISO base media file format, as specified in ISO/IEC 14496-12
3.3 Notation
For the purposes of this document, the notation used in ISO/IEC 23009-1 applies.
4 General
The DASHEventMessageBox, defined in ISO/IEC 23009-1, is a box structure that may be used in streaming
applications. Since it is a top-level box and has its own timeline, it is tricky to work within ISO-BMFF
formatted media files, such as those based on the common media application format (CMAF) (see
ISO/IEC 23000-19). For instance, identifying active events at any point in the media track may require
scanning of a large part of that track. In addition, it is not clear what happens to DASHEventMessageBoxes
when tracks are de-fragmented. Further, DASHEventMessageBoxes cannot be de-multiplexed from track
files based on ISO/IEC 23009-1 or ISO/IEC 23000-19.This document specifies the event message track format for the carriage of event messages in tracks of
the ISO base media file format (ISO-BMFF) ISO/IEC 14496-12. This event message track format associates
the timeline of the newly defined event message instance box to the track timeline. The specified
track format enables all common ISO-BMFF processing such as multiplexing and de-fragmentation. In
addition, multiplexing and de-multiplexing operations using top-level DASHEventMessageBox based on
this event message track format are defined. The carriage in the event message track format makes this
information more easily accessible to devices that can seek through ISO-BMFF formatted media files.
The event message track format is defined in the following clauses.5 Background
In CMAF track files and DASH segments DASHEventMessageBoxes may occur as top-level boxes as defined
in ISO/IEC 23000-19 and ISO/IEC 23009-1. The DASHEventMessageBox arises in two versions as defined
in ISO/IEC 23009-1:aligned(8) class DASHEventMessageBox
extends FullBox('emsg', version, flags = 0){
if (version==0) {
string scheme_id_uri;
string value;
unsigned int(32) timescale;
unsigned int(32) presentation_time_delta;
unsigned int(32) event_duration;
unsigned int(32) id;
else if (version==1) {
unsigned int(32) timescale;
unsigned int(64) presentation_time;
unsigned int(32) event_duration;
unsigned int(32) id;
string scheme_id_uri;
string value;
unsigned int(8) message_data[];
The semantics are defined in ISO/IEC 23009-1.
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ISO/IEC 23001-18:2022(E)
6 Event message track structure
6.1 EventMessageInstanceBox
6.1.1 Definition
The EventMessageInstanceBox is defined to enable carriage of the information contained in
DASHEventMessageBoxes in tracks. This box is very similar to the DASHEventMessageBox defined in
ISO/IEC 23009-1 but instead occurs only in samples of a track.6.1.2 Syntax
aligned(8) class EventMessageInstanceBox
extends FullBox('emib', version, flags = 0){
unsigned int(32) reserved = 0;
signed int(64) presentation_time_delta;
unsigned int(32) event_duration;
unsigned int(32) id;
string scheme_id_uri;
string value;
unsigned int(8) message_data[];
6.1.3 Semantics
The semantics of all fields except the following are defined in ISO/IEC 23009-1 for the
DASHEventMessageBox:— presentation_time_delta provides the event start time on the media presentation timeline relative
to the presentation time of the sample enclosing the EventMessageInstanceBox.— The presentation_time_delta and event_duration values are in the number of ticks in the timescale
defined in the track’s MediaHeaderBox.NOTE A DASHEventMessageBox can be converted to one or more EventMessageInstanceBoxes to enable
carriage in ISO-BMFF samples based on this document. An example algorithm is given in 9.2.
6.2 EventMessageEmptyBoxaligned(8) class EventMessageEmptyBox extends Box('emeb')
The EventMessageEmptyBox is defined to signal duration when no event is active, with the
following semantics. The box is empty, and the duration is defined by the sample enclosing the
EventMessageEmptyBox.NOTE Using zero-size samples to signal when no event metadata or event is active is avoided because this
can cause problems in some devices.7 Event message track format
7.1 Track format
EventMessageInstanceBoxes shall be carried in ISO-BMFF timed
...
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