ISO/IEC 23001-18:2022

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

• Status: Published
• Publication Date: 06-Jun-2022
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29/WG 3 - MPEG Systems
• Current Stage: 6060 - International Standard published
• Start Date: 07-Jun-2022
• Due Date: 27-Jul-2022
• Completion Date: 07-Jun-2022

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)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2022

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

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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

format

ISO/IEC 23009-1, Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1:

Media presentation description and segment formats
3 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

3.1.2
event

aperiodic sparse metadata information that is intended for a specific interval of media-time

3.1.3
event 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

3.1.5
event 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 EventMessageEmptyBox
aligned(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
...