ISO/IEC 23000-19:2020

INTERNATIONAL ISO/IEC
STANDARD 23000-19
Second edition
2020-03
Information technology — Multimedia
application format (MPEG-A) —
Part 19:
Common media application format
(CMAF) for segmented media
Technologies de l'information — Format pour application multimédia
(MPEG-A) —
Partie 19: Format CMAF (Common Media Application Format) pour
médias segmentés
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
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ii © ISO/IEC 2020 – All rights reserved

Contents Page
Foreword .vii
Introduction .viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Media objects . 3
3.2 Logical structure . 3
3.3 Application model . 4
4 Abbreviated terms . 6
5 Document organization . 8
6 CMAF hypothetical application model, media object model and profiles .10
6.1 Overview of the hypothetical application model and media object model .10
6.2 CMAF content processing model .11
6.3 Late binding CMAF track synchronization .12
6.4 Adaptive switching of CMAF tracks in CMAF switching sets .13
6.5 CMAF specified objects and profiles.14
6.5.1 Object derivation and interoperability code points .14
6.5.2 Encoded media objects . .14
6.5.3 Logical media object sets .14
6.5.4 Addressable media objects .14
6.5.5 CMAF profiles, brand and identifiers .15
6.6 CMAF media object model .16
6.6.1 CMAF fragments .16
6.6.2 CMAF tracks .17
6.6.3 CMAF track files .17
6.6.4 CMAF segments . .18
6.6.5 CMAF chunks . .18
6.6.6 CMAF switching sets and adaptive switching .19
6.6.7 CMAF selection sets and late binding .22
6.6.8 CMAF presentation timing model .23
6.6.9 Manifest information.26
6.6.10 CMAF addressable media objects, resources, and resource identifiers .26
7 CMAF track format .27
7.1 Overview .27
7.2 CMAF brands.27
7.3 CMAF media objects .28
7.3.1 CMAF boxes .28
7.3.2 CMAF track media objects .30
7.3.3 CMAF addressable media objects .34
7.3.4 CMAF switching sets .36
7.3.5 CMAF selection sets . .39
7.3.6 CMAF presentations .39
7.4 Additional boxes, not defined in the ISO Base Media File Format .40
7.4.1 Track Encryption Box ('tenc') .40
7.4.2 Sample Encryption Box ('senc') . .40
7.4.3 Protection System Specific Header Box ('pssh') .40
7.4.4 Media profile specific boxes .40
7.4.5 Event Message Box ('emsg') .40
7.5 Constraints on ISO Base Media File Format boxes .41
7.5.1 Movie Header Box ('mvhd') .41
7.5.2 Metadata Boxes .41
7.5.3 Kind Box ('kind') .41
© ISO/IEC 2020 – All rights reserved iii

7.5.4 Track Header Box ('tkhd') .42
7.5.5 Media Header Box ('mdhd') .42
7.5.6 Video Media Header Box ('vmhd') .42
7.5.7 Sound Media Header Box ('smhd') .43
7.5.8 Subtitle Media Header Box ('sthd') .43
7.5.9 Data Reference Box ('dref') .43
7.5.10 Sample Description Box ('stsd') .43
7.5.11 Protection Scheme Information Box ('sinf') .43
7.5.12 Track contained media sample information boxes .43
7.5.13 Edit List Box ('elst') .44
7.5.14 Track Extends Box ('trex') .44
7.5.15 Movie Fragment Header Box ('mfhd') .44
7.5.16 Track Fragment Header Box ('tfhd') .44
7.5.17 Track Run Box ('trun') .45
7.5.18 Sample Group Description Box ('sgpd') .45
7.5.19 Media Data Box ('mdat') .45
7.5.20 Sub-sample Information Box ('subs') .46
7.6 The Structural CMAF Brand 'cmfc' .46
7.7 The structural CMAF Brand 'cmf2' .46
7.7.1 General.46
7.7.2 Edit List Box ('elst') .46
7.7.3 Track Run Box ('trun') .46
8 Common encryption of CMAF tracks .46
8.1 Multiple DRM system support .46
8.2 Track encryption .47
8.2.1 General requirements .47
8.2.2 CMAF track constraints .48
8.2.3 Encryption constraints .49
8.2.4 CMAF presentation encryption .50
9 Video CMAF tracks .50
9.1 Overview .50
9.2 General video CMAF track format .51
9.2.1 General video CMAF track structure and constraints .51
9.2.2 Video Media Header ('vmhd') .51
9.2.3 Track Header Box ('tkhd') .52
9.2.4 Sample Description Box ('stsd') .52
9.2.5 Video CMAF fragment presentation time .53
9.2.6 Video media sample dependencies .53
9.2.7 Video edit lists .53
9.2.8 General video CMAF fragment random access constraints.53
9.2.9 Additional random access pictures within CMAF video fragments .53
9.2.10 Image framing and encoding constraints .54
9.2.11 General video CMAF switching set constraints .54
9.3 NAL structured video CMAF tracks .55
9.3.1 Overview .55
9.3.2 CMAF track format constraints for NAL structured video .56
9.3.3 NAL structured video access units contained in media samples .57
9.3.4 NAL structured video coding sequences corresponding to CMAF fragments .57
9.3.5 Elementary stream constraints .58
9.3.6 General CMAF switching set constraints for NAL structured video .58
9.3.7 Single initialization CMAF switching set constraints for NAL structured
video tracks and media profiles .58
9.4 AVC video CMAF tracks .59
9.4.1 Storage of AVC elementary streams .59
9.4.2 Constraints on AVC elementary streams .60
9.5 AVC video Internet Media Type parameters .61
9.5.1 AVC signalling of "codecs" parameters .61
iv © ISO/IEC 2020 – All rights reserved

10 Audio CMAF tracks .62
10.1 Overview .62
10.2 General audio CMAF track format .62
10.2.1 Derivation .62
10.2.2 Track Header Box ('tkhd') .62
10.2.3 Sound Media Header Box ('smhd') .63
10.2.4 Sample Description Box ('stsd') .63
10.2.5 AudioSampleEntry .63
10.2.6 Audio offset edit list .63
10.3 AAC audio CMAF tracks .63
10.3.1 Overview .63
10.3.2 "codecs" parameter signalling .63
10.3.3 Considerations for AAC audio encoding .64
10.3.4 AAC track constraints .65
10.3.5 AAC elementary stream constraints .66
10.4 AAC core audio CMAF media profile .67
10.5 AAC adaptive switching audio CMAF media profile .67
10.5.1 General constraints .67
10.5.2 CMAF fragment encoding constraints .68
10.5.3 General considerations and requirements .68
10.5.4 Constraints for AAC-LC .68
10.5.5 Constraints for HE-AAC .69
10.5.6 Constraints for HE-AACv2 .70
11 Subtitles and captions .71
11.1 Overview .71
11.2 WebVTT .71
11.3 IMSC text and image tracks .72
11.3.1 General.72
11.3.2 Common constraints .72
11.3.3 IMSC1 text track constraints .73
11.3.4 IMSC1 image track constraints .73
11.4 CTA-608 and CTA-708 .73
11.5 Metadata for subtitles .74
12 CMAF media profiles and CMAF presentation profiles .74
12.1 CMAF media profiles .74
12.1.1 General guidelines for specifying CMAF media profiles .74
12.1.2 Guidelines for audio CMAF media profiles .75
12.1.3 Guidelines for video CMAF media profiles .75
12.2 CMAF presentation profiles .76
12.2.1 General.76
12.2.2 CMAF profile conformance .76
Annex A (normative) CMAF presentation profiles, media profiles and supplemental data .79
Annex B (normative) HEVC video CMAF track format and CMAF media profiles .83
Annex C (informative) Subsampling of NAL structured video tracks in CMAF switching sets .88
Annex D (informative) Hypothetical player model .98
Annex E (informative) Event messages .101
Annex F (informative) Error handling for missing media .102
Annex G (informative) Recommendations for AAC CMAF switching set encoding .103
Annex H (normative) Scalable HEVC media profile and track format .106
Annex I (normative) AAC multichannel CMAF media profiles and track format .112
Annex J (normative) MPEG-H 3D audio track format and CMAF media profile .115
Annex K (normative) MPEG-D USAC track format and CMAF media profile .120
© ISO/IEC 2020 – All rights reserved v

Annex L (normative) IMSC 1.1 media profiles .122
Bibliography .124
vi © ISO/IEC 2020 – All rights reserved

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).
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 http:// 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.
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.
This second edition cancels and replaces the first edition (ISO/IEC 23000-19:2018), which has been
technically revised. It also incorporates the Amendments ISO/IEC 23000-19:2018/Amd.1:2018 and
ISO/IEC 23000-19:2018/Amd.2:2019.
The main changes compared to the previous edition are as follows:
— addition of supplemental data brands;
— modification to the structural brand cmfc for compatibility with DASH segments;
— definition of a stricter brand 'cmf2' for legacy devices;
— refinements and updates to HEVC media profiles for SDR and HDR;
— definition of the scalable HEVC media profile;
— definition of AAC multichannel media profiles;
— definition of MPEG-H 3D audio track format and CMAF media profile;
— definition of MPEG-D USAC track format and CMAF media profile;
— definition of IMSC1.1 media profile.
A list of all parts in the ISO/IEC 23000 series can be found on the ISO website.
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.
© ISO/IEC 2020 – All rights reserved vii

Introduction
Common media application format (CMAF) combines and constrains several MPEG specifications to
define a multimedia format that is optimized for delivery of a single adaptive multimedia presentation
to a variety of devices, using a variety of adaptive streaming, broadcast, download and storage methods.
Several MPEG specifications have been adopted for much of the video delivered over the internet and
other IP networks (cellular, cable, broadcast, etc.). Various organizations have taken MPEG’s core coding,
file format and system standards and combined them into their own specifications for their specific
application. While these specifications are similar, their differences result in unnecessary duplication
of engineering effort and duplication of identical content in slightly different formats, which results in
increased storage and delivery costs.
CMAF provides a common media specification that application specifications, such as MPEG dynamic
adaptive streaming over HTTP (DASH), can reference and a common media format that allows a single
encoded multimedia presentation to be used by many applications.
viii © ISO/IEC 2020 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 23000-19:2020(E)
Information technology — Multimedia application format
(MPEG-A) —
Part 19:
Common media application format (CMAF) for
segmented media
1 Scope
This document specifies the CMAF multimedia format, which contains segmented media objects
optimized for streaming delivery and decoding on end user devices in adaptive multimedia
presentations.
CMAF specifies a track format derived from the ISO base media file format, then derives addressable
media objects from CMAF tracks that can be used for storage and delivery.
CMAF specifies sets of tracks that share encoding and packaging constraints that enable the selection
of multiple tracks to form a multimedia presentation and allow seamless switching of alternative
encodings of the same content at different bit rates, frame rates, resolution, etc.
CMAF specifies a hypothetical application model that determines how tracks in a CMAF presentation
are intended to be combined and synchronized to form a multimedia presentation. The model abstracts
delivery to allow any delivery method. The hypothetical application model assumes a manifest and
player, but CMAF does not specify a manifest, player, or delivery protocol, with the intent that any that
support the hypothetical application model can be used.
CMAF specifies media profiles and brands that constrain media encoding and packaging of CMAF
tracks to enable seamless adaptive switching of tracks and allow devices to identify compatible content
by its brand.
CMAF specifies presentation profiles that conditionally require sets of CMAF tracks conforming to
specified media profiles and allow content creators and devices to identify compatible multimedia
presentations.
CMAF enables extensibility by specifying how new media profiles and presentation profiles can be
specified and identified and includes guidelines for those specifications.
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 14496-1, Information technology — Coding of audio-visual objects — Part 1: Systems
ISO/IEC 14496-3, Information technology — Coding of audio-visual objects — Part 3: Audio
ISO/IEC 14496-10, Information technology — Coding of audio-visual objects — Part 10: Advanced
video coding
ISO/IEC 14496-12, Information technology — Coding of audio-visual objects — Part 12: ISO base media
file format
ISO/IEC 14496-14, Information technology — Coding of audio-visual objects — Part 14: MP4 file format
© ISO/IEC 2020 – All rights reserved 1

ISO/IEC 14496-15, Information technology — Coding of audio-visual objects — Part 15: Carriage of
network abstraction layer (NAL) unit structured video in the ISO base media file format
ISO/IEC 14496-30, Information technology — Coding of audio-visual objects — Part 30: Timed text and
other visual overlays in ISO base media file format
ISO/IEC 23001-7, Information technology — MPEG systems technologies — Part 7: Common encryption in
ISO base media file format files
ISO/IEC 23008-2, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 2: High efficiency video coding
ISO/IEC 23009-1, Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1:
Media presentation description and segment formats
ISO/IEC 23008-3:2019,Information technology — High efficiency coding and media delivery in
heterogeneous environments — Part 3: 3D audio
ISO/IEC 23091-3, Information technology — Coding-independent code points — Part 3: Audio
ISO/IEC 23003-4:2015, MPEG audio technologies — Part 4: Dynamic range control
ISO/IEC 23003-3:2012, Information technology — MPEG audio technologies — Part 3: Unified speech and
audio coding
IETF RFC 5234, Augmented BNF for Syntax Specifications: ABNF, ht t p s:// t o ol s . ie t f . or g / ht m l/ r f c 523 4
IETF RFC 6381:2011, The ‘Codecs’ and ‘Profiles’ Parameters for “Bucket” Media Types, ht t p s:// t o ol s . ie t f
. or g / ht m l/ r f c 6381
ITU-R Recommendation BT.709, Parameter values for the HDTV standards for production and international
programme exchange
ITU-R Recommendation BT.1886, Reference electro-optical transfer function for flat panel displays used in
HDTV studio production
ITU-R Recommendation BT.2035, A reference viewing environment for evaluation of HDTV program
material or completed programmes
ITU-T Recommendation X.667:2014, Information technology — Open Systems Interconnection —
Procedures for the operation of OSI Registration Authorities: Generation and registration of Universally
Unique Identifiers (UUIDs) and their use as ASN.1 object identifier components, ht t p s:// w w w .it u .i nt/ r e c/ T
-R EC -X . 6 67
ANSI/CTA-608-E R-2014, Line 21 Data Services, ht t p:// w w w .t e c h s t r e e t . c om/ s t a nd a r d s/ c t a - 6 0 8 - e -r2014
? pr o duc t _ id = 1815 4 47
ANSI/CTA-708-E, Digital Television (DTV) Closed Captioning, http:// www .techstreet .com/ standards/ cta
-70 8 - e ? pr o duc t _ id = 18 6 035 4
W3C IMSC1, TTML Profiles for Internet Media Subtitles and Captions 1.0, http:// www .w3 .org/ TR/
ttml -imsc1
W3C IMSC1.1, TTML Profiles for Internet Media Subtitles and Captions 1.1, ht t p:// w w w .w3 . or g / T R / t t m l
-i m s c1 .1
W3C, TTML Media Type Definition and Profile Registry, W3C Working Group Note, ht t p s:// w w w .w3 . or g /
TR/ ttml -profile -registry
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2 © ISO/IEC 2020 – All rights reserved

ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1 Media objects
3.1.1
CMAF fragment
encoded ISO BMFF media segment conforming to CMAF constraints
3.1.2
CMAF header
sequence of CMAF constrained ISO BMFF boxes that do not reference any media samples (3.3.15), but
are associated with a CMAF track (3.2.1) and necessary for the decoding of its CMAF fragments (3.1.1)
3.1.3
CMAF addressable media object
CMAF media object packaged for storage or delivery
Note 1 to entry: Examples include a CMAF track file (3.1.6) containing a CMAF header (3.1.2) and CMAF fragments
(3.1.1), or a CMAF segment (3.1.5) containing one or more CMAF fragments, or a CMAF chunk (3.1.4) containing a
partial sequence of the media samples (3.3.15) of a CMAF fragment.
3.1.4
CMAF chunk
CMAF media object that contains a consecutive subset of the media samples (3.3.15) of a CMAF fragment
(3.1.1), where only the first CMAF chunk of a CMAF fragment is constrained to be an adaptive switching
(3.3.9) point
3.1.5
CMAF segment
CMAF addressable media object (3.1.3) consisting of one or more consecutive CMAF fragments (3.1.1)
from the same CMAF track (3.2.1)
Note 1 to entry: A “CMAF segment” is conformant to an “ISO BMFF segment” and a “DASH segment”.
3.1.6
CMAF track file
one CMAF track (3.2.1) stored consecutively in a single ISO BMFF file with the earliest CMAF fragment
(3.1.1) constrained to start at decode time zero
3.2 Logical structure
3.2.1
CMAF track
sequence of CMAF fragments (3.1.1) that are consecutive in presentation time, contain one media
stream, conform to at least one structural CMAF brand, together with an associated CMAF header
(3.1.2) that can initialize playback
3.2.2
CMAF switching set
set of one or more CMAF tracks (3.2.1), where each track is an alternative encoding of the same source
content, and are constrained to enable seamless track switching (3.3.9)
3.2.3
aligned CMAF switching set
set of CMAF switching sets (3.2.2), the CMAF tracks (3.2.1) of which all contain alternative encodings of
the same source content in time-aligned CMAF fragments (3.1.1), but all CMAF tracks do not conform to
a single CMAF switching set
© ISO/IEC 2020 – All rights reserved 3

3.2.4
CMAF selection set
set of one or more CMAF switching sets (3.2.2), where each CMAF switching set encodes an alternative
aspect of the same presentation over the same time period, only one of which is intended to be played at
a time, e.g., an alternative language or codec
3.2.5
CMAF presentation
set of one or more CMAF selection sets (3.2.4) that can be simultaneously decoded to produce a
multimedia user experience, potentially including synchronized audio, video, and subtitles
3.2.6
CMAF media profile
encoding constraint on a CMAF track (3.2.1) and its contained media samples (3.3.15) associated with a
CMAF structural brand
3.2.7
CMAF presentation profile
requirement on the CMAF media profiles (3.2.6) contained in a CMAF presentation (3.2.5)
3.2.8
required media profile
CMAF media profile (3.2.6) conditionally required by a CMAF presentation profile (3.2.7)
3.2.9
manifest
document describing one or more CMAF presentations (3.2.5)
Note 1 to entry: Manifest formats are not specified in this document.
3.2.10
audio programme
complete collection of all audio programme components and, if present, a set of accompanying presets
3.2.11
audio programme component
smallest addressable unit of an audio programme
3.2.12
CMAF supplemental data
data that can be present in a CMAF track (3.2.1) and its contained media samples (3.3.15) conformant to
a set of requirements identified by a brand
3.2.13
CMAF structural brand
four-character code used in brand-signaling boxes to indicate compliance to box-level constraints as
opposed to media-level constraints
3.3 Application model
3.3.1
CMAF hypothetical application model
CMAF presentation (3.2.5) application model based on late binding (3.3.3) and synchronization of CMAF
tracks (3.2.1) that partly determines the CMAF track encoding constraints necessary for an intended
CMAF presentation
3.3.2
player
component of the CMAF hypothetical application model (3.3.1) responsible for interpreting a manifest
(3.2.9), requesting resources, and rendering a CMAF presentation (3.2.5)
4 © ISO/IEC 2020 – All rights reserved

3.3.3
late binding
selection (3.3.8) and synchronization of separately stored CMAF tracks (3.2.1) by a player (3.3.2)
resulting in a synchronized multimedia presentation
3.3.4
CMAF presentation timeline
timeline shared by all CMAF tracks (3.2.1) in a CMAF presentation (3.2.5), starting at CMAF presentation
time zero, which is coincident with the earliest media samples (3.3.15) intended for presentation
3.3.5
presentation time offset
earliest presentation time of each CMAF track (3.2.1) at the start of a CMAF presentation (3.2.5)
Note 1 to entry: Presentation time offset is an encoded property of tracks in a presentation, but it can also refer
to that value stored in a manifest (3.2.9).
3.3.6
CMAF fragment duration
sum of the media sample (3.3.15) durations documented in the TrackFragmentRunBox of all
MovieFragmentHeaderBoxes in the CMAF fragment (3.1.1)
3.3.7
CMAF presentation duration
sum of the CMAF fragment durations (3.3
...