ISO/IEC 23000-19:2024

Information technology - Multimedia application format (MPEG-A) - Part 19: Common media application format (CMAF) for segmented media

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.

Technologies de l'information — Format pour application multimédia (MPEG-A) — Partie 19: Format CMAF (Common Media Application Format) pour médias segmentés

General Information

• Status: Published
• Publication Date: 28-Feb-2024
• 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 - Coding of audio, picture, multimedia and hypermedia information
• Current Stage: 6060 - International Standard published
• Start Date: 29-Feb-2024
• Due Date: 02-Mar-2024
• Completion Date: 29-Feb-2024

Relations

• Amended By: ISO/IEC 23000-19:2024/Amd 1:2024 - Information technology - Multimedia application format (MPEG-A) - Part 19: Common media application format (CMAF) for segmented media - Amendment 1: Low complexity enhancement video Coding (LCEVC) and other technologies
• Effective Date: 24-Sep-2022
• Revises: ISO/IEC 23000-19:2020 - Information technology - Multimedia application format (MPEG-A) - Part 19: Common media application format (CMAF) for segmented media
• Effective Date: 17-Sep-2022
• Revises: ISO/IEC 23000-19:2020/Amd 1:2021 - Information technology - Multimedia application format (MPEG-A) - Part 19: Common media application format (CMAF) for segmented media - Amendment 1: Additional CMAF HEVC media profiles
• Effective Date: 17-Sep-2022

Overview

ISO/IEC 23000-19:2024 - Part 19 of the MPEG‑A series - defines the Common Media Application Format (CMAF) for segmented media. The standard specifies a CMAF track format derived from the ISO base media file format and defines how those tracks are turned into addressable media objects optimized for streaming delivery and decoding on end‑user devices in adaptive multimedia presentations. CMAF focuses on enabling seamless switching between alternative encodings (different bitrates, frame rates, resolutions) while remaining delivery‑agnostic: it assumes a manifest and player model but does not mandate a manifest format, player implementation, or delivery protocol.

Key technical topics and requirements

• CMAF track format: A track structure built on the ISO base media file format with defined boxes and constraints for consistent packaging.
• Addressable media objects: Rules for deriving storage- and delivery-ready objects from CMAF tracks.
• Switching sets and adaptive switching: Groups of tracks with shared encoding and packaging constraints that enable seamless switching between encodings.
• Media profiles, brands and presentation profiles: Identifiers and constraints that allow devices and content to detect compatibility and enable interoperable adaptive playback.
• Hypothetical application model: An abstract model for combining and synchronizing tracks into a multimedia presentation while remaining independent of delivery protocols.
• Late binding synchronization: Mechanisms for synchronizing tracks at playback time to support flexible assembly of presentations.
• CMAF fragments, segments and chunks: Structural elements that support segmented media delivery and reduced startup/seek times.
• Common encryption support: Guidance for multiple‑DRM system support and constrained encryption of CMAF tracks to enable interoperable protected delivery.
• Extensibility guidelines: Procedures for defining and identifying new media and presentation profiles.

Practical applications and who uses this standard

CMAF is intended for organizations implementing adaptive streaming workflows and device playback ecosystems:

• OTT service providers and content distributors - for packaging multi-bitrate, multi‑resolution assets for adaptive streaming.
• Encoder/transcoder and packaging vendors - to produce CMAF‑compliant track files and addressable objects.
• Player and device manufacturers - to detect CMAF brands/profiles and implement seamless switching and synchronization.
• CDNs and storage providers - for efficient segmented delivery and object addressing.
• DRM and security vendors - to implement common encryption patterns compatible with CMAF.

Benefits include interoperability across ecosystems, predictable adaptive switching behavior, and a standardized path from encoded tracks to delivery objects.

Related standards

• ISO base media file format (basis for CMAF track structure)
• MPEG‑A family / ISO/IEC 23000 series (other parts in the multimedia application format suite)

Keywords: ISO/IEC 23000-19:2024, CMAF, Common Media Application Format, segmented media, adaptive streaming, media profiles, switching sets, track format, common encryption.

Standards Content (Sample)

International
Standard
ISO/IEC 23000-19
Third edition
Information technology —
2024-02
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 2024
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 copyright office
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Published in Switzerland
© ISO/IEC 2024 – All rights reserved
ii
Contents Page
Foreword .vii
Introduction .viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 3
3.1 Media objects .3
3.2 Logical structure .3
3.3 Application model .5
4 Abbreviated terms . 6
5 Document organization . 9
6 CMAF hypothetical application model, media object model and profiles . 9
6.1 Overview of the hypothetical application model and media object model.9
6.2 CMAF content processing model .10
6.3 Late binding CMAF track synchronization .11
6.4 Adaptive switching of CMAF tracks in CMAF switching sets . 12
6.5 CMAF specified objects and profiles . 13
6.5.1 Object derivation and interoperability code points . 13
6.5.2 Encoded media objects . 13
6.5.3 Logical media object sets . 13
6.5.4 Addressable media objects . 13
6.5.5 CMAF profiles, brand and identifiers .14
6.6 CMAF media object model . 15
6.6.1 CMAF fragments . 15
6.6.2 CMAF tracks .16
6.6.3 CMAF track files .16
6.6.4 CMAF segments .17
6.6.5 CMAF chunks .17
6.6.6 CMAF switching sets and adaptive switching .18
6.6.7 CMAF selection sets and late binding .21
6.6.8 CMAF presentation timing model . 22
6.6.9 Manifest information . . .24
6.6.10 CMAF addressable media objects, resources, and resource identifiers . .24
7 CMAF track format .25
7.1 Overview . 25
7.2 CMAF brands . 25
7.3 CMAF media objects .27
7.3.1 CMAF boxes .27
7.3.2 CMAF track media objects . 29
7.3.3 CMAF addressable media objects . 34
7.3.4 CMAF switching sets . 35
7.3.5 CMAF selection sets . 38
7.3.6 CMAF presentations . 38
7.4 Additional boxes, not defined in the ISO Base Media File Format . 39
7.4.1 Track Encryption Box ('tenc') . 39
7.4.2 Sample Encryption Box ('senc'). 39
7.4.3 Protection System Specific Header Box ('pssh') . 39
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 . 40
7.5.1 Movie Header Box ('mvhd') . 40
7.5.2 Metadata Boxes. 40
7.5.3 Kind Box ('kind') .41

© ISO/IEC 2024 – All rights reserved
iii
7.5.4 Track Header Box ('tkhd') .41
7.5.5 Media Header Box ('mdhd') .41
7.5.6 Video Media Header Box ('vmhd') .42
7.5.7 Sound Media Header Box ('smhd') .42
7.5.8 Subtitle Media Header Box ('sthd') .42
7.5.9 Data Reference Box ('dref') .42
7.5.10 Sample Description Box ('stsd') .42
7.5.11 Protection Scheme Information Box ('sinf') .42
7.5.12 Track contained media sample information boxes .42
7.5.13 Edit List Box ('elst') .43
7.5.14 Track Extends Box ('trex') .43
7.5.15 Movie Fragment Header Box ('mfhd') .43
7.5.16 Track Fragment Header Box ('tfhd') . 44
7.5.17 Track Run Box ('trun') . 44
7.5.18 Sample Group Description Box ('sgpd') . 44
7.5.19 Media Data Box ('mdat').45
7.5.20 Sub-sample Information Box ('subs') .45
7.6 The Structural CMAF Brand 'cmfc' .45
7.7 The structural CMAF Brand 'cmf2' .45
7.7.1 General .45
7.7.2 Edit List Box ('elst') .45
7.7.3 Track Run Box ('trun') .45
8 Common encryption of CMAF tracks .46
8.1 Multiple DRM system support . 46
8.2 Track encryption. 46
8.2.1 General requirements . 46
8.2.2 CMAF track constraints .47
8.2.3 Encryption constraints . 48
8.2.4 CMAF presentation encryption . 49
9 Video CMAF tracks .49
9.1 Overview . 49
9.2 General video CMAF track format . 50
9.2.1 General video CMAF track structure and constraints . . 50
9.2.2 Video Media Header ('vmhd') . 50
9.2.3 Track Header Box ('tkhd') .51
9.2.4 Sample Description Box ('stsd') .51
9.2.5 Video CMAF fragment presentation time .52
9.2.6 Video media sample dependencies . .52
9.2.7 Video edit lists .52
9.2.8 General video CMAF fragment random access constraints .52
9.2.9 Additional random access pictures within CMAF video fragments .52
9.2.10 Image framing and encoding constraints . 53
9.2.11 General video CMAF switching set constraints . 53
9.3 NAL structured video CMAF tracks . 54
9.3.1 Overview . 54
9.3.2 CMAF track format constraints for NAL structured video . 54
9.3.3 NAL structured video access units contained in media samples . 56
9.3.4 NAL structured video coding sequences corresponding to CMAF fragments . 56
9.3.5 Elementary stream constraints . 56
9.3.6 General CMAF switching set constraints for NAL structured video .57
9.3.7 Single initialization CMAF switching set constraints for NAL structured video
tracks and media profiles .57
9.4 AVC video CMAF tracks . 58
9.4.1 Storage of AVC elementary streams . 58
9.4.2 Constraints on AVC elementary streams . 58
9.5 AVC video Internet Media Type parameters . 60
9.5.1 AVC signalling of "codecs" parameters . 60
9.6 Video media profiles . 60

© ISO/IEC 2024 – All rights reserved
iv
10 Audio CMAF tracks . . 61
10.1 Overview .61
10.2 General audio CMAF track format .61
10.2.1 Derivation .61
10.2.2 Track Header Box ('tkhd') .61
10.2.3 Sound Media Header Box ('smhd') .62
10.2.4 Sample Description Box ('stsd') .62
10.2.5 AudioSampleEntry .62
10.2.6 Audio offset edit list .62
10.3 AAC audio CMAF tracks .62
10.3.1 Overview .62
10.3.2 "codecs" parameter signalling .62
10.3.3 Considerations for AAC audio encoding . 63
10.3.4 AAC track constraints . 64
10.3.5 AAC elementary stream constraints . 65
10.4 AAC core audio CMAF media profile . 66
10.5 AAC adaptive switching audio CMAF media profile .67
10.5.1 General constraints.67
10.5.2 CMAF fragment encoding constraints .67
10.5.3 General considerations and requirements .67
10.5.4 Constraints for AAC-LC . . . 68
10.5.5 Constraints for HE-AAC . 68
10.5.6 Constraints for HE-AACv2 .70
10.6 Audio media profiles .70
11 Subtitles and captions .70
11.1 Overview .70
11.2 WebVTT .71
11.3 IMSC text and image tracks .71
11.3.1 General .71
11.3.2 Common constraints . .71
11.3.3 IMSC1 text track constraints . 72
11.3.4 IMSC1 image track constraints . 72
11.4 CTA-608 and CTA-708 . 73
11.5 Metadata for subtitles . 73
11.6 Sparsity in Subtitle Tracks . 73
11.7 11.7 . .
Subtitle media profiles . 73
12 CMAF media profiles and CMAF presentation profiles .73
12.1 CMAF media profiles . 73
12.1.1 General guidelines for specifying CMAF media profiles . . 73
12.1.2 Guidelines for audio CMAF media profiles .74
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
13 Timed metadata tracks .77
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) Soure formats.91
Annex D (informative) Hypothetical player model .102
Annex E (informative) Event messages .105
Annex F (informative) Error handling for missing media .106
Annex G (informative) Recommendations for AAC CMAF switching set encoding .107

© ISO/IEC 2024 – All rights reserved
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Annex H (normative) Scalable HEVC media profile and track format .110
Annex I (normative) AAC multichannel CMAF media profiles and track format .116
Annex J (normative) MPEG-H 3D audio track format and CMAF media profile .119
Annex K (normative) MPEG-D USAC track format and CMAF media profile . 124
Annex L (normative) IMSC 1.1 media profiles .126
Annex M (normative) CMAF track and media profiles for VVC . 128
Annex N (normative) CMAF track and media profiles for EVC .138
Bibliography .142

© ISO/IEC 2024 – All rights reserved
vi
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
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ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
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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).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any
claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had not
received notice of (a) patent(s) which may be required to implement this document. However, implementers
are cautioned that this may not represent the latest information, which may be obtained from the patent
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responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
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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.
This third edition cancels and replaces the second edition (ISO/IEC 23000-19:2020), which has been
technically revised. It also incorporates the Amendment ISO/IEC 23000-19:2020/Amd.1:2021.
The main changes are as follows:
— addition of subclauses 9.6, 10.6 and 11.7,
— addition of Annexes M and N.
A list of all parts in the ISO/IEC 23000 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 2024 – 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.
Clause 6 provides a description of the objects and terminology specified, the CMAF object model, and
the hypothetical application model, which defines how these objects can be combined to form adaptive
multimedia presentations.
The specifications in Clauses 7 through Clause 12 are terse to facilitate development and testing and
assume an understanding of Clause 6. Clause 7 specifies ISO Base Media File Format boxes and structures
such as movie fragments and tracks that are used to construct all CMAF media objects. Clause 8 through
Clause 11 contain details specific to encryption, audio, video, and subtitle tracks. Clause 12 specifies the
combination of CMAF tracks and media profiles into CMAF presentations. It also recommends how to specify
additional CMAF media profiles and presentation profiles, which can be specified by other documents and
organizations.
CMAF presentation profiles and CMAF media profiles are specified in annexes to allow the addition of new
profiles without changing the core document. Additional informative annexes have been added to provide
explanations and recommendations on specific topics.

© ISO/IEC 2024 – All rights reserved
viii
International Standard ISO/IEC 23000-19:2024(en)
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 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 2024 – All rights reserved
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 23003-4:2020, Information technology — MPEG audio technologies — Part 4: Dynamic range control
ISO/IEC 23003-3, Information technology — MPEG audio technologies — Part 3: Unified speech and audio
coding
ISO/IEC 23008-2, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 2: High efficiency video coding
ISO/IEC 23008-3:2022, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 3: 3D audio
ISO/IEC 23009-1, Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media
presentation description and segment formats
ISO/IEC 23091-3, Information technology — Coding-independent code points — Part 3: Audio
ISO/IEC 23090-3, Information technology — Coded representation of immersive media — Part 3: Versatile video
coding
ISO/IEC 23094-1, Information technology — General video coding — Part 1: Essential video coding
1)
IETF RFC 5234, Augmented BNF for Syntax Specifications: ABNF
2)
IETF RFC 6381, The ‘Codecs’ and ‘Profiles’ Parameters for “Bucket” Media Types
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
3)
(UUIDs) and their use as ASN.1 object identifier components
ANSI/SCTE 214-1, MPEG DASH for IP-Based Cable Services Part 1: MPD Constraints and Extensions, https://
www .scte .org/ standards/ library/ catalog/ scte -214 -1 -mpeg -dash -for -ip -based -cable -services -part1 -mpd
-constraints -and -extensions/
W3C IMSC1, TTML Profiles for Internet Media Subtitles and Captions 1.0.1, https:// www .w3 .org/ TR/ ttml
-imsc1
W3C IMSC1.1, TTML Profiles for Internet Media Subtitles and Captions 1.1, https:// www .w3 .org/ TR/ ttml
-imsc1 .1
W3C WebVTT, The Web Video Text Tracks Format, Candidate Recommendation 4 April 2019 https:// www .w3
.org/ TR/ webvtt1/
W3C TTML Media Type Definition and Profile Registry, W3C Working Group Note, https:// www .w3 .org/ TR/
ttml -profile -registry
1) https:// tools .ietf .org/ html/ rfc5234
2) https:// tools .ietf .org/ html/ rfc6381
3) https:// www .itu .int/ rec/ T -REC -X .667

© ISO/IEC 2024 – All rights reserved
3 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 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 dec
...