ISO/IEC 23000-22:2025
(Main)Information technology — Multimedia application format (MPEG-A) — Part 22: Multi-image application format (MIAF)
Information technology — Multimedia application format (MPEG-A) — Part 22: Multi-image application format (MIAF)
This document specifies the Multi-Image Application Format (MIAF), which contains coded images, groups and sequences of images along with their metadata and the information about their relations to each other, all embedded in the High Efficiency Image File (HEIF) format. This document builds on ISO/IEC 23008-12 (HEIF) and specifies the following: — a set of additional constraints on ISO/IEC 23008-12 (HEIF), to simplify its file format options; — specific alpha plane formats; — a set of specific profiles and levels for the supported coding formats; — a set of specific metadata formats; — a set of brands, including application brands indicating conformance with specific profiles; — a set of rules for extending MIAF format to support additional coding formats, profiles, levels and metadata. This document also defines the normative behaviour for a MIAF reader and MIAF renderer. This document (MIAF) is intentionally written to be extensible, and to allow for forward compatibility. The format is also permissive of the presence of other data, such as coding formats, metadata, and derived images.
Technologies de l'information — Format pour application multimédia (MPEG-A) — Partie 22: Format pour application à images multiples (MIAF)
General Information
Relations
Standards Content (Sample)
International
Standard
ISO/IEC 23000-22
Second edition
Information technology —
2025-02
Multimedia application format
(MPEG-A) —
Part 22:
Multi-image application format
(MIAF)
Technologies de l'information — Format pour application
multimédia (MPEG-A) —
Partie 22: Format pour application à images multiples (MIAF)
Reference number
© ISO/IEC 2025
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© ISO/IEC 2025 – All rights reserved
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 4
5 Document organization and conventions . 4
6 MIAF concepts and processing of MIAF files . 4
6.1 General .4
6.2 MIAF data object model .5
6.3 MIAF image items .5
6.4 MIAF thumbnail image items .5
6.5 MIAF auxiliary image item .5
6.6 MIAF reader processing model .6
6.7 MIAF renderer processing model .8
7 MIAF file general requirements . 9
7.1 General .9
7.2 Box-level requirements .9
7.2.1 Box-level requirements on image items .9
7.2.2 Box-level requirements on image sequences and video . 12
7.3 Item level requirements on image items . 12
7.3.1 General . 12
7.3.2 Primary item . 12
7.3.3 MIAF thumbnail images . 12
7.3.4 MIAF master image items that are not the primary item . 13
7.3.5 MIAF auxiliary image items . 13
7.3.6 Item properties .14
7.3.7 Content light level property .16
7.3.8 Mastering display colour volume property .16
7.3.9 Transformations and derived items .16
7.3.10 Metadata .16
7.3.11 Derived images and derived image items .17
7.3.12 Image grouping .19
7.4 Track-level requirements on image sequences and video . 20
7.4.1 General . 20
7.4.2 Track reference types . 20
7.4.3 Video track-level requirements . 20
7.4.4 Video track sample entry boxes . 20
7.4.5 Audio track-level requirements .21
7.4.6 Auxiliary video track-level requirements .21
7.5 Association of image items and tracks .21
7.6 Metadata .21
8 Shared conditions and requirements .22
8.1 General . 22
8.2 Self-containment . 22
8.2.1 Image items . 22
8.2.2 Image sequences and video . 22
8.3 Single-layer . 22
8.4 Grid-limit . . 22
8.5 Single-track . 22
8.6 Edit-lists . 22
8.7 Matched-duration . 23
© ISO/IEC 2025 – All rights reserved
iii
8.8 HDR signalling . 23
9 Profile-independent image item and sequence coding .24
10 Brands and file extensions .24
10.1 General .24
10.2 Progressive application brand .24
10.3 Animation application brand . 25
10.4 Burst capture application brand . 26
10.5 Fragmented alpha video brand . 26
10.6 Common media fragmented brand. 26
Annex A (normative) MIAF profiles .27
Annex B (Informative) Reference software and conformance .32
Bibliography .34
© ISO/IEC 2025 – All rights reserved
iv
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).
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
database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held
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
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.
This second edition cancels and replaces the first edition (ISO/IEC 23000-22:2019), which has been
technically revised. It also incorporates the Amendments ISO/IEC 23000-22:2019/Amd 1:2021 and
ISO/IEC 23000-22:2019/Amd 2:2021.
The main changes are as follows:
— additional adjustments on chroma subsampling.
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 2025 – All rights reserved
v
Introduction
This document specifies a multimedia application format, the Multi-Image Application Format (MIAF), that
enables precise interoperability points for creation, reading, parsing, and decoding of images embedded in
the High Efficiency Image File (HEIF) format. This document (MIAF) fully conforms to the HEIF format and
only defines additional constraints to ensure higher interoperability.
ISO/IEC 23008-12 (HEIF) defines a file format for the inclusion of one or more images, possibly with one or
more sequences of images, with associated metadata and their relationship to each other. While the HEIF
specification defines the file format and general requirements for the included coding formats, it does not
define specific interoperability points by which capturing devices, editing applications, storage systems,
cloud and delivery networks, and playback devices and applications can interoperate with each other.
This document, by defining specific constraints on the HEIF format, limiting the supported encoding types
to a set of specific profiles and levels, requiring specific metadata formats, and defining a set of brands for
signalling such constraints, defines precise interoperability points which enable the industry to deploy
particular uses of the HEIF specification to improve interoperability.
This document defines the normative requirements for MIAF files as well as for MIAF readers and renderers.
© ISO/IEC 2025 – All rights reserved
vi
International Standard ISO/IEC 23000-22:2025(en)
Information technology — Multimedia application format
(MPEG-A) —
Part 22:
Multi-image application format (MIAF)
1 Scope
This document specifies the Multi-Image Application Format (MIAF), which contains coded images, groups
and sequences of images along with their metadata and the information about their relations to each other,
all embedded in the High Efficiency Image File (HEIF) format.
This document builds on ISO/IEC 23008-12 (HEIF) and specifies the following:
— a set of additional constraints on ISO/IEC 23008-12 (HEIF), to simplify its file format options;
— specific alpha plane formats;
— a set of specific profiles and levels for the supported coding formats;
— a set of specific metadata formats;
— a set of brands, including application brands indicating conformance with specific profiles;
— a set of rules for extending MIAF format to support additional coding formats, profiles, levels and
metadata.
This document also defines the normative behaviour for a MIAF reader and MIAF renderer.
This document (MIAF) is intentionally written to be extensible, and to allow for forward compatibility. The
format is also permissive of the presence of other data, such as coding formats, metadata, and derived images.
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 14496-3, Information technology — Coding of audio-visual objects — Part 3: Audio
Rec. ITU-T H.264 | ISO/IEC 14496-10, Information technology — Coding of audio-visual objects — Advanced
video coding
ISO/IEC 14496-12, Information technology — Coding of audio-visual objects — Part 12: ISO base media 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
Rec. ITU-T T.802 | ISO/IEC 15444-3, Information technology — JPEG 2000 image coding system — Part 3:
Motion JPEG 2000
ISO 16684-1, Graphic technology — Extensible metadata platform (XMP) — Part 1: Data model, serialization
and core properties
© ISO/IEC 2025 – All rights reserved
ISO/IEC 23000-19, Information technology — Multimedia application format (MPEG-A) — Part 19: Common
media application format (CMAF) for segmented media
ISO/IEC 23001-14, Information technology — MPEG systems technologies — Part 14: Partial file format
Rec. ITU-T H.265 | ISO/IEC 23008-2, Information technology — High efficiency coding and media delivery in
heterogeneous environments — High efficiency video coding
ISO/IEC 23008-12, Information technology — High efficiency coding and media delivery in heterogeneous
environments — Part 12: Image File Format
JEITA CP-3451, Exchangeable image file format for digital still cameras
3 Terms and definitions
For the purposes of this document, the terms and definitions given in Rec. ITU-T H.264 | ISO/IEC 14496-10,
ISO/IEC 14496-12, Rec. ITU-T H.265 | ISO/IEC 23008-2, ISO/IEC 23008-12 and the following 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
alpha plane
image specifying the transparency information of the master image
Note 1 to entry: When the resolution of an alpha plane differs from that of the master image, MIAF renderers are
expected to rescale the alpha plane to the resolution of the master image, but the rescaling operation is not specified
exactly and thus the exact behaviour of different MIAF renderer implementations can differ.
3.2
depth map
image that contains information relating to the distance of the surfaces of scene objects from a viewpoint
3.3
MIAF application brand
brand indicating that a MIAF file (3.5) conforms to additional requirements that apply to all MIAF profiles
(3.8) and that MIAF readers (3.9) and MIAF renderers (3.12) that implement these requirements may process
the MIAF file
3.4
MIAF auxiliary image item
image item that provides auxiliary visual information but is not normally independently rendered
Note 1 to entry: The requirements are in subclause 7.3.5.
3.5
MIAF file
file containing one or more image and/or image sequence and/or video tracks
Note 1 to entry: A MIAF file is constrained to conform to clause 7.
3.6
MIAF master image item
image item that may be rendered
3.7
MIAF image item
MIAF master image item (3.6), MIAF auxiliary image item (3.4) or MIAF thumbnail image item (3.10)
© ISO/IEC 2025 – All rights reserved
3.8
MIAF profile
set of restrictions on a MIAF file (3.5)
Note 1 to entry: These are typically restrictions on the media coding format/profile/level, content protection scheme,
or on quantitative measures. MIAF profiles enable interoperability between MIAF files and MIAF readers.
Note 2 to entry: A MIAF file may conform to multiple MIAF profiles. A MIAF reader or MIAF renderer may be capable of
processing one or more MIAF profiles.
3.9
MIAF reader
entity that reads and parses MIAF files (3.5), identifies the type of image coding and metadata, and decodes
the coded streams for the coding types/profiles/levels that it supports
3.10
MIAF thumbnail image item
image item that is referenced using the thumbnail reference type
Note 1 to entry: The requirements for a MIAF thumbnail image item are specified in subclause 7.3.3.
3.11
MIAF player
entity including a MIAF reader (3.9) and a MIAF renderer (3.12)
3.12
MIAF renderer
entity that renders the output of MIAF reader (3.9) into a visual context (3.15), taking into account associated
metadata (e.g. colour information) and auxiliary image data (e.g. alpha planes)
3.13
primary image
image identified as the primary item (3.14) in the file-level MetaBox
3.14
primary item
item as identified by the PrimaryItemBox in the file-level MetaBox
3.15
visual context
visual rendering surface such as a screen buffer, which may already contain visual material, and onto which
an image can be rendered
3.16
CICP colour information
metadata provided by a colour information box or property with colour_type equal to 'nclx'
3.17
ICC colour information
metadata provided by a colour information box or property with colour_type equal to 'prof' or 'rICC'
© ISO/IEC 2025 – All rights reserved
4 Abbreviated terms
AVC Advanced Video Coding (as specified by Rec. ITU-T H.264|ISO/IEC 14496-10)
CICP Coding-independent Code Points (as specified by ISO/IEC 23091-2)
HEIF High Efficiency Image File format (as specified by ISO/IEC 23008-12)
HEVC High Efficiency Video Coding (as specified by Rec. ITU-T H.265|ISO/IEC 23008-2)
ICC International Color Consortium
MIAF Multi Image Application Format (as specified by this document)
5 Document organization and conventions
Clause 6 specifies general concepts and processing of MIAF files.
Clause 7 specifies general requirements that apply to all MIAF profiles. These requirements are categorized
into two types:
— requirements at the file format structure level, and requirements at the 'abstraction layer' that the file
format structures create; and
— requirements for both still images, image sequences and video.
Clause 8 specifies constraints which are shared by one or more MIAF profiles.
Clause 9 specifies the coding format(s) that shall be supported in any player, independent of any MIAF profile.
Clause 10 specifies the MIAF application brands that indicate conformance to the normative requirements
of this document, common to all MIAF profiles (as documented in the clauses preceding the annexes), and
the applicable file extensions.
Annex A specifies the MIAF profiles, each of which imposes a set of specific restrictions which shall be
followed for enabling interoperability between MIAF files and MIAF readers.
Annex B provides detailed information on the publicly available conformance and reference software with a
description of the tool used for conformance evaluation.
This document derives variables that are named by a mixture of lower case and upper case letters and
without any underscore characters. Variables starting with an upper case letter are derived for the current
syntax structure and all depending syntax structures. Variables starting with an upper case letter may
be used in the specification for dependent syntax structures without mentioning the originating syntax
structure of the variable. Variables starting with a lower case letter are only used within the clause in which
they are derived.
6 MIAF concepts and processing of MIAF files
6.1 General
This clause describes the overall encoding, packaging, parsing and decoding architecture as well as the data
structure (concepts of image, image sequence, video, metadata, etc.).
This document places requirements on
— the format of files;
— the action of a process that reads and parses a file, and produces output images (a "reader");
— the action of a process that renders the output images (a "renderer").
© ISO/IEC 2025 – All rights reserved
Figure 1 illustrates a possible processing model to handle MIAF files. A MIAF reader gets a MIAF file as input.
In addition, the caller process or application provides inputs on how the file is intended to be processed. The
MIAF reader produces output images that are provided to the MIAF renderer for displaying. The rendering
takes place on a visual context, such as a screen buffer, and is controlled by the caller process or application.
Figure 1 — Processing of a MIAF file.
6.2 MIAF data object model
The data object model consists of the boxes at the file format layer, and the two abstraction layers that those
boxes create:
— image items, with their properties, and relationships (expressed by item references);
— image sequences and/or video, with the sample entry setup information, and their relationships
(expressed by track references).
These two abstraction layer models can be linked by references and entity groups.
Image items are suitable when neither timing nor coding dependency is required. If either timing is required
or the coding scheme takes advantage of inter-picture prediction, an image sequence track or a video track
is used. A key difference between image sequence tracks and video tracks is that, in image sequence tracks,
the timing is advisory. Consequently, it is suggested that MIAF files contain image sequence tracks when
timing is not meaningful or essential for playback — for example, images captured with exposure or focal
bracketing.
6.3 MIAF image items
A MIAF image item is independently decodable and represented by an image item that conforms
a) to the box-level requirements for image items in subclause 7.2.1 and
b) to the requirements for image items in subclause 7.3 and
c) to the requirements of a defined MIAF profile, if it exists, and for which a brand should appear in the
FileTypeBox.
6.4 MIAF thumbnail image items
A MIAF thumbnail image item is a MIAF image item that
a) is referenced as a thumbnail image from a MIAF master image item;
b) has its image data stored in the same file as the MIAF master image item for which it is a thumbnail.
6.5 MIAF auxiliary image item
A MIAF auxiliary image item is a MIAF image item that
a) conforms also to the requirements for auxiliary image items in subclause 7.3.5;
© ISO/IEC 2025 – All rights reserved
6.6 MIAF reader processing model
A MIAF reader is an entity capable of:
a) concluding which image item(s) or track(s) of a MIAF-conforming file are to be output based on given
input parameters;
b) decoding image items(s) or track(s) to be output;
c) generating the output pictures from the decoded pictures (e.g. by applying transformative image
properties); and
d) outputting the output pictures and file metadata associated with the output pictures.
Inputs to a MIAF reader are:
— a file compliant to this document;
— optionally one of the following:
— item_ID of the item to be output (psItemId),
— track_ID of the track to be output (psTrackId),
— a selection between a static image (psImagePreferredFlag equal to 1) or track (psImagePreferredFlag
equal to 0) to be output,
NOTE 1 When neither psItemId nor psTrackId is provided as input, a default image item or track is
selected as specified in this clause.
— optionally constraints, such as the maximum width and height of an image item or track;
— optionally one or more of the following roles of the image or track to be output:
— master (default),
— thumbnail,
— auxiliary, which may be further classified by the type.
NOTE 2 More than one role can be provided as input for example to instruct a MIAF reader to return
both an image item and its alpha plane (when present).
Outputs of a MIAF reader are:
— the output image(s) of the track(s) or item(s) that was (were) requested as input or selected by the MIAF
reader as specified below, not including any non-output samples as defined in ISO/IEC 14496-12;
— in the case that any tracks are present, the composition times for each output sample, with any associated
edit list;
— the metadata associated with the output image(s), including the content of the colour information 'colr'
descriptive item property or ColourInformationBox box(es).
NOTE 3 All colour properties are expected to be parsed by MIAF readers, including all colour types (on-screen
i.e. colour_type equal to 'nclx', constrained and unconstrained ICC profiles), and passed as metadata to the
MIAF renderer.
NOTE 4 When a MIAF reader is requested to provide auxiliary images as output, the output image(s) of the
MIAF reader include output images of auxiliary image item(s) or decoded samples of auxiliary track(s) of any
type, when no input of auxiliary picture type is given to the MIAF reader, or of the type matching that given as
input to the MIAF reader.
© ISO/IEC 2025 – All rights reserved
A track_ID or item_ID value seedId is derived using the following ordered steps:
— If neither psItemId nor psTrackId is provided as input, the following applies:
— If there is an alternate group including the primary item of the file, the following applies:
— If psImagePreferredFlag is provided as input and is equal to 0, the tracks in the alternate group
are examined in the order they are listed in the alternate group and seedId is set equal to the
track_ID value of the first track that the MIAF reader is able to decode and that fulfils the
constraints provided as input, if any.
— Otherwise, if psImagePreferredFlag is provided as input and is equal to 1, the items in the
alternate group are examined in the order they are listed in the alternate group and seedId is
set equal to the item_ID value of the first item that the MIAF reader is able to decode and that
fulfils the constraints provided as input, if any.
— Otherwise (psImagePreferredFlag is not provided as input), the tracks and items in the alternate
group are examined in the order they are listed in the alternate group and seedId is set equal to
the track_ID or item_ID value of the first track or item that the MIAF reader is able to decode
and that fulfils the constraints provided as input, if any.
NOTE 5 The selection of an entity from an alternate group can be implemented in a MIAF reader as
follows. At least the initial part of the file is retrieved for inspection — enough to cover the FileTypeBox,
and MetaBox and possibly the MovieBox (if any). The MetaBox is then inspected to find the identification of
the primary item, and any of its alternatives indicated by an alternate group. If there are alternatives, the
MIAF reader selects the first such entity listed in the alternate group that the MIAF reader can support —
with regards to compatible coding format, existence of protection, and so on, and that fulfils the constraints
provided as input, if any.
— Otherwise, the following applies:
— If psImagePreferredFlag is not provided as input, or is equal to 1, seedId is set equal to the item_
ID value of the primary item.
— Otherwise, seedId is set equal to the track_ID value of any track conforming to this document
and fulfils the constraints provided as input, if any.
— Otherwise, if psItemId is provided as input, seedId is set equal to psItemId.
— Otherwise, seedId is set equal to psTrackId.
A list of track_ID or item_ID values to be decoded, selectedIds, is derived as follows:
— If seedId represents a track_ID and one or more roles are provided as input, selectedIds is a list of track_
ID values such that both of the following are true for each list element selectedIds[listIdx]:
— selectedIdsx[listIdx] is equal to seedId or the track_ID value of any auxiliary and thumbnail tracks
associated with the track having track_ID equal to seedId;
— the track with the track_ID value equal to selectedIds[listIdx] has a role that is given as input.
— Otherwise, if seedId represents an item_ID and one or more roles are provided as input, selectedIds is a
list of item_ID values such that both of the following are true for each list element selectedIds[listIdx]:
— selectedIds[listIdx] is equal to seedId or the item_ID value of any auxiliary and thumbnail items
associated with the item having item_ID equal to seedId;
— the item with the item_ID value equal to selectedIds[listIdx] has a role that is given as input.
— Otherwise, selectedIds is either empty or a list that has one and only one list element that is set equal
to seedId.
NOTE 6 selectedIds can contain multiple items, such as a master image item and its thumbnail image item, when
more than one role is given as an input to a MIAF reader.
© ISO/IEC 2025 – All rights reserved
A MIAF reader concludes an error when any of the following occurs:
— selectedIds contains no track_ID or item_ID values;
— one or more roles are provided as input and selectedIds contains a track_ID or item_ID value of a track
or item that has a role other than those provided as input.
NOTE 7 A MIAF reader retrieves enough of the data-portion of the file (identified by offsets and sizes in the data
already retrieved) to enable the decoding and reconstruction of the output image(s) or image sequence(s) or video(s),
represented by the image items or tracks identified by selectedIds.
A MIAF reader decodes each track or item identified by the values in selectedIds and provides as output
the output images of the decoded image items or the decoded samples, including the application of
transformations.
1. Derive output image(s) from the image item(s) to be output, if any, as specified in ISO/IEC 23008-12.
2. Decode image sequence or video track(s) to be output, if any, and apply matrix of TrackHeaderBox and
CleanApertureBox to the decoded pictures to generate pictures to be output.
For each output image, the MIAF reader returns metadata, such as colour information.
NOTE 8 Decoding of an image item can involve image derivation, or the application of transformative properties
applied in sequence. MIAF readers are expected to only use CICP colour information during decoding, derivation,
transformation or colour conversion, and to ignore ICC colour information.
6.7 MIAF renderer processing model
Inputs to a MIAF renderer are:
— the output image(s) of the item(s) or the sample(s) of the track(s) that were provided as output by the
MIAF reader;
— in the case that any tracks are present, the composition times of the output samples, with their associated
edit lists;
— the metadata associated with the output image(s), including the content of the colour information 'colr'
descriptive item property or ColourInformationBox box(es).
— a visual context, such as a bitmap representing a displaying window prior to rendering the output
image(s).
Outputs of a MIAF renderer are:
— A new visual context subsequent to rendering the output image(s) into the provided visual context.
NOTE 1 When the output image(s) provided as output by the MIAF reader include(s) auxiliary image(s), this (these)
auxiliary image(s) is (are) also provided as input to the MIAF renderer.
MIAF profiles or MIAF application brands may specify the operation of the MIAF renderer. When MIAF
profiles or MIAF application brands do not specify the operation of the MIAF renderer and no other
information of the MIAF renderer operation is available, the MIAF renderer should operate as follows.
If an output image given as input to the MIAF renderer resulted from an image item, the following processing
steps are applied once to produce the updated visual context. Otherwise, if output image(s) given as input
to the MIAF renderer resulted from a video track, the following processing steps are applied multiple times
using the timing provided by the edit list, if any, or composition times, otherwise.
NOTE 2 Colour properties and other descriptive properties are expected to be used to enable display matching.
MIAF renderers are expected to use the various colour information from the MIAF reader in the following order of
preference (from most preferred to least preferred): ICC profile information, if available; CICP colour information, if
not set to unknown; application-provided colour information, if available; default CICP colour information, as defined
in 7.3.6.4.
© ISO/IEC 2025 – All rights reserved
NOTE 3 No default rendering for an image sequence track is specified. A proper rendering of an image sequence
track depends on the use case or capturing scenario for the image sequence track.
If both a master image and an associated alpha plane are provided as inputs to the processing model, the
following applies:
— When the width or the height of the alpha plane differs from the width or the height of the master image,
respectively, the alpha plane is resized to have the same width and height as those of the master image.
— If the master image is not pre-multiplied, the visual context is updated by performing the following
operation for each co-located pixel of the master image and the visual context:
v = m × α + v × (1 − α)
u i
— Otherwise (the master image is pre-multiplied), the visual context is updated by performing the following
operation for each co-located pixel of the master image and the visual context:
v = m + v × (1 − α)
u i
where
v is a pixel value in the updated visual context;
u
m is a pixel value in the master image;
α is an alpha plane value, scaled into the range of 0 (fully transparent) to 1 (fully opaque), inclusive;
v is a pixel value in the visual context given as input to the process.
i
Otherwise (no alpha plane with a master image is provided as input to the processing model), the master
image is opaquely overlaid on the visual context.
7 MIAF file general requirements
7.1 General
A MIAF file shall conform to the requirements specified by ISO/IEC 23008-12 (which in turn references
requirements in ISO/IEC 14496-12).
A MIAF reader shall process all normative parts of a MIAF file.
NOTE A MIAF file can contain data additional to that defined by this document. A MIAF reader is expected to
ignore and/or skip the data it does not understand, and continue processing the received file.
7.2 Box-level requirements
7.2.1 Box-level requirements on image items
7.2.1.1 General
A summary of the boxes in MIAF that support image items is in Table 1. Indentation is used to represent
which boxes are enclosed in others. The names are the formal syntax names of the boxes. The clause numbers
indicate subclauses of this document that provide requirements and restrictions on those boxes.
© ISO/IEC 2025 – All rights reserved
Table 1 — Box overview and nesting for image items
Box overview and nesting for image items
file type and compat-
FileTypeBox
7.2.1.2
ibility
BoxFileIndexBox
7.2.1.3 file index
MetaBox
7.2.1.4 metadata
handler, declares the
HandlerBox
7.2.1.5 metadata (handler)
type
data information
DataInformationBox
7.2.1.6
box, container
data reference box,
DataReferenceBox 7.2.1.6 declares source(s) of
metadata items
ItemLocationBox
7.2.1.7 item location
ItemProtectionBox
7.2.1.8 item protection
ItemInfoBox
7.2.1.9 item information
primary item refer-
PrimaryItemBox
7.2.1.10
ence
ItemPropertiesBox 7.2.1.11 item properties
ItemReferenceBox 7.2.1.12 item reference
ItemDataBox
7.2.1.13 item data
GroupsListBox
7.3.12 entity grouping
EntityToGroupBox
7.3.12
MediaDataBox
7.2.1.13 media data container
Boxes documented in ISO/IEC 23008-12, ISO/IEC 14496-12 or ISO/IEC 23001-14 are shown in Table 1. Other
boxes may be present in the file but they shall not affect the processing of any images that are required or
conditionally required by this document.
Any MIAF file has the following constraints:
— The file shall conform to the constraints of the 'mif1' brand specified in ISO/IEC 23008-12;
— When the file contains an image sequence track, the file shall conform to the constraints of the 'msf1'
brand specified in ISO/IEC 23008-12.
— When the file contains a video track, the file shall conform to the constraints of any brand specified in
ISO/IEC 14496-12.
— The file-level MetaBox shall always be present (see 7.2.1.4).
— The HandlerBox shall
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