ISO/IEC 23008-12:2017/Amd 1:2020

Information technology - High efficiency coding and media delivery in heterogeneous environments - Part 12: Image File Format - Amendment 1: Support for predictive image coding, bursts, bracketing and other improvements

Technologies de l'information — Codage à haute efficacité et livraison des medias dans des environnements hétérogènes — Partie 12: Format de fichier d'image — Amendement 1: Support pour le codage prédictif des images, les rafales, le bracketing et autres améliorations

General Information

• Status: Withdrawn
• Publication Date: 22-Nov-2020
• 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: 9599 - Withdrawal of International Standard
• Start Date: 29-Sep-2022
• Completion Date: 30-Oct-2025

Relations

• Amends: ISO/IEC 23008-12:2017 - Information technology - High efficiency coding and media delivery in heterogeneous environments - Part 12: Image File Format
• Effective Date: 01-Jan-2022
• Revised: ISO/IEC 23008-12:2022 - Information technology - High efficiency coding and media delivery in heterogeneous environments - Part 12: Image File Format
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 23008-12
First edition
2017-12
AMENDMENT 1
2020-11
Information technology — High
efficiency coding and media delivery
in heterogeneous environments —
Part 12:
Image File Format
AMENDMENT 1: Support for predictive
image coding, bursts, bracketing and
other improvements
Technologies de l'information — Codage à haute efficacité et livraison
des medias dans des environnements hétérogènes —
Partie 12: Format de fichier d'image
AMENDEMENT 1: Support pour le codage prédictif des images, les
rafales, le bracketing et autres améliorations
Reference number
ISO/IEC 23008-12:2017/Amd.1:2020(E)
©
ISO/IEC 2020
ISO/IEC 23008-12:2017/Amd.1:2020(E)

© ISO/IEC 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved

ISO/IEC 23008-12:2017/Amd.1:2020(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
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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.
A list of all parts in the ISO/IEC 23008 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 iii

ISO/IEC 23008-12:2017/Amd.1:2020(E)
Information technology — High efficiency coding and
media delivery in heterogeneous environments —
Part 12:
Image File Format
AMENDMENT 1: Support for predictive image coding, bursts,
bracketing and other improvements

Clause 3
Add the following terms and definitions at the end of 3.1:
3.1.40
predictively coded image item
image item (3.1.17) that has a decoding dependency to one or more other coded image items (3.1.5)
3.1.41
unique ID
identifier for either an item, an entity group or a track that fulfils the requirements of the 'unif' brand
Note 1 to entry: Requirements on the 'unif' brand are specified in ISO/IEC 14496-12.
3.1.42
visual context
visual rendering surface such as a screen buffer, which may already contain visual material, and onto
which an image (3.1.15) can be rendered

Clause 4, item a)
Replace the text in item a) with the following:
a) the storage of a single coded image or a collection of coded images, possibly with derived images;
coded images are normally independently coded except when the 'pred' brand is signalled. In
such latter case, coded images may be independently coded or may have been coded with inter
prediction;
Clause 4, third paragraph:
Replace the third paragraph with the following:
In general, the single image support is used for simpler cases, particularly when neither timing nor
coding dependency is required. If advisory timing or other tools from the ISO base media file format
available for tracks are needed (e.g. sample grouping), then the second approach is needed.
© ISO/IEC 2020 – All rights reserved 1

ISO/IEC 23008-12:2017/Amd.1:2020(E)

6.4
Add the following new subclause after subclause 6.4.8:
6.4.9  Predictively coded image items
Predictively coded image items have a decoding dependency to one or more other coded image items.
An example for such an image item could be a P frame stored as an image item in a burst entity group
that has IPPP… structure, with the P frames dependent only on the preceding I frames.
Capability to have predictively coded image items has certain benefits especially in content re-editing
and cover image selection:
— Image sequences can be converted to image items with no transcoding.
— Any sample of an image sequence track can be selected as a cover image. The cover image does not
need to be intra-coded.
— Devices that do not have a video or image encoder are capable of updating the cover image of a file
containing an image sequence track.
— Storage efficiency is further achieved by re-using the predictively coded picture rather than re-
encoding it as I frame and storing as an additional image item. Moreover, image quality degradation
is also avoided.
— Re-encoding might not be allowed or preferred by the copyright owner. Predictively coded image
items avoid the need of re-encoding of any image from an image sequence track.
Predictively coded image items are linked to the coded image items they directly and indirectly depend
on by item references of type 'pred'. The list of referenced items in item references of type 'pred'
shall indicate the decoding order. When concatenated, the encoded media data of items with item_ID
equal to to_item_ID for all values of j from 0 to reference_count − 1, inclusive, in increasing order of
j, followed by the item with item_ID equal to from_item_ID shall form a bitstream that conforms to the
decoder configuration item property of the predictively coded image item.
In order to decode the predictively coded image item, there shall be no other decoding dependencies
other than the image items referenced by item references of type 'pred'.
The predictively coded image item shall be associated with exactly one RequiredReferenceTypesProperty
containing one reference type with the value 'pred'.

6.5.1
Add the following paragraphs at the end of the subclause 6.5.1, after the NOTE:
When unique IDs are used, an item_ID value in the ItemPropertyAssociationBox is resolved to an item
identifier whenever the embedding MetaBox contains an item with such identifier, and is resolved to an
entity group identifier otherwise.
Properties may be associated with an entity group, but only when explicitly stated in their specification.
In such case, properties apply to the entity group as a whole, and not individually to each entity within
the group.
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6.5
Add the following new subclauses after subclause 6.5.12:
6.5.13  Image scaling
6.5.13.1  Definition
'iscl'
Box type:
Property type: Transformative item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The image scaling 'iscl' transformative item property scales an input image.
The input image is the output of the previous transformative item property, if any, or the reconstructed
image of the associated image item.
The width and height of the input image (call those input_width and input_height) are resized to a
target width and height, in pixels, respectively equal to ceil( (input_width * target_width_numerator)
/ target_width_denominator) and ceil((input_height * target_height_numerator) / target_height_
denominator), where ceil() is the ceiling function. The scaling of the input image applies to both width
and height separately. The fraction may or may not be in reduced terms.
NOTE 1 Formulas above use a floating-point division, not an integer division.
NOTE 2 When the input image is the reconstructed image of the associated image item, input_
width and input_height, respectively, are equal to image_width and image_height declared in the
ImageSpatialExtentsProperty associated with this image item. Otherwise, input_width and input_height
are equal to the width and height of the output of the previous transformative item property.
6.5.13.2  Syntax
aligned(8) class ImageScaling
extends ItemFullProperty('iscl', version = 0, flags = 0) {
unsigned int (16) target_width_numerator;
unsigned int (16) target_width_denominator;
unsigned int (16) target_height_numerator;
unsigned int (16) target_height_denominator;
}
6.5.13.3  Semantics
target_width_numerator specifies the numerator of the scaling ratio for the resized image in the
horizontal dimension. The value 0 shall not be used.
target_width_denominator specifies the denominator of the scaling ratio for the resized image in the
horizontal dimension. The value 0 shall not be used.
target_height_numerator specifies the numerator of the scaling ratio for the resized image in the
vertical dimension. The value 0 shall not be used.
target_height_denominator specifies the denominator of the scaling ratio for the resized image in the
vertical dimension. The value 0 shall not be used.
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6.5.14  Content light level
6.5.14.1  Definition
'clli'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The content light level item property provides information about the light level in the content.
6.5.14.2  Syntax
The content light level 'clli' descriptive item property has the same syntax as the ContentLightLevelBox
as defined in ISO/IEC 14496-12.
6.5.14.3  Semantics
The semantics of the syntax elements within the content light level 'clli' item property are the same
as those specified for the syntax elements of ContentLightLevelBox as defined in ISO/IEC 14496-12.
6.5.15  Mastering display colour volume
6.5.15.1  Definition
'mdcv'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
This property provides information about the colour primaries, white point, and mastering luminance
in the content.
6.5.15.2  Syntax
This property has the same syntax as the MasteringDisplayColourVolumeBox as defined in
ISO/IEC 14496-12.
6.5.15.3  Semantics
The semantics of the syntax elements within this property are the same as those specified for the
syntax elements of MasteringDisplayColourVolumeBox as defined in ISO/IEC 14496-12.
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6.5.16  Content colour volume
6.5.16.1  Definition
'cclv'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
This property describes the colour volume characteristics of the associated pictures.
6.5.16.2  Syntax
This property has the same syntax as the ContentColourVolumeBox as defined in ISO/IEC 14496-12.
6.5.16.3  Semantics
The semantics of the syntax elements within this property are the same as those specified for the
syntax elements of ContentColourVolumeBox as defined in ISO/IEC 14496-12.
6.5.17  Required reference types
6.5.17.1  Definition
'rref'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): Yes, for a predictively coded image item. No, otherwise.
Quantity (per item): At most one
The RequiredReferenceTypesProperty descriptive item property lists the item reference types that a
reader shall understand and process to decode the associated image item. The respective essential
flag shall be equal to 1 in ItemPropertyAssociationBox.
NOTE In the absence of this property, required reference types are not explicitly listed, but can still exist.
6.5.17.2  Syntax
aligned(8) class RequiredReferenceTypesProperty
extends ItemFullProperty('rref', version = 0, flags = 0){
unsigned int(8) reference_type_count;
for (i=0; i< reference_type_count; i++) {
unsigned int(32) reference_type[i];
}
}
6.5.17.3  Semantics
reference_type_count indicates the number of reference types that are required to understand and
process to decode the associated image item.
reference_type[i] indicates a reference type that is required to understand and process to decode the
associated image item.
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ISO/IEC 23008-12:2017/Amd.1:2020(E)

6.5.18  Creation time information
6.5.18.1  Definition
'crtt'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per associated item_ID): No
Quantity (per associated item_ID): At most one
The CreationTimeProperty documents the creation time of the associated item or group of entities.
6.5.18.2  Syntax
aligned(8) class CreationTimeProperty
extends ItemFullProperty('crtt', version = 0, flags = 0) {
unsigned int(64) creation_time;
}
6.5.18.3  Semantics
creation_time is an integer that declares the creation time of the item or group of entities (in
microseconds since midnight, Jan. 1, 1904, in UTC time).
6.5.19  Modification time information
6.5.19.1  Definition
'mdft'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per associated item_ID): No
Quantity (per associated item_ID): At most one
The ModificationTimeProperty documents the last modification time of the associated item or group
of entities.
6.5.19.2  Syntax
aligned(8) class ModificationTimeProperty
extends ItemFullProperty('mdft', version = 0, flags = 0) {
unsigned int(64) modification_time;
}
6.5.19.3  Semantics
modification_time is an integer that declares the most recent time the item or group of entities was
modified (in microseconds since midnight, Jan. 1, 1904, in UTC time).
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6.5.20  User description
6.5.20.1 Definition
'udes'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per associated item_ID): No
Quantity (per associated item_ID): Zero or more
The UserDescriptionProperty permits the association of item(s) or entity group(s) with a user-
defined name, description and tags; there may be multiple such properties, which shall have different
language codes.
When several instances of UserDescriptionProperty are associated with the same item or entity group,
they represent alternatives possibly expressed in different languages and a reader should choose the
most appropriate. At most one UserDescriptionProperty with the same alt_lang value should apply to
the same item or entity group.
6.5.20.2  Syntax
aligned(8) class UserDescriptionProperty
extends ItemFullProperty('udes', version = 0, flags = 0){
utf8string lang;
utf8string name;
utf8string description;
utf8string tags;
}
6.5.20.3  Semantics
lang is a character string containing an IETF RFC 5646 compliant language tag string, such as "en-
US", "fr-FR", or "zh-CN“, representing the language of the text contained in name, description and tags.
When lang is empty, the language is unknown/undefined.
name is a null-terminated UTF-8 character string containing human readable name for the item or
group of entities. If not present (an empty string is supplied) no name is provided.
description is a null-terminated UTF-8 character string containing human readable description of the
item or group of entities. If not present (an empty string is supplied) no description is provided.
tags is a null-terminated UTF-8 character string containing comma-separated user-defined tags
related to the item(s). If not present (an empty string is supplied) no tags is provided.
6.5.21  Accessibility text
6.5.21.1  Definition
'altt'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per an item): No
Quantity (per an item): Zero or more
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The AccessibilityTextProperty contains a string suitable to be used as an alternate text for an image
if the image cannot be displayed, similarly to alt text in HTML. The language used by the alternate text
is represented by a language tag string compliant with IETF RFC 5646.
When several instances of AccessibilityTextProperty are associated with the same item, they
represent alternatives possibly expressed in different languages and a reader should choose the most
appropriate. At most one AccessibilityTextProperty with the same alt_lang value should apply to
the same item.
6.5.21.2  Syntax
aligned(8) class AccessibilityTextProperty
extends ItemFullProperty('altt', version = 0, flags = 0) {
utf8string alt_text;
utf8string alt_lang;
}
6.5.21.3  Semantics
alt_text is a character string suitable to be used as an alternate text for an image if the image cannot
be displayed, similarly to alt text in HTML.
alt_lang is a character string containing an IETF RFC 5646 compliant language tag string, such as "en-
US", "fr-FR", or "zh-CN“, representing the language of the text contained in alt_text. When alt_lang is
empty, the language is unknown/undefined.
6.5.22  Auto Exposure Information
6.5.22.1  Definition
'aebr'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The auto exposure descriptive item property defines the exposure variation of the associated image
item relatively to the camera settings.
It is used to specify the properties of an image item included in an 'aebr' entity group as specified in
subclause 6.8.6.
6.5.22.2  Syntax
aligned(8) class AutoExposureProperty
extends ItemFullProperty('aebr', version = 0, flags = 0) {
int(8) exposure_step;
int(8) exposure_numerator;
}
6.5.22.3  Semantics
exposure_step is an integer value that specifies the increment steps used during the exposure
bracketing. When equals to 1, a full stop increment is used, when equals to 2, a half stop increment is
used, when equals to 3, a third stop increment is used, and when equals to 4, a quarter stop increment is
used. Other values are reserved.
exposure_numerator is an integer value specifying the exposure numerator used to compute the
exposure value stop of the item.
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The exposure value variation of the associated image item compared to the camera settings is expressed
as a number of stops, and is computed as exposure_numerator/exposure_step.
6.5.23  White balance information
6.5.23.1  Definition
'wbbr'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The white balance descriptive item property defines the white balance compensation on blue/amber
bias and/or magenta/green bias applied to the associated image item relatively to the camera settings.
It is used to specify the properties of an image item included in a 'wbbr' entity group as specified in
subclause 6.8.6.
6.5.23.2  Syntax
aligned(8) class WhiteBalanceProperty
extends ItemFullProperty('wbbr', version = 0, flags = 0) {
unsigned int(16) blue_amber;
int(8) green_magenta;
}
6.5.23.3  Semantics
blue_amber is an unsigned integer indicating the colour temperature component of the white balance
in Kelvin.
green_magenta is a signed integer indicating the colour deviation component of white balance in unit of
1/100 Duv (distance to the blackbody locus).
NOTE A Duv of 0 indicates a light source that is neutral. A negative Duv indicates a magenta colour shift,
while a positive Duv indicates a green colour shift.
6.5.24  Focus information
6.5.24.1  Definition
'fobr'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The focus descriptive item property defines the focus variation of the associated image item relatively
to the camera settings.
It is used to specify the properties of an image item included in an 'fobr' entity group as specified in
subclause 6.8.6.
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6.5.24.2  Syntax
aligned(8) class FocusProperty
extends ItemFullProperty('fobr', version = 0, flags = 0) {
unsigned int(16) focus_distance_numerator;
unsigned int(16) focus_distance_denominator;
}
6.5.24.3  Semantics
The focus distance is expressed in meter as the ratio of focus_distance_numerator and focus_distance_
denominator. Focus at infinity is expressed as division by zero, i.e. focus_distance_denominator is
equal to 0 and focus_distance_numerator should be equal to 0.
6.5.25  Flash exposure information
6.5.25.1  Definition
'afbr'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The flash exposure descriptive item property defines the flash exposure variation of the associated
image item relatively to the camera settings.
It is used to specify the properties of an image item included in an 'afbr' entity group as specified in
subclause 6.8.6.
6.5.25.2  Syntax
aligned(8) class FlashExposureProperty
extends ItemFullProperty('afbr', version = 0, flags = 0) {
int(8) flash_exposure_numerator;
int(8) flash_exposure_denominator;
}
6.5.25.3  Semantics
flash_exposure_numerator and flash_exposure_denominator are integers representing the flash
exposure value of the sample expressed in a number of f-stops as the ratio of flash_exposure_numerator
and flash_exposure_denominator.
6.5.26  Depth of field information
6.5.26.1  Definition
'dobr'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one
The depth of field descriptive item property defines the depth of field variation of the associated image
item relatively to the camera settings. It is expressed as an aperture change.
It is used to specify the properties of an image item included in a 'dobr' entity group as specified in
subclause 6.8.6.
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6.5.26.2  Syntax
aligned(8) class DepthOfFieldProperty
extends ItemFullProperty('dobr', version = 0, flags = 0) {
int(8) f_stop_numerator;
int(8) f_stop_denominator;
}
6.5.26.3  Semantics
The depth of field variation is expressed as an aperture change in a number of stops, and is computed
as f_stop_numerator/f_stop_denominator.
6.5.27  Panorama information
6.5.27.1  Definition
'pano'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per associated item_ID): No
Quantity (per associated item_ID): At most one
The panorama descriptive item property defines the characteristics associated with a panorama
defined by a 'pano' entity group.
This item property should only be associated with an entity group with grouping_type equal to 'pano'.
6.5.27.2  Syntax
aligned(8) class PanoramaProperty
extends ItemFullProperty('pano', version = 0, flags = 0) {
unsigned int(8) panorama_direction;
if (panorama_direction >= 4 && panorama_direction <= 5) { // grid
unsigned int(8) rows_minus_one;
unsigned int(8) columns_minus_one;
}
}
6.5.27.3  Semantics
panorama_direction is an unsigned integer signalling the type of panorama used and the scanning
order of input images in the panorama:
— 0: left-to-right horizontal panorama
— 1: right-to-left horizontal panorama
— 2: bottom-to-top vertical panorama
— 3: top-to-bottom vertical panorama
— 4: grid panorama in raster scan order, i.e. rows and columns are organised from left-to-right and
top-to-bottom starting from the top-left corner.
— 5: grid panorama in continuous order, i.e. starting from the top-left corner, the first row is organized
from left-to-right, then the second row is organised from right-to-left, the third row is organized
from left-to-right and so on.
other values are undefined.
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rows_minus_one is an unsigned integer that specifies the number of rows in the grid minus one.
columns_minus_one is an unsigned integer that specifies the number of columns in the grid minus one.

6.6.2.3
Replace the text in NOTE 1 with the following:
NOTE 1 If the desired input images are not of a consistent size, then derived image items that scale or crop
them, as needed to make them consistent, can be used; other specifications can, however, restrict whether
derived image items are permissible as input to the image grid derived image item. This document specifies
cropping in 6.5.8 and scaling in subclause 6.5.13.

6.8
Rename the heading of subclause 6.8 as “Entity and sample groups”.
Move the current subclause 6.8 “Relating an untimed item to a timed sequence" and all of its subclauses
to subclause 6.8.1. Add the following new subclause 6.8.2 at the end of the subclause:
6.8.2  Burst images
6.8.2.1  Overview
Burst images are a series of rapid succession images. Burst images can contain any number of images
and may benefit fully from the image sensor resolution or image processing pipeline, hence providing
access to high-resolution original versions of individual images of a burst capture.
An image burst may be stored as an image sequence track or a set of image items. The latter enables
flexible and advanced burst image storage and retrieval use cases such as storage of individual burst
images as derived image items.
6.8.2.2  'brst' entity group
The burst image entity group ('brst') indicates a set of images that form a temporal burst image
set. The entity_id values of the image items in a 'brst' entity group shall be listed in a temporally
increasing order.
When an image sequence track is included in a 'brst' entity group, there shall be only one entity_id
present in the 'brst' entity group. An image sequence track may be included in a 'brst' entity group
to indicate that it contains a burst-captured image sequence as opposed to other types of multi-image
captures, such as focal or exposure stacks.
There may be multiple 'brst' entity groupings in the same file with different group_id values.
6.8.3  'tsyn' entity group
A time-synchronized capture entity group ('tsyn') contains entities that were synchronously captured.
A single 'tsyn' entity group shall include entity_id values that either resolve to image items or to
image sequence tracks, but not a mixture of both. A 'tsyn' entity group including image items indicates
that the image items were simultaneously captured spanning the same time. A 'tsyn' entity group
including image sequence tracks indicates that all tracks in the group, if played using the timing in the
file, are in sync.
Tracks included in the same 'tsyn' entity group shall have the same duration.
There may be multiple 'tsyn' entity groupings in the same file with different group_id values.
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6.8.4 'iaug' entity group
An 'iaug' entity group associates an image item with an audio track. When displaying an image item
mapped to an 'iaug' entity group, a reader should also play the related audio track provided that audio
playback is enabled e.g. based on user preferences.
The number of entities in an 'iaug' entity group shall be exactly 2, one of the entity_id values shall
indicate an image item, and the other entity_id value shall indicate an audio track. The number of
'iaug' entity groups including a particular item_ID value shall not be greater than 1.
If the file contains alternative audio tracks to be played with an image item, the audio tracks should
have the same alternate_group value in their TrackHeaderBox and any one of these audio tracks
should be included in 'iaug' entity group. A reader processing an 'iaug' entity group should check the
availability of alternative audio tracks in the same file based on the alternate_group syntax element
and select the audio track among the alternatives.
When the FileTypeBox includes a brand specified in this document, and either the file does not include
video or image sequence tracks or when video or image sequence tracks are not played, the playback of
an audio track should only be started when it is present in an 'iaug' entity group and the image item
in the same 'iaug' entity group is displayed. If the image item is a derived image item, only the audio
track that is associated with the final derived image item should be played back, and audio tracks that
are associated with image items utilized during the derivation of the derived image item should not be
played back.
When an audio track is not meant to be played back without the image item associated with the audio
track using the 'iaug' entity group, track_in_movie should be equal to 0 in the TrackHeaderBox of the
audio track.
6.8.5  'ster' entity grouping
'ster': The output images of the image items form a stereo pair suitable for displaying on a stereoscopic
display. The entity group shall contain exactly two entity_id values that point to image items and shall
contain no entity_id values that point to tracks. The first listed entity_id value (with i equal to 0)
indicates the left view and the second entity_id value indicates the right view.
NOTE When a 'ster' entity group indicates that the primary item contains one view of a stereo pair, the
primary item is intended to be displayed in monoscopic viewing of that stereo pair.
6.8.6  Bracketed sets/logically group of images at capture-time
6.8.6.1  Overview
It is useful in some situations to keep and make explicit the relationship between the images for
carrying the initial intent of the photographer during all the photo processing workflow. Image items
and samples from sequence of images ('pict' track) may be logically grouped during capture-time for
many different purposes, for instance, any kind of bracketing such as exposure, white-balance, flash
exposure, depth-of-field, focus.
For this purpose, image items are grouped using an EntityToGroupBox with a specific grouping_type
value that characterizes the purpose of grouping. Samples from images sequences are grouped using
sample grouping with a dedicated grouping_type value and group description that characterize the
purpose of grouping. grouping_type values for bracketed sets defined in this document are listed in
Table 1.
In addition, for each EntityToGroupBox with a given grouping_type value, an item property may be
associated with each item to provide item-specific parameters for this item within the entity group (e.g.
exposure value of an item in an auto exposure bracketing set). The same FourCC code is used for the
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grouping_type of a given EntityToGroupBox and for the box type of the item property that provides the
parameters specific to an item within a corresponding entity group.
NOTE This allows one HEIF reader to easily retrieve the item property associated with a given group of
items among all item properties. (E.g. the parameters of items pertaining to an EntityToGroupBox('aebr') are
provided by an ItemFullProperty('aebr') where 'aebr' is the FourCC for auto exposure bracketing set).
Table 1 — Bracketed set types
grouping_type semantics FourCC codes
aebr
Auto Exposure bracketing
wbbr
White balance bracketing
fobr
Focus bracketing
afbr
Flash Exposure bracketing
dobr
Depth of field bracketing
The following subclauses provide more details on each grouping of images.
6.8.6.2  Auto exposure bracketing
6.8.6.2.1  'aebr' entity group
The auto exposure bracketing entity group ('aebr') indicates a set of image items that were captured
with varying exposure settings. The relative exposure setting for each image item in the entity group
should be defined using an auto exposure item property 'aebr' as specified in subclause 6.5.22.
6.8.6.2.2  'aebr' sample group
6.8.6.2.2.1  Definition
The auto exposure bracketing sample group ('aebr') indicates a set of samples that were captured with
varying exposure settings. There may be several sample groups of type 'aebr', each with a different
value of grouping_type_parameter. AutoExposureBracketingEntry provides the relative exposure
setting for samples associated with this entry in the sample group.
6.8.6.2.2.2  Syntax
aligned(8) class AutoExposureBracketingEntry
extends VisualSampleGroupEntry('aebr') {
int(8) exposure_step;
int(8) exposure_numerator;
}
6.8.6.2.2.3  Semantics
exposure_step is an integer value that specifies the increment steps used during the exposure
bracketing. When equals to 1, a full stop increment is used, when equals to 2, a half stop increment is
used, when equals to 3, a third stop increment is used, and when equals to 4, a quarter stop increment is
used. Other values are reserved.
exposure_numerator is an integer value specifying the exposure numerator used to compute the
exposure value stop of the item.
The exposure value variation of the image item compared to the Automatic Exposure camera settings is
expressed as a number of stops that is computed as exposure_numerator/exposure_step.
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6.8.6.3  White balance bracketing
6.8.6.3.1  'wbbr' entity group
The white balance bracketing entity group ('wbbr') indicates a set of image items that were captured
with varying white balance settings. The relative white balance setting for each image item in the entity
group should be defined using a white balance item property 'wbbr' as specified in subclause 6.5.23.
6.8.6.3.2  'wbbr' sample group
6.8.6.3.2.1  Definition
The white balance bracketing sample group ('wbbr') indicates a set of samples that were captured
with varying white balance settings. There may be several sample groups of type 'wbbr', each with a
different value of grouping_type_parameter. WhiteBalanceBracketingEntry provides the white balance
compensation on blue/amber bias and/or magenta/green bias for samples associated with this entry in
the sample group.
6.8.6.3.2.2  Syntax
aligned(8) class WhiteBalanceBracketingEntry
extends VisualSampleGroupEntry('wbbr') {
unsigned int(16) blue_amber;
int(8) green_magenta;
}
6.8.6.3.2.3  Semantics
blue_amber is an unsigned integer indicating the colour temperature component of the white balance
in Kelvin.
green_magenta is a signed integer indicating the colour deviation component of white balance in unit of
1/100 Duv (distance to the blackbody locus).
NOTE A Duv of 0 indicates a light source that is neutral. A negative Duv indicates a magenta colour shift,
while a positive Duv indicates a green colour shift.
6.8.6.4  Focus bracketing
6.8.6.4.1 'fobr' entity group
The focus bracketing exposure bracketing entity group ('fobr') indicates a set of image items that were
captured with varying focus settings. The relative focus setting for each image item in the entity group
should be defined using a focus item property 'fobr' as specified in subclause 6.5.24.
6.8.6.4.2  'fobr' sample group
6.8.6.4.2.1  Definition
The focus bracketing exposure bracketing sample group ('fobr') indicates a set of samples that were
captured with varying focus settings. There may be several sample groups of type 'fobr', each with a
different value of grouping_type_parameter. FocusBracketingEntry provides the relative focus setting
for samples associated with this entry in the sample group.
6.8.6.4.2.2  Syntax
aligned(8) class FocusBracketingEntry
extends VisualSampleGroupEntry('fobr') {
unsigned int(16) focus_distance_numerator;
unsigned int(16) focus_distance_denominator;
}
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6.8.6.4.2.3  Semantics
The focus distance is expressed in meter as the ratio of focus_distance_numerator and focus_distance_
denominator. Focus at infinity is expressed as division by zero, i.e. focus_distance_denominator is
equal to 0 and focus_distance_numerator should be equal to 0.
6.8.6.5  Flash exposure bracketing
6.8.6.5.1  'afbr' entity group
The flash exposure bracketing entity group ('afbr') indicates a set of image items that were captured
with varying flash exposure settings. The relative flash exposure setting for each image item in the entity
group should be defined using a flash exposure item property 'afbr' as specified in subclause 6.5.25.
6.8.6.5.2  'afbr' sample group
6.8.6.5.2.1  Definition
The flash exposure bracketing sample group ('afbr') indicates a set of samples that were captured
with varying flash exposure settings. There may be several sample groups of type 'afbr', each with
a different value of grouping_type_parameter. FlashExposureBracketingEntry provides the relative
flash exposure setting for samples associated with this entry in the sample group.
6.8.6.5.2.2  Syntax
aligned(8) class FlashExposureBracketingEntry
extends VisualSampleGroupEntry('afbr') {
int(8) flash_exposure_numerator;
int(8) flash_exposure_denominator;
}
6.8.6.5.2.3 Semantics
flash_exposure_numerator and flash_exposure_denominator are integers representing the flash
exposure value of the sample expressed in a number of f-stops as the ratio of flash_exposure_numerator
and flash_exposure_denominator.
6.8.6.6  Depth of field bracketing
6.8.6.6.1  'dobr' entity group
The depth of field bracketing entity group ('dobr') indicates a set of image items that were captured
with varying depth of field settings. The relative depth of field setting for each image item in the entity
group should be defined using a depth of field item property 'dobr' as specified in subclause 6.5.26.
6.8.6.6.2  'dobr' sample group
6.8.6.6.2.1  Definition
The depth of field bracketing sample group ('dobr') indicates a set of samples that were captured
with varying depth of field settings. There may be several sample groups of type 'dobr', each with a
different value of grouping_type_parameter. DepthOfFieldBracketingEntry provides the relative depth
of field setting for samples associated with this entry in the sample group.
6.8.6.6.2.2  Syntax
aligned(8) class DepthOfFieldBracketingEntry
extends VisualSampleGroupEntry('dobr') {
int(8) f_stop_numerator;
int(8) f_stop_denominator;
}
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6.8.6.6.2.3  Semantics
The depth of field variation is expressed as an aperture change in a number of stops, and is computed
as f_stop_numerator/f_stop_denominator.
6.8.7  User-defined image collections
6.8.7.1  'albc' entity group
The album collection entity group ('albc') indicates a set of entities that form an album of images.
Human readable description may be associated with an album collection entity group using a user-
description item property 'udes'.
NOTE Human-readable description with alternatives languages can be obtained by associating multiple
user-description item properties with different lang attributes.
There may be multiple 'albc' entity groupings in the same file with different group_id values, and the
same image may belong to multiple album collections.
6.8.7.2  'favc' entity group
The favourites collection entity group ('favc') indicates a set of entities that form a collection of
favourites images.
Human readable description may be associated with a favourites collection entity group using a user-
description item property 'udes'.
NOTE Human-readable description with alternatives languages can be obtained by associating multiple
user-description item properties with different lang attributes.
There may be multiple 'favc' entity groupings in the same file with different group_id values, and the
same image may belong to multiple favourites collections.
6.8.8  Panorama
6.8.8.1  'pano' entity group
The panorama entity group ('pano') indicates a set of images that were captured in order to create a
panorama.
The entity_id may refer to an item, to a track, or, when unique IDs are used, to another EntityToGroupBox
representing a bracketing set of images.
NOTE The latter is useful to describe enhanced panorama (e.g. an HDR panorama for which each entity
composing the panorama is an auto exposure bracketing entity group 'aebr')
Entities in the panorama entity group or samples in an image sequence track referred by a panorama
entity group are listed in increasing panorama order. The panorama direction (e.g. left-to-right, right-
to-left…) corresponding to the panorama order should be declared using a panorama item property
'pano' associated with the entity group.
When an image sequence track is included in a 'pano' entity group, there shall be only one entity_id
present in the 'pano' entity group. An image sequence track may be included in a 'pano' entity group
to indicate that it contains captured image sequence destined to form a panorama. An image sequence
track present in the 'pano' entity group may contain other bracketing sample grouping (e.g. when the
panorama capture is coupled with an auto exposure bracketing to form an HDR panorama).
There may be multiple 'pano' entity groupings in the same file with different group_id values.
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6.8.8.2  'pano' sample group
6.8.8.2.1  Definition
The panorama sample group ('pano') indicates a set of samples that were captured in order to create a
panorama.
A panorama is composed of frames strictly ordered by increasing frame number. A frame in a panorama
may correspond to one sample or to a set of samples (i.e. samples with same frame number). The
PanoramaEntry provides the frame number within the panorama of samples associated with this entry
in the sample group.
The relationship of samples composing a frame in the panorama may be signalled using a bracketing
sample group (e.g. auto exposure bracketing sample group).
NOTE This is useful to describe enhanced panorama (e.g. an HDR panorama for which each frame
composing the
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