ISO/IEC 23009-1:2014/Amd 3:2016
(Amendment)Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats — Amendment 3: Authentication, MPD linking, Callback Event, Period Continuity and other Extensions
Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats — Amendment 3: Authentication, MPD linking, Callback Event, Period Continuity and other Extensions
Technologies de l'information — Diffusion en flux adaptatif dynamique sur HTTP (DASH) — Partie 1: Description de la présentation et formats de remise des médias — Amendement 3: Authentification, liaison MPD, événement de rapel, continuité de la période et autres extensions
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INTERNATIONAL ISO/IEC
STANDARD 23009-1
Second edition
2014-05-15
AMENDMENT 3
2016-10-15
Information technology — Dynamic
adaptive streaming over HTTP
(DASH) —
Part 1:
Media presentation description and
segment formats
AMENDMENT 3: Authentication, MPD
linking, Callback Event, Period Continuity
and other Extensions
Technologies de l’information — Diffusion en flux adaptatif
dynamique sur HTTP (DASH) —
Partie 1: Description de la présentation et formats de remise des médias
AMENDEMENT 3: Authentification, liaison MPD, événement de rapel,
continuité de la période et autres extensions
Reference number
ISO/IEC 23009-1:2014/Amd.3:2016(E)
©
ISO/IEC 2016
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
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ISO/IEC 23009-1:2014/Amd.3:2016(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
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organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following URL: www.iso.org/iso/foreword.html.
Amendment 3 to ISO/IEC 23009-1:2014 was prepared by ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
© ISO/IEC 2016 – All rights reserved iii
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
Information technology — Dynamic adaptive streaming
over HTTP (DASH) —
Part 1:
Media presentation description and segment formats
AMENDMENT 3: Authentication, MPD linking, Callback Event,
Period Continuity and other Extensions
Page 2, Terms and definitions
Add the following definition in 3.1:
3.1.X
sub-asset
media content component (or part thereof) identified as corresponding to a part of an asset
Page 15, Table 2
Add the following identifiers in Table 2:
Clause in this
Scheme Identifier Informative description
document
urn:mpeg:dash:period-continuity:2015
5.3.2.4 Period continuity signalling
urn:mpeg:dash:period-connectivity:2015
5.3.2.4 Period connectivity
signalling
urn:mpeg:dash:mpd-as-linking:2015
5.8.5.X MPD Adaptation Set
Linking scheme.
urn:mpeg:dash:sai:2015
5.8.5.Y Sub-Asset Scheme Identifier
urn:mpeg:dash:client-authentication:2015
5.8.5.Z Client Authentication
scheme.
urn:mpeg:dash:content-authorization:2015
5.8.5.Z Content Access
Authorization scheme.
urn:mpeg:dash:event:callback:2015
5.10.4.X DASH call back event.
Page 9, Clause 4
Add in the second paragraph of 4.3, discussing Assets:
Same asset over multiple periods may be identified by a DASH descriptor enabling DASH clients to
maintain the continuity across periods’ boundaries. Furthermore, sub-assets composing the same
asset may also identified using a similar method. For instance, if an asset is composed of multiple video
components, sub-assets enable selecting the previously selected video component after an ad insertion.
As such an asset can contain sub-assets that can be uniquely identified from one media content period
to another.
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
Page 23, Table 4
Add at the end of Table 4:
EmptyAdaptationSet
0.N specifies an Adaptation Set that does not contain any
Representation element. The empty Adaptation Set is
of the same type as a regular Adaptation Set, but shall
neither contain an xlink nor may it contain any Rep-
resentation element.
This element shall only be present, if an Essential
Descriptor is present with @schemeIDURI set to
“urn:mpeg:dash:mpd-as-linking:2015”.
For more details, see 5.8.5.8.
Page 25, Clause 5
Add to schema:
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
Page 25, Clause 5
Add new subclause:
5.3.2.4 Content Offering with multiple Periods
Content with multiple Periods may be created for different reasons, for example:
— to enable splicing of content, for example for ad insertion;
— to provide synchronization in segment numbering, e.g. compensate non-constant segment durations;
— to remove or add certain Representations in an Adaptation Set;
— to remove or add certain Adaptation Sets;
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
— to remove or add content offering on certain CDNs;
— to enable signalling of shorter segments, if produced by the encoder.
Periods provide opportunities for resync, for ad insertion, for adding and removing Representations.
However, in certain circumstances, the content across Period boundaries is continuous and in this case,
continuous playout of the client is expected.
In certain circumstances, the Media Presentation is offered such that the next Period is a continuation
of the content in the previous Period (certain media components are continued), possibly in the
immediately following Period of that previous Period or in a later Period (e.g. after an advertisement
Period had been inserted).
The content provider may express that the media components contained in two Adaptation Sets in
two different Periods are associated by assigning equivalent Asset Identifiers to both Periods and by
identifying both Adaptation Sets with identical value for the attribute @id. Association expresses a
logical continuation of the media component in the next Period and may, for example, be used by the
client to continue playing an associated Adaptation Set in the new Period.
In addition, two Adaptation Sets in one MPD are period-continuous if all of the following holds.
— The Adaptation Sets are associated.
— The sum of the value of the @presentationTimeOffset and the presentation duration of the
Representations in one Adaptation Set are identical to the value of the @presentationTimeOffset
of the associated Adaptation Set in the next Period.
— If Representations in both Adaptation Sets have the same value for @id, then they shall have
functionally equivalent Initialization Segments, i.e. the Initialization Segment may be used to
continue the play-out of the Representation. The concatenation of the Initialization Segment of the
first Period, if present, and all consecutive Media Segments in the Representation in the first Period
and subsequently the concatenation with all consecutive Media Segments in the Representation of
the second Period shall represent a conforming Segment sequence as defined in 4.5.4 conforming to
the media type as specified in the @mimeType attribute for the Representation in the first Period.
Additionally, the @mimeType attribute for the Representation in the next Period shall be the same
as one of the first Period.
Media Presentations should signal period-continuous Adaptation Sets by using a supplemental
descriptor on Adaptation Set level with @schemeIdUri set to “urn:mpeg:dash:period-
continuity:2015” with
— the @value of the descriptor matching the value of an @id of a Period that is contained in the
MPD, and
— the value of the AdaptationSet@id being the same in both Periods.
MPD should signal period-continuous Adaptation Sets if the MPD contains Periods with identical Asset
Identifiers.
There exist special cases, for which the media in one Adaptation Set is a continuation of the previous
one, but the timestamps are not continuous. Examples are timestamp wrap around, encoder reset,
splicing, or other aspects. Two Adaptation Sets in one MPD are period-connected if all conditions
from period-continuity from above hold, except that the timestamps across Period boundaries may
be non-continuous, but adjusted by the value of the @presentationTimeOffset at the Period
boundary. However, for example, the Initialization Segment is equivalent within the two Adaptation
Sets. Media Presentations should signal period-connected Adaptation Sets by using a supplemental
descriptor on Adaptation Set level with @schemeIdUri set to “urn:mpeg:dash:period-
connectivity:2015”.
Note that period continuity implies period connectivity.
For appropriate client behaviour, please refer to A.9.
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
Page 74, Clause 5
Add new subclause:
5.8.5.X DASH MPD Adaptation Set Linking scheme
The URN “urn:mpeg:dash:mpd-as-linking:2015” is defined in order to provide information
that the same Adaptation Set can be found in another MPD. The scheme may be used with Essential
Property Descriptors together with an EmptyAdaptationSet element or with Supplemental
Property Descriptors. The value provides
— a URL to the MPD, including appropriate anchors for Periods and Adaptation Set as defined in
C.4.2, and
— optionally, a timeline offset field to synchronize the data added as a white-space separated second
item. If the value is not present, then the media time on the original MPD and the linked MPD are
identical. If a timeOffset field is added, then this value expresses the difference between the
media time of the Adaptation Set of the linked MPD and the media time in the originating MPD. Note
that the number may be positive or negative. The timeoffset is in unit of @timescale of the
linked Adaptation Sets.
The Descriptor shall only be used in combination with Adaptation Sets (regular or empty ones). If
all information is contained in the Adaptation Set, then a Supplemental Descriptor or an Essential
Descriptor may be used. If the Adaptation Set does neither contain a Representation element, nor
an @xlink attribute, then an Empty Adaptation Set as well as an Essential Descriptor shall be used to
indicate that the Adaptation Set is not fully described in this MPD.
NOTE This scheme may be used for many use cases. However, one specific use case is the server-based
mosaic channel as described in ISO/IEC 23009-3. The use case may be fulfilled by the combination of the Spatial
Relationship Description (SRD) as defined in Annex H and this scheme.
Page 74, Clause 5
Add new subclause:
5.8.5.Y Sub-Asset Scheme Identifier
In DASH MPD, sub-assets across Periods can be identified using the sub asset Scheme Identifier. This
scheme is signalled using a specific SupplementalProperty descriptor at the Adaptation Set or Sub-
Representation level with @schemeIdUri attribute set to “urn:mpeg:dash:sai:2015”.
If two different Adaptation Sets or Sub-Representation from different Periods contain Sub-Asset
Identifiers descriptors with the same @value attribute, then the content in the Representation(s)
contained in these Adaptation Sets represent, at least, the same sub-asset.
NOTE 1 The association between sub-assets and an Adaptation Set may change between Periods. For instance,
an Adaptation Set may be associated with a sub-asset of an asset in one Period but with another sub-asset of the
same asset in another Period.
NOTE 2 Sub-Asset Identifier descriptor may be used by DASH clients to select Representation(s) to be
processed after a Period change.
A given Adaptation Set may contain more than one Sub-Asset Identifier descriptor indicating that the
Representation(s) contained in this Adaptation Set represent more than one identified part of the asset.
NOTE 3 If the value for this descriptor is not recognized, the SubAsset Identifier descriptor may still be used
to understand the equivalence of sub-asset identifiers across Periods. Processing of the descriptor scheme and
value by the DASH client is not essential for normal operation.
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
Page 74, Clause 5
Add new subclause:
5.8.5.Z Client Authentication and Content Access Authorization
When client authentication and/or content access authorization functionality is needed, DASH may
be used with different schemes, such as Open Authentication Technical Committee (OATC) Online
[13] [14]
Multimedia Authorization Protocol (OMAP), Open Standard for Authorization (OAuth) 2.0, OASIS
[15] [16]
Security Assertion Markup Language (SAML), 3GPP Generic Authentication Architecture (GAA),
[17]
or 3GPP Generic Bootstrapping Architecture (GBA). This subclause describes generic signalling to
support use of various authentication and authorization schemes.
Typical access control methods include blocking HTTP requests that do not include a security token
obtained by the authorization protocol wherein the security token is validated by a CDN before
downloading the requested Media Segment, or encrypting Media Segments so that playback will be
restricted unless the authorization protocol provides the client with a decryption key.
For client authentication, a service may limit content delivery to authenticated clients and may use
client identification information such as certificates, cookies, and embedded keys to determine
subscription rights, etc. required to authorize playback of the Media Presentation. The details of such
a scheme are outside the scope of this document. A client that does not support the signalled content
access authorization would not be able to play the content.
NOTE This subclause does not provide any requirements on client authentication or content access
authorization.
The signalling and setup of the specific scheme may be done outside the MPD level, e.g. a system
applying such a scheme may only permit access to the MPD if the client is authenticated or the content
access is authorized.
However, there are cases for which the MPD is provided without access control. In this case, client
authentication and content access authorization methods may be signalled in the MPD using
Essential Property Descriptors. The DASH client may be offered with multiple options to access
the entire Media Presentation or specific parts of the Media Presentation, e.g. a specific Adaptation
Set. An Essential Property descriptor may be placed at the appropriate level, and, for example, the
EssentialProperty@schemeIdUri may signal the URN of the appropriate authentication or
authorization method and the EssentialProperty@value attribute may carry some scheme
specific information. Other signalling may be used, but the detailed signalling and semantics remain
specific to a particular scheme.
There may be cases in which multiple options are provided to the client for client authentication and/or
content access authorization. In this case, the EssentialProperty@id value may be used to signal
functional equivalence of descriptors. In the absence of other information, the EssentialProperty@
id value may contain the following URNs:
— urn:mpeg:dash:client-authentication:2015 for client authentication;
— urn:mpeg:dash:content-authorization:2015 for content access authorization.
In this case,
— each EssentialProperty descriptor with EssentialProperty@id value of
urn:mpeg:dash:client-authentication:2015 indicates a supported client authentication
protocol. A client may select one of possibly multiple elements with that EssentialProperty@
id value and a scheme that it recognizes based on the @schemeIdUri attribute; and execute
that protocol using any information included in the @value attribute and any extension elements
defined by that particular authentication scheme;
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
— each EssentialProperty descriptor with EssentialProperty@id value of
urn:mpeg:dash:content-authorization:2015 indicates a supported content
access authorization protocol. A client may select one of possibly multiple elements with that
EssentialProperty@id value and a scheme that it recognizes based on the @schemeIdUri
attribute; and execute that protocol using any information included in the @value attribute and
any extension elements defined by that particular authorization scheme.
A DASH client that is successfully authenticated as an authenticated player and authorized for playback
of some or all Representations or Adaptation Sets in the MPD may request and play the authorized
content.
Page 74, Clause 5
Add new subclause:
5.10.4.X DASH Callback Event
5.10.4.X.1 General
DASH Callback events are indications in the content that it is expected by a DASH client to issue an
HTTP GET request to a given URL and ignore the HTTP response. These event schemes are identified by
the URN “urn:mpeg:dash:event:callback:2015”.
A content author may use such an event for tracking play-back of specific content on a server that is not
included in the media path.
The Status-Code field of the HTTP response should be 2xx, however the client is expected to entirely
ignore the response.
[18]
NOTE 1 HTTP GET (as opposed to HEAD) is used in alignment with IAB VAST.
The message body of the HTTP response should be as small as possible or absent.
NOTE 2 The system adopting this functionality is expected to define appropriate means for secure handling of
this feature.
5.10.4.X.2 Inband event
Table 5.10.4.X.1 defines the message data and the expected actions for different @value values when
the DASH callback event is signalled as an Inband Event.
Table 5.10.4.X.1 — Message data and expected actions for DASH call back inband event
value message_data[]
Action
1
Valid HTTP/HTTPS URL An HTTP GET request is expected to be issued to a
URL contained in message_data[].
The URL shall be a NULL-terminated string.
HTTP response shall either not be provided or be
provided such that it can be discarded.
5.10.4.X.3 MPD event
Table 5.10.4.X.2 defines the relevant parameters for a call back event signalled in the MPD.
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
Table 5.10.4.X.2 — Relevant parameters for a call back event signalled in the MPD
Attribute Value
”urn:mpeg:dash:event:callback:2015”
EventStream@schemeIdUri
EventStream@value 1
Event@messageData
HTTP-URL
HTTP response is expected to be discarded without
parsing.
Page 114, Annex A
Add new A.9:
A.9 Playback across Period boundaries
From a client perspective, Period boundaries may require processing that makes fully continuous playout
impossible or at last practically complex. For example, the content may be offered with different codecs,
different language attributes, different protection and so on. The client is expected to play the content
continuously across Periods, but there may be implications in terms of implementation to provide fully
continuous and seamless playout. It may be the case that at Period boundaries, the presentation engine
needs to be re-initialized, for example due to changes in formats, codecs or other properties. This may
result in a re-initialization delay. Such a re-initialization delay should be minimized.
If the client presents media components of a certain Adaptation Set with a specific value foo for
the AdaptationSet@id in one Period, and if the following Period has assigned an identical Asset
Identifier, then the client is suggested to identify an associated Period and, in the absence of other
information, continue playing the content in the associated Adaptation Set, i.e. the Adaptation Set with
value foo for the AdaptationSet@id.
If the client presents media components of a certain Sub-Representation in one Period, and if the
following Period has assigned an identical Sub-Asset Identifier, then the client is suggested to identify
an associated Period and, in the absence of other information, continue playing the content in the
associated Sub-Representation.
If furthermore the Adaptation Sets are period-continuous or period-connected as defined in 5.3.2.4, i.e.
the presentation times are continuous and this is signalled in the MPD, then the client is expected to
seamlessly play (as defined in 4.5.1) the content across the Period boundary. Most suitably, the client may
continue playing the Representation in the Adaptation Set with the same @id, but there is no guarantee
that this Representation is available. In this case, the client is expected to seamlessly switch (as defined
in 4.5.1) to any other Representation in the Adaptation Set. If period continuity is signalled and if
continuously playing, then the client should ignore the value of the @presentationTimeOffset
attribute and just continuing processing the incoming Segments. If period connectivity is signalled
and if continuously playing, then the client is expected to inform the media decoder on a timeline
discontinuity obeying the value of @presentationTimeOffset attribute, but it may continuing
processing the incoming Segments without, for example, re-initializing the media decoder.
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
Page 115, Annex B
Update Annex B:
Annex B
(normative)
MPD schema
The schema of the MPD for this edition of the document is provided below.
attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.
w3.org/2001/XMLSchema" xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns="urn:mpeg:dash:schema:mpd:2011">
Media Presentation Description
This Schema defines the Media Presentation Description for MPEG-DASH.
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
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ISO/IEC 23009-1:2014/Amd.3:2016(E)
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
maxOccurs="unbounded"/>
...
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