1、INTERNATIONAL STANDARD ISO/IEC 23009-1:2014 TECHNICAL CORRIGENDUM 1 Published 2015-04-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION LECTROTECHNIQUE INTERNATIONALE Information technology Dynamic adap
2、tive streaming over HTTP (DASH) Part 1: Media presentation description and segment formats TECHNICAL CORRIGENDUM 1 Technologies de linformation Diffusion en flux adaptatif dynamique sur HTTP (DASH) Partie 1: Description de la prsentation et formats de remise des mdias RECTIFICATIF TECHNIQUE 1 Techni
3、cal Corrigendum 1 to ISO/IEC 23009-1:2013 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information. Replace 4.5.1 Switching and Random Access Support The formats defined in this part of the st
4、andard are designed for providing good user experience even in case the access bandwidth of the DASH segment delivery or the cache varies. A key functionality is the ability that the DASH client can seamlessly switch across different Representations of the same media component. DASH clients may use
5、the common timeline across different Representation representing the same media component to present one Representation up to a certain time t and continue presentation of another Representation from time t onwards. However, in practical implementations, this operation may be complex, as switching a
6、t time t may require parallel download and decoding of two Representations. Therefore, providing suitable switching opportunities in regular time intervals simplifies client implementations. The ICS 35.040 Ref. No. ISO/IEC 23009-1:2014/Cor.1:2015(E) ISO/IEC 2015 All rights reserved Published in Swit
7、zerlandISO/IEC 23009-1:2014/Cor.1:2015 (E) 2 ISO/IEC 2015 All rights reservedstandard provides means for providing suitable switching opportunities and in addition provides abilities to signal the position and media time of the switching opportunities. For this purpose this subsection defines three
8、relevant concepts to support seamless switching, namely Media stream access points in 4.5.2 to signal positions where to easily switch to a Representation, and in addition where to suitable access a Representation at start-up or seek. Non-overlapping Segments and Subsegments in 4.5.3 to signal that
9、at the signalled stream access points, no overlap decoding of Representations is necessary in order to provide a continuous switch Bitstream concatenation in 4.5.4 to signal that the concatenation of two Representations at a switch point results in a conforming bitstream These three properties are n
10、either sufficient nor necessary for seamless switching, but certain implementation or profiles may use these properties in order to simplify practical implementations. with 4.5.1 Switching and Random Access Support The formats defined in this part of the standard are designed for providing good user
11、 experience even in case the access bandwidth between the DASH segment delivery function or the cache varies. A key functionality is the ability that the DASH client can seamlessly switch across different Representations of the same media component without severely impacting the user experience. Ass
12、ume two Representations A and B. A switch from Representations A to Representation B at media time t is considered seamless, if the result of the presentation a fter this switch is applied is identical as if Representation A is decoded from the beginning and presented up to time t and Representation
13、 B is decoded from the beginning and presented from time t onwards. Media Presentations may provide different Representations in one Adaptation Set representing the same media component. If such Representations are properly time-aligned (as expected by the Media Presentation), then DASH clients may
14、apply seamless switching across different Representations provided in one Adaptation Set at any time t to obtain a perceptually continuous experience. However, in practical implementations, the operation of seamless switching may be complex, as switching at time t may require parallel download and d
15、ecoding of two Representations. Therefore, providing suitable switching opportunities in regular time intervals simplifies client implementations. This part of ISO/IEC 23009- 1 provides means for providing suitable switching opportunities and in addition provides abilities to signal the position and
16、 media time of the switching opportunities. For this purpose this subsection defines three relevant concepts to support seamless switching: Media stream access points in 4.5.2 to signal positions where to easily switch to a Representation, and in addition where to suitable access a Representation at
17、 start-up or seek. Non-overlapping Segments and Subsegments in 4.5.3 to signal that at the signalled stream access points, no overlap decoding of Representations is necessary in order to provide a continuous switch. Bitstream concatenation in 4.5.4 to signal that the concatenation of two Representat
18、ions at a switch point results in a conforming bitstream. These three properties are neither sufficient nor necessary for seamless switching, but certain implementation or profiles may use these properties in order to simplify practical implementations. ISO/IEC 23009-1:2014/Cor.1:2015 (E) ISO/IEC 20
19、15 All rights reserved 3In 4.7 Schemes, Table 2 replace urn:mpeg:dash:23003:3:audio_chan nel_configuration:2011 5.8.5.4 channel configuration. urn:mpeg:dash:outputChannelPosit ionList:2012 5.8.5.4 a list of output channel position to signal individual speaker positions as defined in ISO/IEC 23001-8.
20、 With urn:mpeg:dash:23003:3:audio_chan nel_configuration:2011 5.8.5.4 channel configuration. NOTE: legacy format for backward-compatibility, it is recommended to use the signaling as defined in ISO/IEC 23001-8 instead. urn:mpeg:dash:outputChannelPosit ionList:2012 5.8.5.4 a list of output channel po
21、sition to signal individual speaker positions as defined in ISO/IEC 23001-8. NOTE: legacy format for backward-compatibility, it is recommended to use the signalling as defined in ISO/IEC 23001-8 instead. ISO/IEC 23009-1:2014/Cor.1:2015 (E) 4 ISO/IEC 2015 All rights reservedIn 5.2.3.2 Elements and At
22、tributes added in this Revision replace This revision adds the following elements and attributes to the schema defined in Annex B compared to the 2012 revision (ISO/IEC 23009-1:2012/Cor 1:2013) of this part of the standard: MPDpublishTime Period.AssetIdentifier Period.EventStream RepresentationBase.
23、InbandEventStream SegmentBaseavailabilityTimeOffset SegmentBaseavailabilityTimeComplete BaseURLavailabilityTimeOffset BaseURLavailabilityTimeComplete Subsetid with This revision adds the following elements and attributes to the schema defined in Annex B compared to the 2012 revision (ISO/IEC 23009-1
24、:2012/Cor 1:2013) of this part of the standard: MPDpublishTime MPD.EssentialProperty MPD.SupplementalProperty Period.AssetIdentifier Period.EventStream Period.SupplementalProperty RepresentationBase.InbandEventStream SegmentBaseavailabilityTimeOffset SegmentBaseavailabilityTimeComplete BaseURLavaila
25、bilityTimeOffset BaseURLavailabilityTimeComplete Subsetid SegmentTimeline.Sn ISO/IEC 23009-1:2014/Cor.1:2015 (E) ISO/IEC 2015 All rights reserved 5In 5.3.1.2 Semantics, Table 3 add at the end EssentialProperty 0 N specifies information about the containing element that is considered essential by the
26、 Media Presentation author for processing the containing element. For details see 5.8.4.8. SupplementalProperty 0 N specifies supplemental information about the containing element that may be used by the DASH client optimizing the processing. For details see 5.8.4.9. ISO/IEC 23009-1:2014/Cor.1:2015
27、(E) 6 ISO/IEC 2015 All rights reservedIn 5.3.1.3 XML syntax replace with ISO/IEC 23009-1:2014/Cor.1:2015 (E) ISO/IEC 2015 All rights reserved 7ISO/IEC 23009-1:2014/Cor.1:2015 (E) 8 ISO/IEC 2015 All rights reservedIn 5.3.2.1 Overview replace A Media Presentation consists of one or more Periods. A Per
28、iod is defined by a Period element in the MPD element. The type of the Period, either a regular Period or an Early Available Period, as well as the PeriodStart time of a regular Period is determined as follows: If the attribute start is present in the Period, then the Period is a regular Period and
29、the PeriodStart is equal to the value of this attribute. If the start attribute is absent, but the previous Period element contains a duration attribute then this new Period is also a regular Period. The start time of the new Period PeriodStart is the sum of the start time of the previous Period Per
30、iodStart and the value of the attribute duration of the previous Period. If (i) start attribute is absent, and (ii) the Period element is the first in the MPD, and (iii) the MPDtype is static, then the PeriodStart time shall be set to zero. If (i) start attribute is absent, and (ii) the previous Per
31、iod element does not contains a duration attribute or the Period element is the first in the MPD, and (iii) the MPDtype is dynamic, then this Period is an Early Available Period (see below for details). For any regular Period the following holds: PeriodStart reflects the actual time that should elap
32、se after playing the media of all prior Periods in this Media Presentation relative to the PeriodStart time of the first Period in the Media Presentation. The Period extends until the PeriodStart of the next Period, or until the end of the Media Presentation in the case of the last Period. More spec
33、ifically, the difference between the PeriodStart time of a Period and either the PeriodStart time of the following Period, if this is not the last Period, or the value of the MPDmediaPresentationDuration if this is the last one, is the presentation duration in Media Presentation time of the media co
34、ntent represented by the Representations in this Period. Early Available Periods may be used to advertise initialization of other non-media data before the media data itself is available. Period elements documenting early available Periods shall not occur before any Period element documenting a regu
35、lar Period. For Early Available Periods, any resources that are announced in such a Period element shall be available. Such a Period element shall not contain URLs to Media Segments. The data contained in such a Period element does not represent a Period in the Media Presentation. Only when the Peri
36、odStart time becomes known through an update of the MPD, such a Period element represents a regular Period. However, an update of the MPD may even remove a Period element representing an Early Available Period in later updates of the MPD as long as no PeriodStart time is associated with the Period.
37、with A Media Presentation consists of one or more Periods. A Period is defined by a Period element in the MPD element. Three types of Periods are defined: Regular Period, Early Available Period, Early Terminated Period. The type of the Period, as well as the PeriodStart time of a regular Period or e
38、arly terminated Period is determined as follows: If the attribute start is present in the Period, then the Period is a regular Period or an early terminated Period and the PeriodStart is equal to the value of this attribute. If the start attribute is absent, but the previous Period element contains
39、a duration attribute then this new Period is also a regular Period or an early terminated Period. The start time of the new Period PeriodStart is the sum of the start time of the previous Period PeriodStart and the value of the attribute duration of the previous Period. ISO/IEC 23009-1:2014/Cor.1:20
40、15 (E) ISO/IEC 2015 All rights reserved 9 If (i) start attribute is absent, and (ii) the Period element is the first in the MPD, and (iii) the MPDtype is static, then the PeriodStart time shall be set to zero. If (i) start attribute is absent, and (ii) the previous Period element does not contain a
41、duration attribute or the Period element is the first in the MPD, and (iii) the MPDtype is dynamic, then this Period is an Early Available Period (see below for details). If (i) duration attribute is present, and (ii) the next Period element contains a start attribute or the minimumUpdatePeriod is p
42、resent, then this Period is an Early Terminated Period (see below for details). For any regular Period and early terminated Period the following holds: PeriodStart reflects the actual time that should elapse after playing the media of all prior Periods in this Media Presentation relative to the Peri
43、odStart time of the first Period in the Media Presentation. The Period extends until the PeriodStart of the next Period, or until the end of the Media Presentation in the case of the last Period. For regular Periods, the difference between the PeriodStart time of a Period and either the PeriodStart
44、time of the following Period, if this is not the last Period, or the value of the MPDmediaPresentationDuration if this is the last one, is the presentation duration in Media Presentation time of the media content represented by the Representations in this Period. For Early Terminated Periods, the va
45、lue of the Periodduration is the presentation duration in Media Presentation time of the media content represented by the Representations in this Period. Early Available Periods may be used to advertise initialization of other non-media data before the media data itself is available. Period elements
46、 documenting early available Periods shall not occur before any Period element documenting a regular Period. For Early Available Periods, any resources that are announced in such a Period element shall be available. The data contained in such a Period element does not represent a Period in the Media
47、 Presentation. Only when the PeriodStart time becomes known through an update of the MPD, such a Period element represents a regular Period. However, an update of the MPD may even remove a Period element representing an Early Available Period in later updates of the MPD as long as no PeriodStart tim
48、e is associated with the Period. ISO/IEC 23009-1:2014/Cor.1:2015 (E) 10 ISO/IEC 2015 All rights reservedIn 5.3.2.2 Semantics replace Table 4 Semantics of Period element Element or Attribute Name Use Description Period specifies the information of a Period. xlink:href O specifies a reference to a remote element entity that is either empty or contains one or multiple top-level elements of type Period xlink:actuate OD default: onRequest specifies the processing instructions, which can be either “onLoad“ or “onRequest“. This attribute shall not be pres
