ANSI SCTE 223-2018 pdf free download – Adaptive Transport Stream.
5 ATS METADATA OVERVIEW
ATS Metadata refers to a description of the ATS bitstream. Metadata can be categorized as:
• static metadata, where the description remains the same over the entire bitstream; for example, structural metadata describing the number of ATS streams and their relationships
• time-variant metadata, where the description can vary and change at different points of relative time in the bitstream, (either stream or wall clock time), for example EBP structures describing chunk boundaries
• event metadata, such as ad insertion points or program start/end.
ATS supports several mechanisms to carry this metadata. In the elementary stream, metadata can be carried through the EBP structure, located in its transport MPEG packet header, which can convey time variant metadata such as location of chunk boundaries in the stream, types of chunks, and chunk labels as well as wall-clock media time at chunk boundaries. In the transport stream, the PMT descriptors can describe metadata at the transport level and elementary stream level and can describe PID, stream type (video descriptor, audio descriptor, captioning, language, bandwidth), and supported chunk cadences through the EBP PMT descriptor. The PMT information is usually static until a major event that changes the media experience occurs in the stream. Lastly, event metadata can be conveyed through the SCTE 35 descriptors and triggers (see Section 8.5) or through a private metadata mechanism on a separate pid (see Section 7.14.1). The information carried is used to indicate alternate content such as ad insertion, campaigns, and blackout events. Additionally, static metadata is carried out of band or alternatively inband in the ATS Source Description (see Section 0).
6 ATS soURCE DESCRIPTION6.1 lntroduction
An ATS Source Description is used to describe the properties of a set of related ATSs. The primary use of the ATSSource Description is to provide information about the location of the source ATSs, for example a set of multicastaddresses for a group of ATSs that are intended to be combined into a DASH AdaptationSet. It carries static
metadata in addition to content source location such as program service metadata,MPEG-2 TS structure andattributes, etc. This metadata may be used by downstream devices to configure packaging or recording tasks.The ATS Source Description follows the MPD schema of MPEG DASH [14] with enhancements to describesources that are streams rather than files.
The information conveyed by an ATS Source Description should be created while or before the media transcodingtask is started.ATS Source Description may be updated at a programming boundary. The publication and delivery ofATS Source Description is beyond the scope of this specification.
All restrictions and extensions defined in SCTE214-1 [8] and SCTE 214-2[9] shall apply.
Extensions and restrictions specified in section 0 of this apply to an MPD otherwise compliant to SCTE 214-1 [8]and SCTE 214-2 [9].ATS source description is thus based on the DASH/TS profile as defined in SCTE 214-1[8]and SCTE 214-2[9] but is not a proper subset of it.Hence there should be no expectation on behalf of DASHTSclient to be able to present it.
6.2ldentification
ATS Source Description document is a DASH MPD document with MPD@profiles value”urn:scte:ats:source:2015″.
6.3Non-HTTP URIs6.3.1General
ISO/IEC 23009-1 limits BaseURL values to HTTP(S)URLs only.
ATS Source Description require support for file : / / and udp : / / schemes in addition to HTTP(S).When multiple URl schemes are used simultaneously, BaseURL shall not be present at any level except forRepresentation.
6.3.2MPEG-2 Ts over UDP
A URl with scheme value “udp ” identifies an MPEG-2 TS packets embedded into UDP.The udp:!/ scheme syntax is as follows:
udp: i i [<localaddress>@ ]<destination | multicastgroup> [ :<port>]
Each UDP packet typically contains 1 to 7 complete 188 byte TS packets with no additional headers or footers.Thisis consistent with the definition of the scheme given by http:/www.iana.org/assignments/uri-schemes/prov/udp.NOTE: local address corresponds to the multicast source
Each UDP packet payload contains only complete MPEG-2 TS packets6.3.3 File
File URl format is defined in Uniform Resource ldentifier(URI): Generic Syntax[7].ANSI SCTE 223 pdf download.