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2.2.7.3.1 LiveSMIL

The LiveSMIL and related fields comprise the data required for the client to identify all the streams in a presentation.

SMIL (variable): The root container used by SMIL 2.0 [SMIL2.1]. The xmlns field MUST be set to http://www.w3.org/2001/SMIL20/Language.

SMILLiveHead (variable): The head element that contains the presentation-level metadata.

SMILLiveMeta (variable): The metadata of the presentation. The following attributes are supported:

  • name: Specifies the semantic meaning of metadata; this attribute MUST be present.

  • content: Specifies the value of metadata; this attribute MUST be present.

SMILLiveBody (variable): The body element contains track information and references to other media.

SMILTrack (variable): One of the comprising tracks in the presentation. Can be video, audio, or text. The following attributes are supported:

  • src: Specifies the file in which the track resides. This attribute is optional. For all Live Smooth Streaming manifests, the src attribute SHOULD be set to "Streams".

  • systemBitrate: Specifies the bit rate of the track; this attribute MUST be present.

SMILParam (variable): Specifies a single parameter for a given SMILTrack. The following attributes are supported:

  • name: Specifies the name of the parameter; this attribute MUST be present.

  • value: Specifies the parameter’s value; this attribute MUST be present.

  • valuetype: Specifies "type" of value attribute; this attribute MUST be present. The valuetype attribute MUST be set to "data".

The valid range and semantic meaning of the name and value attributes varies as described below, depending on the value of the name attribute:

name

value

trackID (required)

A required attribute that MUST be present. It specifies the ID of the track containing the video, audio, or textstream element described. This value correlates to the track_ID field in the tfhd and trak boxes for the track.

trackName

An optional parameter that specifies the client-facing name of the track, and appears in the Fragments() noun as part of the URL. All the tracks that have the same value for systemBitrate and attributes MUST have distinct track names. If this parameter is omitted, the following default track names are assigned by IIS:

  • video tracks: value="video"

  • audio tracks: value="audio"

  • textstream tracks: value="textstream"

manifestOutput

An optional parameter that specifies whether or not sample data for the given track is accumulated into the manifest, and therefore made immediately available to the client. Valid values for this parameter are TRUE or FALSE. If omitted, the default value is FALSE and sample data is not accumulated in the manifest.

parentTrackName

An optional parameter that identifies the track as being a sparse track and also specifies the name of its parent track. If this track is a control track, its data is downloaded transparently with the data from the parent track. Valid values for this parameter are trackName parameters for other tracks in the presentation. The tracks referenced by parentTrackName MUST NOT be control tracks, and MUST NOT be sparse tracks.

{namepace}_{custom attribute}

An optional parameter allowing the definition of additional extended attributes for a track. The namespace and custom_attribute are defined on a per-use basis with the brackets omitted. This parameter can be used to discriminate between tracks having the same track name and bit rate.

timescale

An optional parameter that specifies the timescale for this track, as the number of units that pass in one second. If this parameter is not present, the default value used is 10,000,000, which maps to increments of 100ns.

Subtype

An optional parameter that specifies information that can be used by the client to identify characteristics of the track.

The syntax of the fields defined in this section, specified in ABNF [RFC5234], is as follows:

SMIL = "<" SMILMediaElementName SMILMediaNamespace ">" S?
        SMILLiveHead S SMILLiveBody S?
       "</" SMILMediaElementName ">"
SMILMediaElementName = "smil"
SMILMediaNamespace = "xmlns" Eq DQ "http://www.w3.org/2001/SMIL20/Language" DQ 
SMILLiveHead = "<head"> S SMILLiveMeta S "</head>"
SMILLiveMeta = "<meta " S "name" Eq DQ IDENTIFIER DQ S "content" Eq DQ IDENTIFIER DQ S?
               "/>"
SMILLiveBody = "<body>" S "<switch>" S SMILTracks S "</switch"> S "</body>"
SMILTracks = 1*(SMILVideoTrack / SMILAudioTrack / SMILTexttrack)
SMILVideoTrack = ="<video S SMILTrackAttributes S ">" S 1*SMILParam S "</video>"
SMILAudioTrack ="<audio S SMILTrackAttributes S ">" S 1*SMILParam S "</audio>"
SMILTextTrack = ="<textstream S SMILTrackAttributes S ">" S 1*SMILParam S "</textstream>"
SMILTrackAttributes = "src" S Eq S DQ "Streams" DQ S "systemBitrate" S Eq S DQ
                       1*DIGIT DQ S ">" 
SMILParam = "<param" S "name" Eq DQ IDENTIFIER DQ S "value" Eq DQ IDENTIFIER DQ S?
            "valuetype" Eq DQ "data" DQ S "/>"
 
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