instantiationEssenceTrack is an XML container element that allows for grouping of related essenceTrack elements and their repeated use. Use instantiationEssenceTrack element to describe the individual streams that comprise an instantiation, such as audio, video, timecode, etc.
Best practice: Essence tracks can exist in either the digital or physical realm. In the digital realm, they may refer to the separate audio and video tracks within a digital file. In the physical realm, they may refer to the video and audio tracks contained on a single video tape.
Usage: optional, repeatable.
instantiationEssenceTrack has no attributes.
instantiationEssenceTrack contains the following subelements:
- essenceTrackType – optional. The essenceTrackType element refers to the media type of the decoded data. Tracks may possibly be of these types: video, audio, caption, metadata, image, etc.
- essenceTrackStandard – optional. The essenceTrackStandard element should be be used with file-based instantiations to describe the broadcast standard of the video signal (e.g. NTSC, PAL) or to further clarify the standard of the essenceTrackEncoding format.
- essenceTrackEncoding – optional. The essenceTrackEncoding element identifies how the actual information in an instantiation is compressed, interpreted, or formulated using a particular scheme. Identifying the encoding used is beneficial for a number of reasons, including as a way to achieve reversible compression; for the construction of document indices to facilitate searching and access; or for efficient distribution of the information across data networks with differing bandwidths or pipeline capacities. Human-readable encoding value should be placed here. Use @ref to identify the codec ID.
- essenceTrackDataRate – optional. The essenceTrackDataRate element measures the amount of data used per time interval for encoded data. The data rate can be calculated by dividing the total data size of the track’s encoded data by a time unit. By default use bytes per second.
- essenceTrackFrameRate – optional. The essenceTrackFrameRate element is relevant to tracks of video track type only. The frame rate is calculated by dividing the total number of frames by the duration of the video track. By default measure frame rate in frames per second expressed as fps as a unit of measure. e.g., 24 fps.
- essenceTrackPlaybackSpeed – optional. The essenceTrackPlaybackSpeed element specifies the rate of units against time at which the media track should be rendered for human consumption. e.g., 15ips (inches per second).
- essenceTrackSamplingRate – optional. The essenceTrackSamplingRate element measures how often data is sampled when information from the audio portion from an instantiation is digitized. For a digital audio signal, the sampling rate is measured in kilohertz and is an indicator of the perceived playback quality of the media item (the higher the sampling rate, the greater the fidelity).
- essenceTrackBitDepth – optional. The essenceTrackBitDepth element specifies how much data is sampled when information is digitized, encoded, or converted for an instantiation (specifically, audio, video, or image). Bit depth is measured in bits and generally implies an arbitrary perception of quality during playback of an instantiation (the higher the bit depth, the greater the fidelity).
- essenceTrackFrameSize – optional. The essenceTrackFrameSize element measures the width and height of the encoded video or image track. The frame size refers to the size of the encoded pixels and not the size of the displayed image. It may be expressed as combination of pixels measured horizontally vs. the number of pixels of image/resolution data stacked vertically (interlaced and progressive scan).
- essenceTrackAspectRatio – optional. The essenceTrackAspectRatio element indicates the ratio of horizontal to vertical proportions in the display of a static image or moving image.
- essenceTrackTimeStart – optional. The essenceTrackTimeStart element provides a time stamp for the beginning point of playback for a time-based essence track. It is likely that the content on a tape may begin an arbitrary amount of time after the beginning of the instantiation.
- essenceTrackDuration – optional. The essenceTrackDuration element provides a timestamp for the overall length or duration of a track. It represents the track playback time. Best practice is to use a timestamp format such as HH:MM:SS[:|;]FF or HH:MM:SS.mmm or S.mmm.
- essenceTrackLanguage – optional. The essenceTrackLanguage element identifies the primary language of the tracks’ audio or text. Languages must be indicated using 3-letter codes standardized in ISO 639-2 or 639-3. If an instantiation includes more than one language, the element can be repeated. Alternately, both languages can be expressed in one element by separating two three-letter codes with a semicolon, i.e. eng;fre.
- essenceTrackAnnotation – optional. The essenceTrackAnnotation element can store any supplementary information about a track or the metadata used to describe it. It clarifies element values, terms, descriptors, and vocabularies that may not be otherwise sufficiently understood.
- essenceTrackExtension – optional. The essenceTrackExtension element is an extension element. Extensions are either a wrapper containing a specific element from another standard OR embedded xml containing the extension. The essenceTrackExtension element is a container to accomodate track-level metadata from external systems. Use it to supplement other metadata sub-elements of instantiationEssenceTrack in which it appears.
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