Datastreams
- MM Hanke
User-provided
OBJ
REQUIRED
Primary media file (e.g. image, audio or video). The media file stored in the OBJ datastream is conventionally a production or publication file. The OBJ datastream is the source of any derivative made available for publication via the Collections portal.
The OBJ datastream for an asset should contain a publication/production file. Curators can decide which processing steps should be applied to an archival file to create a publication copy (for instance cropping, stitching or certain color corrections of images). Curators can also decide to use a publication copy that is virtually identical to the archival file. In any case, curators should consider that the OBJ datastream is currently the only source for media content to be published to the Collections portal.
Paged content/complex assets, publication type assets or collections do not have an OBJ datastream.
MODS
REQUIRED
Descriptive metadata about the asset, organized according to the Metadata Object Description Standard (MODS).
ARCHIVAL_FILE
OPTIONAL
OCR_CUSTOM, FULL_TEXT_CUSTOM
OPTIONAL
User-generated full-text, e.g. as the result of optical character recognition (OCR).
The PDF datastream is system-generated for page assets that are part of a book or serial issue. If you provide a PDF datastream for a page-level asset, it will be overwritten when the creation of a PDF for the book or serial issue is triggered through the DAMS GUI.
Derivative of the content represented by the asset in PDF format.
Typically provided by Digitization Services for assets which comprise multiple pages (paged content).
TRANSCRIPT
REQUIRED for Audio content
Textual representation of linguistic content in audio and video assets. Required for audio assets to be publishable. Optional for video assets.
Transcripts MUST be in plain text.
CAPTIONS
REQUIRED for Video content
Timed textual representation of linguistic content in audio and video assets. Required for video assets to be publishable.
Captions MUST be provided in WebVTT format.
PROXY_MP4
Audio content can be provided as streaming media, which adds a limited technical hurdle against a simple download of a complete MP3 audio file. If you prefer to deliver audio content as streaming media, you need to externally create an MP4 derivative and ingest it into a datastream labeled PROXY_MP4. Please submit a DAMS support ticket for details on this step.
If you are familiar with using FFmpeg for transcoding, we recommend using the following parameters for creating a PROXY_MP4 datastream: -acodec aac -ar 44100
Invoking ffmpeg with these parameters should result in AAC files using the AAC-LE profile, with 44,100 Hz sampling frequency (CD Audio standard).
See Manipulating A/V files with FFmpeg for a guide on how to use FFmpeg to convert/transcode audio and video files.
System-generated
Depending on the ingest method (manual or batch) and the type of content that is ingested to the DAMS (see Content models), the DAMS will automatically create some datastreams.
The system-generated datastreams serve pre-defined functions in the DAMS and are managed by the system. If you want to add a custom datastream, do not use one of these IDs, otherwise the system might overwrite custom data.
RELS-EXT
DAMS-specific metadata about the sub-collection an asset belongs to and about access permissions.
TECHMD
Technical metadata about the content of an asset's OBJ datastream, e.g. information about file format, compression algorithms, creation and modification dates.
POLICY
Metadata about the role-based access permissions to an asset inside the DAMS.
DC
Descriptive metadata about the asset in Dublin Core format, automatically derived from the MODS metadata provided by the user during ingest.
TN
Derivative image file: Thumbnail image.
JPG
Derivative image file: low-resolution dissemination copy.
JP2
Derivative image file: JPEG 2000 copy with lossless compression, for use in the Collections portal.
PROXY_MP3
The PROXY_MP3 datastream is automatically generated upon ingest from an OBJ datastream that contains WAV (waveform audio) data. If you publish an asset with a PROXY_MP3 datastream to the collections portal, the file will be made available to the embedded player as a progressive download. Users can download the complete MP3 file with relative ease. Audio content can be provided as streaming media, which adds a limited technical hurdle against a simple download of the complete MP3 audio file. If you prefer to deliver audio content as streaming media, you need to externally create an MP4 derivative and ingest it into a datastream labeled PROXY_MP4. Please submit a DAMS support ticket for details on this step.
Derivative audio file with MPEG Audio Layer III encoding. Automatically generated upon ingest by the DAMS using lame, for use in the Collections portal.
lame is invoked with the following parameters: -V5 -vbr-new
The parameters used by the DAMS software for creating the PROXY_MP3 datastream cannot be configured. If you experience sound quality issues that might be due to the encoding, please submit a DAMS support ticket.
MP4
Derivative video file: MPEG-4 media container file, automatically generated upon ingest by the DAMS using ffmpeg with H.264 video encoding and AAC audio encoding (AAC-LC profile). Used in the Collections portal.
ffmpeg is invoked with the following parameters: -vcodec libx264 -preset medium -acodec aac -strict -2 -ab 128k -ac 2 -async 1 -movflags faststart
The parameters used by the DAMS software for creating the MP4 datastream cannot be configured. If you experience image or sound quality issues that might be due to the encoding, please submit a DAMS support ticket.
OCR, FULL_TEXT, HOCR
Full text generated by the DAMS during ingest or when OCR process is triggered in the DAMS GUI.
The PDF datastream is system-generated for Page assets that are part of a Book or Serial Issue. If you provide a PDF datastream for a Page-level asset, it will be overwritten when the creation of a PDF for the Book or Serial Issue is triggered through the DAMS GUI.
System-generated for Page assets when PDF creation is triggered through the DAMS GUI.
UTLDAMS_PDF
Derivative PDF container for paged content, generated through the DAMS GUI or upon ingest.
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