IASA-TC 06 video guideline: video "payload"

This is the fourth of a series of five blogs on IASA-TC 06 by the guideline's coordinating editor Carl Fleischhauer.

The preceding blog in this series reported that the authors of IASA's new Guidelines for the Preservation of Video Recordings, IASA-TC 06, struggled with the question of which digital target formats to recommend.  For now, multiple options are identified, framed by four principles that guide format selection.  This list of principles raised its own problems, however.  The authors report that one of them is - at this time - imperfectly realized in most existing digitization operations, format type notwithstanding.

The imperfectly realized principle is produce a complete and authentic copy.  What makes this tricky?  It requires archivists to consider and appraise the entire video payload, i.e., not just picture and sound essences, to identify elements that ought to be retained, generally elements that are "in" the source video recording in one form or another, many categorised as ancillary data.  Once the appraisal identifies "keeper" elements, digitisation systems must be capable of extracting, documenting, and storing those payload elements.  The authors recognize that only some originals carry all of the legacy-payload elements listed, while others carry only some (or none) of these elements.  In addition, depending upon the particulars, the appraisal may conclude that a given archive need not retain a given element from the source video.

IASA-TC 06 describes several of these payload elements together with associated instructions.  This blog divides the elements into three groups, the first of which pertains to time code.  In this case, the mandate for an authentic and complete copy - if confirmed by the appraisal - calls for the existing time code data to be retained, to support "forensic" research by future researchers, not playback per se.  Legacy time codes are often discontinuous and may lack integrity and, for this reason, IASA-TC 06 recommends that - in addition - a fresh, continuous, high-integrity master time code be recorded into the digitised copy to support playback.

  • Time code: retain legacy time code(s)
  • Time code: provide coherent master time code
  • Time code: label multiple time codes    

The second group includes other types of ancillary data.  Their extraction and digitising may entail re-encoding the elements and adding metadata just as the digitisation of picture and sound essences requires re-encoding and the addition of metadata.  

  • Captions and subtitles: retain and carry captions and subtitles, convert to XML Timed Text if possible
  • Audio track layout and labelling
  • Language tagging: provide a means to tag Timed Text languages
  • Language tagging: retain language tagging associated with binary caption or subtitle data
  • Language tagging: provide a means to tag soundtrack languages

The third group consists of elements that do not pre-exist - call them payload-to-be - but they represent valuable added data that ought to be created as a part of the digitisation process.  In the following bulleted list, the controlling verb is embed, as though the data must be carried by the new digital file.  However, the authors recognize that some archives will prefer to capture and maintain segments of this data (and indeed certain of the ancillary examples above) in collection-management databases, sidecar files, and the like.  That is: they will keep the data but will not embed it in the master file.  This topic receives additional discussion in IASA-TC 06.

  • Embed frame-level fixity (content integrity) data
  • Embed text-based and binary data: provide carriage of supplementary metadata (text-based data, e.g., process or preservation metadata like PREMIS)
  • Embed text-based and binary data: provide carriage of a manifest (text-based data)
  • Embed text-based and binary data: provide carriage of EBU STL, still images, documents, etc. (binary data)

Alas, the imperfect realization of complete and authentic copies includes those currently produced by the archives that are home base for some IASA-TC 06 authors.  To a degree, what is written in IASA-TC 06 is aspirational.  The authors are convinced of the value of these payload elements for long-term preservation—there is more on their value in the guideline proper—and the listing is partly intended to heighten awareness of this topic and to encourage the continued development of practices and tools.

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