NDSA:Standards and Best Practices Working Group/Optical MeetingNotes/Duryee: Difference between revisions

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  • Alex Duryee (AudioVisual Preservation Solutions) @archivetype
    • Article, meant to be intro to optical disc preservation: http://www.avpreserve.com/wp-content/uploads/2014/04/OpticalMediaPreservation.pdf
    • Research being done by colleagues - studying preservation of physical media but little information exists about the process of extraction and logical structure of what is on a disc.
    • What is on this disc? How to view and assess? There is no go-to process for examining.
    • Precedent is law enforcement - however, few criminals use CDs and optical discs so often not supported by forensics tools.
    • 92% migration failure rate for data extraction.
    • Researching discs as carriers of data.
    • Two major types of discs - audio and data
    • Audio: one of first uses of consumer optical media - designed to replace 8 track
    • Instead of filesystem paradigm these discs featured a single stream of modulated data running uninterrupted throughout the disc, with byte level metadata, such as track names.
    • Audio CDs more akin to tapes and vinyl because of this uninterrupted stream - only metadata differentiates “pieces” on the CD.
    • The human ear is bad at detecting small errors - CD audio standard is 44.1khz - 16 bit depth.
    • Even the best consumer/ professional hardware has a 98-99% accuracy in a given read - not good for preservation, as don’t know if you’re getting what you need - is it capturing important metadata?
    • CD-ROM/ data CDs - ISO 9660 - Similar to audio discs except broken to sessions and tracks
    • See it in a file browser and directories - convenient for archivists, what you see is what you get.
    • Data cds can contain multiple filesystems - older, early mid-90s HFS file systems were common.
    • Can contain all 3 filesystems and operating system used to extract data will default to one it can read. So: sometimes the OS can’t see the filesystem.
    • UDF filesystem started being used, manufacturers getting together to consistently use this filesystem.
    • ISO Buster - tool for this filesystem breakdown.
    • Other projects
      • Cabrinety Collection
      • WNYC - Audio disc project