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

• 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