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Traditional techniques for migration

Traditional Video Migration

Problems with Videotape

The major reason video needs to be preserved is because it fails as a storage medium. The medium is said to have inherent vice.


Since the day the tape was manufactured, the binder used to hold the magnetic particles (pigment) began to degrade. The process is called Sticky Shed Syndrome. There is some fundamental research on this topic but most to the valuable information was proprietary and was thus destroyed when the manufacture's libraries were moved into the dumpster, as tape manufacturers were sold to larger concerns.


Videotape is both the linear record of the images being presented and also the storage medium. Because it is a storage medium that is in the process of becoming unrecoverable, emphasis is often placed on moving the content onto a new videotape in an attempt to "preserve" the character of the object.


However, migrating the linear analog content into a digital format removes the problem of the storage medium forever. This assumes one migrates the digital copy to a new HDD or digital data tape (LTO for example) when required. A digital copy is always perfect, from one to the next, because the process copies "code" rather than an analog electrical signal. The goodness of the analog to digital transfer process has many variables, but cables, VTRs, A-D cards and formats exist that allow the original to be migrated into the digital domain with greater bandwidth than the original.





Van Bogart CLIR Fig3

View of a section of generic video showing the cross-section and magnetic top layer; image was used with permission from "Magnetic Tape Storage and Handling, A Guide for Libraries and Archives" by Dr. John W.C. Van Bogart National Media Laboratory, June 1995 on the <> website.

Magnetic tape is projected to have an average life of about 30 years. This figure varies based on physical storage condition, and assumes average good conditions. Standard storage condition are 40%RH and 68-72°F (plus or minus 5-10 degrees or percent humidity).If the videotape had excessive use, or was stored in a humid (>45% RH) or hot (>78°F) location, even a hot car in the summer (120-150°F) for a few days, it will fail before its predicted lifetime.


The electronic video information on the magnetic tape will generally maintain its (magnetic) integrity as long as the magnetic layer on the tape remains intact, but there are limitations. The magnetic storage medium, therefore, influences the longevity of the video element.


The better its storage the longer the video element will "last" before it needs to be migrated to a different storage media. Traditionally, magnetic tape media has been migrated to new magnetic tape, commonly to a more modern videotape format. However, each analog to analog (videotape) migration introduces changes into the video image stream. Some changes can't be avoided, but many can.


The unwelcomed changes are

  • Excessive passes over the magnetic heads
  • Unnecessary surface cleaning
  • Noise reduction (excessive) during capture
  • Color saturation or desaturation (chroma adjustments) during capture
  • Conformation to "Broadcast Legal" criteria (compress or expand to 7.5 to 100 IRE; luma adjustments)
  • Time-based correction (TBC) errors which result in frame jitter or misalignment

Analog video is video waveform direct from a source that is laid onto the magnetic media -- videotape. The source can be (a) direct from a video-imaging tube in a video camera, (b) an RF feed from an antenna or cable or (c) analog outputs from a videotape recorder (VTR), either an analog or digital type (miniDV for example).


Cool or cold storage is the only method to prolong the lifetime of videotape, but the diminishing availability of playback equipment limits the effectiveness of this strategy. At best, cold storage will help you hold an aged videotape in its current state as you work through the ongoing process of migration.


Migrating to new videotape will bring a temporary new life to historic videotape, because the video will be on a new storage media, but it will be one more generation removed from the original. In addition, when the time come for its migration, historic video playback equipment will be even more difficult to find and refurbish.


The highest quality analog video format is Betacam SP. Migrating to this Best Analog Format using new videotape will turn the clock back on the historic artifact, but (a) it will be second generation analog (master) and (b) the new tape only has a lifetime of 30 years. Playback equipment for BetacamSP is now considered threatened. Fewer and fewer BetacamSP decks are turning up on eBay.



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