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What 'virtual tape' image format is most suited for data preservation i.e. can store metadata like density and media type of original tape, presence of data past EOT marker, parity/ECC bits etc.?

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    Do you mean magnet tape in general, or audio cassettes specifically?
    – snips-n-snails
    May 29, 2016 at 22:18
  • Magnetic tape when used as a data storage device -- compact cassettes were also used this way (f.e. DEC TU60 DECassette drive).
    – sendmoreinfo
    May 30, 2016 at 7:01
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    I'm not sure what you're trying to do. DEC tape drives had a processor on the interface that handled these parameters. Are you trying to develop a black box that pretends to be a tape drive? Are you trying to create a data file structure that emulates the tape encoding? I take it this isn't about copying tapes to a modern medium as that wouldn't need to know about ECC etc.
    – Chenmunka ♦
    May 31, 2016 at 8:35
  • This is about archiving, esp. when the tape is the last surviving copy and may be unreadable with standard controller, so that saving raw bitstream is the last chance to recover the data.
    – sendmoreinfo
    May 31, 2016 at 18:06
  • A waveform, or a set of synchronized waveforms in case of a multi-track tape, might be your best option.
    – Leo B.
    Jun 13, 2017 at 18:29

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The 'virtual tape' (let's say .TAP files) format will strongly depend on the actual tapes you're trying to back-up.

For example, Commodore (64) only cares about tape signal crossing zero, so a tape "emulator" simply emits those signals at given intervals. Markers (EOT, ECC) and others are also encoded as the same signals. This format simply determines binary 0 or 1 using "spacing" between those zero points.

More advanced system may use edge detection (ideally for a square wave), where it might recognize rising and falling edge for a 0 or 1.

If you're trying to backup tapes from another platform it may entirely have different format (such as wave type, often sine or square, amplitude coding, signal modulation, multiple tracks etc).

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    And don't forget tapes for minicomputers like the PDP-8 used multiple tracks on a tape (and it wasn't a cassette tape).
    – dirkt
    Jun 1, 2016 at 9:53

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