I've seen many conflicting answers online so:

When reading an optical disk, which one of these is true:

A 'pit' represents 1 and a 'land' represents 0


A 'pit' represents 0 and a 'land' represents 1

  • \$\begingroup\$ Either works - this would be a property of a particular specification \$\endgroup\$ – Chris Stratton Apr 14 '19 at 16:49

C. None of the above.

From Wikipedia:

The frames of channel data are finally written to disc physically in the form of pits and lands, with each pit or land representing a series of zeroes, and with the transition points—the edge of each pit—representing 1.

A change from pit to land (or land to pit) is a 1.

Consecutive pits (or consecutive lands) is a 0.

  • \$\begingroup\$ This is specific to CDDA; is it also the encoding used for data CDs? what about DVDs or BDs? \$\endgroup\$ – Hearth Apr 14 '19 at 19:46
  • \$\begingroup\$ @Hearth: As far as I know, all optical media use a similar scheme. \$\endgroup\$ – JRE Apr 14 '19 at 19:48
  • \$\begingroup\$ That would be a good addition to the answer, I think. Though... Even the weird ones like flopticals and laserdisc? \$\endgroup\$ – Hearth Apr 14 '19 at 20:09
  • \$\begingroup\$ Hmmmpf. "Laserdiscs" were analog. "Flopticals" stored the data magnetically and only used the optics to follow the tracks. \$\endgroup\$ – JRE Apr 14 '19 at 20:18

There's no yes/no answer. The usual optical disk data representation is NOT in one-to-one correspondence with the data recorded, rather a CD (for instance) eight-bit chunk of input is translated into a fourteen-bit group, and that fourteen-bit group is burned onto the disk. What convention you use for the fourteen-bit group is irrelevant to the user (who only gets the eight-bit decoded data back).

So, a single bit of input/output data doesn't correspond to a single feature on the disk in any one-to-one correspondence.


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