Too Much Info about CDRRW

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Too Much Info about CD-R/RW

• A dramatic rendition by Bob Sulecki
• 18 February 2002

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What is the difference?

• CD-R Compact Disc Recordable, a write-once
  technology. One mistake and youve got a coaster
• CD-RW Compact Disc Rewritable, can write and
  erase many times. Theoretically, a CD-RW disc
  can be re-recorded 1000 times, some manufacturers
  claim the number is closer to 100,000

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CD-R, quick growth affordable
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CD-RW speed format

• Example 32 x 10 x 40
• 32 x write
• 10 x rewrite
• 40 x read
• base speed is 150 KB/s

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CD Recording Methods

• Disc-at-once
• Track-at-once

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Disc-at-Once

• Data written continuously until entire data set
  is written
• Advantage eliminates linking, run-in, and
  run-out blocks
• Disadvantage have to have all data ready now

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Track-at-once

• Allows a session to be written in a number of
  discrete events (tracks)
• Advantage can keep adding events until cd is
  used up
• Disadvantage each track has 150 blocks of
  overhead for run-in, run-out, and linking
• max. of 99 tracks per disc, track length min of
  300 blocks (1 block 2KB)

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Packet Write

• Several write events are allowed within a track
• Advantage less overhead. Where one track had
  150 blocks of overhead, one packet has only 7
  blocks reserved for overhead

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Sessions

• Multi-session
• Open Session
• Closed Session

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Multi-Session

• Can be complete by itself
• Have the option of adding to later
• Problem sometimes only first or last session
  recognized

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Open Session

• Session not complete
• can add to later
• must finalize to make session complete

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Closed Session

• Session is complete
• any session that has been fixated
• fixation vs. finalization

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Fixation vs. Finalization

• Fixation-- writes the sessions lead-in and
  lead-out information. Closes a session, it is
  required before a cd can be used by cd-rom or
  audio player
• Finalization-- absolute lead-in/lead-out written,
  drive told not to look for subsequent sessions.
  No more information can be added to disc

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Burning a CD-R

• Reflective layer usually silvery alloy or 24-K
  gold
• Recording layer is dye
• WORM (Write Once, Read Many)

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CD-R burning

• Laser heats up to critical temperature

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CD-R burning

• Laser heats up to critical temperature
• Burns pits into organic dye in pre-formed grooves

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CD-R burning

• Laser heats up to critical temperature
• Burns pits into organic dye in pre-formed grooves
• Burned area becomes opaque due to chemical
  reaction with heat

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CD-R burning

• Laser heats up to critical temperature
• Burns pits into organic dye in pre-formed grooves
• Burned area becomes opaque due to chemical
  reaction with heat
• Mimics the way light reflects off pits and lands
  on conventional cd

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CD-R care

• Dyes in CD-Rs sensitive to UV light
• Keep in protective case like standard cds
• Results of mathematical models show the
  information will last 70-200 years

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CD-RW burning

• Crystalline compound replaces dye in recording
  layer of cd-r
• Two dielectric layers to draw excess heat

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CD-RW burning

• Crystalline compound a mix of silver, indium,
  antimony, and tellurium
• phase change technique
• When compound heated then cooled, it becomes
  crystalline (good reflector)
• Heated to higher temperature then cooled, becomes
  amorphous (bad reflector)

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3 laser powers

• Write power (highest) creates amorphous state on
  recording layer

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3 laser powers

• Write power (highest) creates amorphous state on
  recording layer
• Erase power (middle) melts the recording layer
  and converts it to a reflective crystalline state

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3 laser powers

• Write power (highest) creates amorphous state on
  recording layer
• Erase power (middle) melts the recording layer
  and converts it to a reflective crystalline state
• Read power (lowest) does not alter the recording
  layer, used for reading data

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StandardsISO-9660

• ISO 9660- covered recordable media
• Was adopted in 1984
• Set 99 track limit, specifies that data starts at
  track time 000216
• Inappropriate for DVD and CD-RW

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UDF

• Universal Disk Format replaced ISO-9660 in late
  1990s
• Compatible with DVD and CD-RW, and will be
  revised to cover any future formats of discs
• Enabled packet writing

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Burnproof Technology

• Helps to counter buffer underrun
• When buffer falls below threshold, laser turned
  off
• Recording picked back up in same spot when buffer
  full again

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Any questions?

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References

• The textbook (of course!)
• www.cdrfaq.org
• www.pctechguide.com/09cdr-rw.htm
• www.pcguide.com
• www.nswc.navy.mil/cosip/nov97/cots1197-2.shtml