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What TAO/SAO/DAO/RAW DAO means?

#1
Before reading this post you must know that when you extract an image from a CD (useful in order to do a 'true copy' of the CD, whose layout is made up by 'sectors', 74 min = 330,000 sectors) you can extract data in many ways:
1) 'cooked' (2048 bytes/sector);
2) RAW (2352 bytes/sector)
3) RAW+SUB (2352 bytes + 96 bytes for subchannel data P-W = 2448 bytes)
SUB data are sometimes used for storing CD-TEXT, CD-G (Karaoke) and some protection methods.


Well, when you burn back the extracted info on a CD-R you can choose between 5 different burning modes (not all software supports them):

1) TAO (track-at-once).
You burn on the CD-R all data (2048 of 2352) but recalculate - thereby changing them - all correction codes. On multiple tracks CDs, the laser pauses between them (this mean you cannot record Live Audio CDs without gaps)

2) DAO/SAO (disc-at-once , session-at-once).
As TAO, but the laser does not pause between tracks. This way you will not add extra pauses between tracks. You can record Live Audio CDs without gaps.
(SAO is smilar to DAO, but DAO closes the disc, SAO closes only the last session)

3) RAW SAO (sometimes simply called 'RAW Write').
You burn all 2352 bytes you extrcatced on the CD. Since you do not recalculate ECC/EDC, you end up with an 1:1 copy of the sector. Please note that since the error correction codes are not recalculated, the chance of burning incorrect data is higher. Avoid burning at very high speed.

4) RAW SAO 16 (sometimes called DAO 16).
As RAW SAO, but you'll also write P and Q subchannel data (8 bytes each). You need an image complete with .SUB info to do that (CloneCD, for instance; .BIN/.CUE format is no good for that since olny stores the 2352 part). You'll end up with an 1.1 copy of the sector plus the P-Q subchannels.

5) RAW DAO (sometimes called DAO 96).
As above, but you'll also write P - W subchannel data. As above, you need an image complete with .SUB info to do that. You'll end up with a 'perfect' copy (1.1 copy of the sector plus the P-W subchannels).

For backup purposes of many protected CDs RAW DAO is suggested.
If your burner does not support RAW DAO you might try these minimal settings (to be confirmed yet):
- Safedisc and Laserlock backups NEED at least RAW SAO (Safedisc v.2 backup needs also FantomCD/Alcohol's 'Bypass EFM errors' or CloneCD's 'Amplify Weak Sectors' settings)
- SecuROM and Libcrypt (PSX) NEED at least RAW SAO 16.
This message has been edited since its posting. Latest edit was made on 18 Feb 2003 @ 1:25
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