Optical disc recording modes

Disc-At- Once ( DAO ) is a general term for a group of write methods by which an entire CD or DVD including lead-in and lead-out ( start and end ) is written without turning off the laser between or re- adjust. From the write methods mentioned in the MMC standard and RAW SAO fall into the group of the DAO methods of writing.

Advantages are that breaks or gaps ( " pregap ", index 0) can be set to values ​​between tracks that are not allowed in the standard. Not all drives allow the SAO mode setting the length of the index -0 to arbitrary values ​​. As in RAW mode, the drive does not evaluate what is burned, any index -0 length on all drives is possible to support the RAW mode.

RAW

When raw, Eng. for " unprocessed ", " raw ", is without specifications of a CD, respectively. DVD format worked. Such a CD is added in portions, for example, written as a memory dump to a file or written to disk from this from a dump file, evaluate or without changing the format of the data in RAW mode.

RAW is the only write mode, with which it is possible subchannel RW, CD Text and ISRC information, catalog numbers, CD MIDI, gaps, indices and manipulated TOCs to write. There are three different modes RAW:

  • RAW writes 16 P -Q (16 bytes) subchannel. 2 bytes of CRC data in the Q-channel are generated by the burner.
  • RAW 96P writes PW ( 96 bytes ) subchannel, but 2-byte CRC data in the Q- channel are generated by the burner. This mode is often used in practice, and is supported by a few burners.
  • RAW 96R writes P -W ( 96 bytes ) subchannel. This is the best mode and allows to write all subchannel information.

These additional data of the subchannel are for advanced features such as CD- text, but also for copy protection mechanisms relevant. Paradoxically, it is possible in these modes the burner to write data that he can not read; formats like CD-Text or CD G may be duplicated, even if the recorder does not support it basically. But this, the data must have been previously read correctly, for example using a different drive.

In RAW mode can theoretically a multi-session CD are described in a train. However, since no RAW mode support burning program is known, this can be a PMA write in RAW mode, such discs can not be continued and be recognized by Philips burners even as a defect and unreadable.

SAO

The Session -At- Once mode ( SAO), the data is also written to the media without turning off the laser, but a so-called B0 pointer can be set and the drive writes in this case (but with a write interrupt ) an additional PMA before the lead-in. Thus, additional sessions may be added. This is used eg in CD-Extra.

Swell

  • Discussion of DAO and SAO ( version 25 February 2009 at the Internet Archive )
  • Multimedia
  • CD
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