Packet Written Discs as Masters
Most CDR's are written in a "Track-at-Once" method where an entire track is written with one burst of the laser. "Packet" writing is a method where several write events are allowed within a track and reducing overhead.
This packet format is often presented to the user by "giving the CDR drive a letter" so that it looks like a hard drive that files can be dragged to from the desktop. Usually files can also be deleted from the disc but unless the disc is a CDRW, the space that was occupied is lost. This makes it very easy for the user to create the CD but it does come at a price. Packet software uses a new standard file system called UDF (Universal Disk Format), far more complex than ISO 9660, the file system found on 'normal' data CDs.
The discs that are created this way cannot be easily duplicated or replicated. (for a definition of the difference between duplication & replication). The reason for this is simple. Before any data can be packet written, the disc is first "formatted" by the DirectCD® program. This format actually creates an artificial header on the disc that, in effect, points to data that will be there later. Other computers that have the DirectCD® driver can read these discs but replication plants and CD-ROM service bureaus can't make exact duplicates of these discs because the actual data on the disc does not match the header. The duplication equipment attempts to read data that isn't there and fails. The only way to duplicate a disc written in this manner is to copy the files off onto a hard drive and then re-master the disc into a standard format.
What does all this mean to you? Don't send your service bureau a packet written disc to make copies. They will either ask you to send an new CDR master or they will charge you to do it for you and send a copy for your approval, costing you both time and money.
by Jon Beckmann
Service Bureau Manager