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Compatibility Bitsettings / Book Type Field
For a DVD player or drive to identify what kind of disc is loaded, it queries the so called "Book Type Field" found in the lead-in section of each DVD disc. These few bits, commonly referred to as "compatibility bitsettings" tell the drive which low-level format specification does the media conform to, such as DVD-ROM, DVD+R or DVD+RW.

Most DVD players will read a DVD+RW or DVD+R disc without any problems, however a small minority of them report a disc error when a disc is loaded that is not marked as a "DVD-ROM" disc in the compatibility bits. Ususally, these players are physically able to read the disc (since DVD+RW reflectivity is identical to that of a dual layered DVD-Video disc, which all players must be capable of reading), but their compatibility problems are due to different interpretations of these bits in the various firmware versions. In most cases, the problem can be solved by updating the firmware.

When a firmware fix is unavailable, or when you want to increase changes of playability when you give the disc to others with an unknown player, you could solve the issue by marking the DVD+R or DVD+RW disc as a DVD-ROM disc. This is what's called "changing the compatibility bitsettings". To instruct your DVD recorder to mark your DVD+R or DVD+RW discs as DVD-ROM, a special procedure must be followed. On a DVD+RW video recorder, you need to press a number of keys on the remote control. With a DVD+RW PC drive, you'll need a special utility program to accomplish this.

Note: You only need to apply this special compatibility setting to a disc if you encounter reading problems with your DVD equipment. Players and drives that need the DVD-ROM setting for DVD+RW discs are marked with (cs) in the compatibility list. DVD+RW drive vendors advice you not to apply these setting unless you specifically need so in your situation, however we think that no DVD drive or player should encounter problems with a disc marked as "DVD-ROM", as this is the default value for read only discs too.

On a DVD+R/+RW video recorder you can only change the bitsettings on a DVD+RW disc, after it has been recorded. DVD+R discs are recorded with the DVD-ROM identification, for highest compatibility.

Using a DVD+R/+RW PC drive, you can change the bitsettings on a DVD+RW disc, both on an already recorded DVD+RW disc, as well as by setting the drive to automatically write the desired identification by default on future DVD+RW or DVD+R discs. Since there is no way to change the identification bitsettings on a finalized DVD+R disc (as it is a write once), you can only set the drive to the desired bitsettings for new or unfinalized DVD+R discs.