Burning Multisession CDs with IMAPI2 in WSH
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In my last article, I showed you how you can use the Microsoft’s Image Mastering API (IMAPI2) control to create and burn single session CDs from a directory of files. Today, we’re going to take another look at the IMAPI2 control to create multisession CDs.
Traditional CD formats such as audio CDs and standard data CDs (like photo CDs, for example) are single session discs. In other words, all of the information on the CD is written to the CD at one time in a single burning session. Once completed, the disc is closed and its contents cannot be changed.
With the evolution of CD-Rewritable technology, things changed a bit. Because you were now able to write and rewrite to the same disc, support was added that allowed a person to write to the same disc again in a new session, thus appending data to a disc that had already been written. In other words, you could write data to the same disc across multiple sessions.
Of course, you would need a supporting drive to write the disc and you would also need a supporting drive to read it again. However, almost all CD-RW capable drives are capable of reading and writing multisession discs. That means that virtually every device currently on the market is capable.
In order to burn a multisession disc, each session must write its own lead-in and lead-out section on the disc. The first session will require around 20MB of space to accomplish this and each subsequent session will need a little over 4MB or so. This makes multisession discs slightly less efficient than single session.
This additional space is used to write information about the session, such as where the data starts, and how it fits into the disc's existing file system. The lead-in section of the first session is slightly larger than the rest because it includes a Table Of Contents. This TOC can be compared to a partition table on a hard drive. It tells the CD-ROM what type of file system is in use and where the data resides on the disc.
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