In computing, optical disc authoring, including CD authoring and DVD authoring, known often as burning, is the process of recording source material—video, audio or other data—onto an optical disc (compact disc or DVD).
Process
Creating an optical disc usually involves first creating a disk image with a full file system designed for the optical disc, and then actually burning the image to the disc. Many programs create the disk image and burn in one bundled application, such that end-users do not even know the distinction.
There are also packet-writing applications that do not require writing the entire disc at once, but allow writing parts at a time, allowing the disc to be used like a floppy.
There exist many optical disc authoring technologies for optimizing the authoring process and preventing errors. Discs whose burn failed are colloquially termed coasters since that is all they are good for.
Sessions
Data on an optical disc is laid out in sessions. Each session consists of a lead-in, containing the session's Table of Contents, the program area in which the individual tracks are located, and the lead-out.
The number of tracks is limited to 99 in a session. The specifications require at least one track in each session. The tracks are located in the program area of the session.
In multisession discs, the lead-in areas contain addresses of the subsequent sessions. The TOC written in the lead-in of the latest session is used to access the tracks.
TOC
The Table of Contents (TOC) is the area where the layout of the tracks on the disc is described. It is located in the lead-in area of the disc session. The TOC on discs is in principle similar to partition table on hard drives.
Nonstandard or corrupted TOC records are abused as a form of CD/DVD copy protection, in e.g. the key2Audio scheme.
Lead-In
The lead-in area of a CD session is the starting part of the disc. It contains the TOC for the session, and the address of the next available free part of the disc available for the start of the next session, unless the disc is closed and therefore no more sessions can be added, or the disc is not multisession.
Lead-Out
The lead-out area is the ending part of the CD session. When the session is closed, the lead-out area is written.
The first lead-out is 6750 sectors (about 13 megabytes) long, each subsequent lead-out is 2250 sectors (4 megabytes) long.
Tracks
A track is a consecutive set of sectors on the disc containing a block of data. One session may contain one or more tracks of the same or different types. There are several kinds of tracks: Audio tracks, Data tracks.
Hardware
Authoring is commonly done in software on computers with optical disc recorders. There are, however, stand-alone devices like personal video recorders which can also author and record discs.
Software
Use of optical disc recorders require optical disc authoring software, (sometimes called "burning applications" or "burner applications").
