Track-at-once

Track-At-Once ( TAO ) is the name of a CD recording process in which all tracks are individually written to a CD-R . TAO therefore allows a CD-R to be written to in several passes. Since the error correction of the sectors on the CD extends over the neighboring sectors, with TAO an illegible zone arises between the individual tracks, which is required to set up the error correction again.

So that the burner can "catch up" with the error correction after the break, it writes run-out blocks after each saved track and run-in blocks for each started track , which is noticeable on audio CDs by annoying crackling.

Compared to the Disc-At-Once (DAO) process, TAO enables the user to only partially fill the CD-R and only play the rest later. The disadvantage of this is that the pause between the tracks is at least about 93 ms (seven blocks) long, which is annoying with audio CDs; with many (older) burners it is even two seconds long. With TAO the minimum number of blocks of 300 must not be undercut, and a maximum of 99 tracks can be written per disc - both of which also apply to session or disc-at-once if the resulting CD is to conform to the standards.