Optical disc recording modes
In optical disc authoring, there are multiple modes for recording, including Disc-At-Once, Track-At-Once, and Session-At-Once.
Disc-At-Once or DAO for CD-R media is a mode that masters the disc contents in one pass, rather than a track at a time as in Track At Once. DAO mode, unlike TAO mode, allows any amount of audio data (or no data at all) to be written in the "pre-gaps" between tracks.
One use of this technique, for example, is to burn track introductions to be played before each track starts. A CD player will generally display a negative time offset counting up to the next track when such pre-gap introductions play. Pre-gap audio before the first track of the CD makes it possible to burn an unnumbered, "hidden" audio track. This track can only be accessed by "rewinding" from the start of the first track, backwards into the pre-gap audio.
DAO recording is also the only way to write data to the unused R-W sub-channels. This allows for extended graphic and text features on an audio CD such as CD+G and CD-Text. It is also the only way to write audio files that link together seamlessly with no gaps, a technique often used in progressive rock, trance and other music genres.
Track-At-Once or TAO is a recording mode where the recording laser stops after each track is finished and two run-out blocks are written. One link block and four run-in blocks are written when the next track is recorded. TAO discs can have both data and audio at the same time.
There are 2 TAO writing modes
- Mode 1
- Mode 2 XA
DVD-R Disc At Once
Disc At Once recording for DVD-R media is a mode in which all data is written sequentially to the disc in one uninterrupted recording session. The on-disk contents result in a lead-in area, followed by the data, and closed by a lead-out area. The data is addressable in sectors of 2048 bytes each, with the first sector address being zero. There are no run-out blocks as in CD-R disc-at-once.
Session At Once
Session at Once or SAO recording allows multiple sessions to be recorded and finalized on a single disc. The resulting disc can be read by computer drives, but sessions after the first are generally not readable by CD Audio equipment.
Audio Master Quality Recording
Audio Master Quality Recording was introduced by Yamaha's in 2002. This recording mode significantly reducing jitter levels causing noise and clicks (-30% according to Yamaha) and improving audio and music recording quality to a level rivaling professionally prepared music CDs. It delivers clarity in the high and medium frequencies range, full bass reproduction and convincing spatial presentation, compared with a standard recording mode.
It uses a Disc At Once method, at 1x for best result but some recorders allow 4x and 8x speed mode as well. Since the pits and lands are longer, the quantity of information that can fit on a disc is less than with a normal method: 63 minutes instead of 74 minutes on a 650MB CD or 68 min instead 80 minutes on a 700MB CD. This enhanced durability can extend the life of a CD-R disc.
The main advantage of this recording mode are:
- an easier to read audio CD with an extended life
- reduced jittering levels
- improved stereoscopy and playback quality on low and high frequencies