Making Music
  Computer Music Software and Hardware

 Quick Guide To Audio CDs

There's more to creating an audio CD than simply clicking the Copy button. We slip in a few discs and go for the burn...

Creating an audio CD can be as simple or as involved as you want to make it. With most CD-R software you drag audio files into a playlist, click the burn button, go have a cup of coffee and come back to an audio CD. And that's fine. However, there's more to creating an audio CD than that.

Brought to Book

When the CD format was being developed, it was seen as the answer to many problems involving data storage, each with their own requirements. Consequently, there emerged a rather long list of CD formats named 'Books' to cater for each requirement.

This is a much-abridged and précis'd list:

	Red. This is the standard audio CD, recorded at 44.1kHz and 16-bit resolution.
	Yellow. A general format for storing computer data and for multimedia use for playing audio and video from the CD.
	Blue. Enhanced CD, also known as CD Extra, comprising audio and data sections allowing the CD to be played by an audio player and in a computer.
	White. Essentially Video CD.
	Orange. Defines the recordable CD format comprising CD-R, CD-RW and CD-MO with multisession capability.

The main Book of interest to musicians is the Red Book. Although other formats can be created by general purpose CD-R software, you really need dedicated audio CD software to take advantage of the special audio CD features.

If you want to produce a 'normal' audio CD without any frills, then the utility that came with your CD-R drive will probably do the job.

The two most popular bundled pieces of software are Adaptec's Easy CD Creator and Ahead's Nero and these are very easy to use, essentially requiring little more than dragging audio files and dropping them into a playlist.

All at once

There are two ways a CD can be burned - disc at once (DAO) and track at once (TAO). As the names suggest, DAO burns the entire disc in once go whereas with TAO the disc is burned a track at a time.

The problem with TAO is that the process records two run-out blocks at the end of a track, and a link block and four run-in blocks at the start of the next track. These are just 'housekeeping' data but they can confuse some dedicated audio CD players which may click as they try to play them. CD ROM drives don't have this problem as they don't read between the tracks.

Tech terms Run-in/Run-out blocks Small pieces of data written at the start and end of each track when using TAO mode writing. Frame The smallest unit of data a CD drive can access, comprising 24 data bytes, subcode and error correction. CD-R CD-Recordable. Can only be written to once. CD-RW CD-ReWritable, able to be written to and erased many times.

In addition, features such as changing the gap between tracks require DAO writing.

The bottom line is simply to use only DAO when creating audio CDs. This is not a problem with modern CD-R drives but some older drives may not support DAO writing.

Good sessions

When CDs were first launched, one heavily-promoted advantage was their massive storage capacity. However, not many people created 650Mb of data in one go so multisession writing was devised allowing you to fill up a CD bit by bit by writing to it in several sessions. This multisession capability was probably most used with photo CDs when people were encouraged to put their photos on CD in several goes and then take them along to the chemist for printing.

A CD-R must be multisession-compatible in order to read a multisession CD - all modern ones are - but, again, this is not recommended for creating audio CDs.

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