Mastering CD-ROM

• Introduction to CD-ROM
• CD-ROM Input Specification
• CD-ROM Sectors & Modes
• CD-ROM Based Formats
• What do the different "books" mean?
• How much data can my CD-ROM contain?
• How do I make Hybrid MAC / PC ISO9660 disc?
• How do I make sure my CD-ROM is going to work?
• What about errors and glitches

Since compact discs store audio in a digital format they are suitable for storing other digital information. In 1984, Philips and Sony released the Compact Disc Read Only Memory (CD-ROM) specification, known as the Yellow Book. This defines the necessary additions to the Red Book for the storage of computer data.

The physical parameters of CD-ROMs are identical to those defined in the Red Book. The use of the data it contains is different. While audio CDs can be played at only one speed, CD-ROM drives exist with a range of speed options from normal (1x) to four times normal speed (4x) and, now, 12x. As the speed increases the access time decreases.

CD-ROM discs differ from CD audio discs in two important ways.

The data on a CD-ROM disc are divided into sectors which contain both user data and other data for control and (additional) error protection. The data on a CD-ROM are contained in files. All CD-ROMs therefore, need a file system to enable the computer to access the required file easily and quickly.

Generally, the user need not bother with the sector structure but should be aware of the file structure.

In order to use CD-ROMs you need to buy a CD-ROM drive (sometimes called a CD reader) and connect it to your computer. A CD-ROM has several advantages over other forms of data storage, and a few disadvantages. It can hold 700 megabytes (MB) of data, the equivalent of nearly 500 high-density floppy disks. The data on a CD-ROM can be accessed much more quickly than data on a tape, but CD-ROMs are considerably slower than hard discs. Like audio CDs you cannot write to a CD-ROM (but CD recordable discs do exist), so they are only used for prerecorded data. In addition CD-RW (Compact Disc Re-Writable) is now available, which enables you to re-record data on the CD.

CD-ROM Input Specification

We prefer CD-R masters for providing your content. The CD-ROM specification is defined in the Yellow Book which is based on the CD audio format but for computer data. The salient parameters are shown below:

 
You must use "Disk at Once Mode" when burning your data onto CD-R. Do not attempt to send us masters using "Track Incremental" or "burn session". Hewlett Packard and Sony burners are notorious for defaulting to this mode so be aware! Check with your software / hardware operational manuals for details. Disc at once mode finalizes the disc and prevents further additional data recording.

Storage capacity of our CD-ROMs:

682 Mbytes* of user data in CD-ROM mode 1 (2048 bytes/record) OR
up to 74:30 minutes of digital audio @44.1Khz OR
a combination of the above (enhanced CD).

* Note!! Technically a CD-ROM can hold just over 700MB of data or up to 80 minuets of music, but what happens is the track pitch (the space between adjacent tracks) gets compressed which can cause problems on certain players. CDman disclaims all liability on long playing CDs. Once you go over capacity (682MB , 74:30 min/sec) you are officially over red book and therefore your warranty is void against playback problems. CDman can replicate data found on any CD-R -so if you can fit the data onto a CD-R then you can glass it.

CD-ROM Sectors & Modes

Data stored on a CD-ROM disc are divided into sectors which are equivalent to the audio frames for a CD audio disc. At normal playback speed 75 sectors are read every second. For double speed CD-ROM drives this increases to 150 sectors per second and so on. Seek times, while the disc rotates to the required starting position, will also reduce as speeds increase.

Because CDs were designed primarily for audio, their use for computer data requires the addition of header data and error correction codes which are included in every sector. There are two different types of sectors defined in the CD-ROM specification, mode 1 and mode 2 (the latter being used for CD-ROM XA discs).

Mode 1 Sectors

Mode 1 sectors are intended for the storage of computer data. They are comprised of:

• Header which consists of Minutes, Seconds, Sectors (frames) and Mode (= 1).
• 2048 bytes of user data.
• Error detection and correction codes to give the CD- ROM data extra protection.
• While CD audio players are able to conceal errors that are not correctable which may result from a scratched disc, CD-ROM
  data (especially application code) needs to be error free.
• Mode 1 sectors are the simplest type and are used for most CD-ROM based formats which follow Yellow Book guidelines.
  

CD-ROM Based Formats

The first CD-ROM discs contained Mode 1 sectors designed for general computer storage on CD. Although not specifically designed for multimedia there are a number of important multimedia formats which use mode 1 CD-ROM as the basic method for storing data on CD.
 
 

How do I make sure my CD-ROM is going to work? - It is vital that you test your CD-ROM one-off master on as many different machines as possible. If you follow the formats listed in this section then you should have success. While we at CDman wish you the greatest satisfaction with your order, we cannot be held responsible for discs that fail due to improper pre-mastering.

A good suggestion is to load your CD-R master on a freshly formatted PC without any additional software or drivers. You can then test your program on a "common base" machine with the knowledge that missing drivers or utilities will result in an error, allowing you to add the drivers to the master or make adjustments.

All CD masters are scanned for 3rd party software to prevent anti-piracy.

What about errors and glitches - CDman digitally transfers your master and does not normally test for errors. If an error or glitch is found on your finished CDs we will reference your original master. If it is the fault of our glass master and not your master we will rerun your order free of charge. CDs will not be replaced unless returned COD to us. - No CDs may be returned without first obtaining an RMA number.