'Enhanced CD' Production:

Enhanced CDs utilize audio in session one (the disc will play on regular players like cars, homes etc) and then a second session is added which will play on personal computers (adds video, bios, web links etc.) Enhanced CDs fall under the "CD-ROM" banner. Please obtain a price quote using CDROM for your product pricing.

Audio should be recorded on session ONE and the Multi-media portion on session TWO.

Mastering Enhanced CD

Enhanced CD utilizes a multi-session format, with the following disc geography:

Session 1: "Red Book" Audio

Session 2: "Yellow Book" CDROM-XA, mode 2. The Extra/Blue Book spec imposes a minimum file structure requirement within Session 2 in addition to any stand-alone multimedia applications.

Session 1: Creating Audio

The audio section of an Enhanced CD must be a "Disc At Once" session that is unfinished to allow the second data session to be written. Any of the premier audio mastering software like SonicStudio or Sadie are now capable of writing unfinished audio sessions. Even though the Enhanced CD audio initially gets created within SonicStudio™, we prefer to have a professional CD-R software like Adaptec's Jam write the unfinished audio to CD-R. Sonic can generate an audio image file (actually a SoundDesigner II file compatible with JAM) that includes all tracking, subcode, and ISRC data.

Some audiophiles and engineers may question the integrity and convenience of converting the audio into a computer file format before writing to CD. Bit for bit testing (see below) has proven that writing an unfinished Red Book audio session using JAM produces an identical copy of the Sonic master. The audio image file can be conveniently archived or transferred to any computer workstation without error or degradation.

Why Not To Use Digital Audio Extraction

We discourage the practice of Digital Audio Extraction, which so many inexpensive CD-R packages offer. This process captures the samples from an audio CD-R played on a CD-ROM drive and writes them via the SCSI bus to a computer audio file on a hard drive. Since you can't monitor the copying process, it's more or less an act of faith.

While copying computer files from a CD-ROM to a hard drive is generally a straight-forward, error free process, digital audio extraction is somewhat more daunting and less reliable. An audio CD has a larger sector size (2,352 Bytes) than CD-ROM (2,048 Bytes) which means the CPU has to work about 15% faster while also decoding the audio data. Unlike CD-ROM sectors, CD audio sectors have no headers, just Q Subcode information. When the laser searches the Q Subcode to find its previous location, there can be an error of +/- 5 CD frames! This must be compensated for by smart copying software which performs 'overlap reads' by collecting redundant audio samples and deleting the ones that have already been written to the hard drive. For this reason, Digital Audio Extraction is not a reliable linear process.

Aural Verification

Regardless of the method you use to write the audio of an Enhanced CD, you need to be assured that the transfer process did not compromise the audio. When comparing the source and copy programs aurally, be sure to audition them through the same CD player or D/A. This will minimize the varying jitter characteristics of different digital audio media (CD, DAT, HD) and transfer protocols (AES,SPDIF,Optical). Remember, a digital audio copy pretends to be nothing more than a list of numbers with a generic sampling rate. Regardless of all the hyped up "anti-jitter" boxes and cables that exist in mastering studios these days, the potential jitter characteristics of a replicated CD come down to the final playback during glass mastering.

Checking the Audio Samples

There is a bit for bit test you can perform on the source files and CD-R session. Load both "before" and "after" programs into a Sonic System with all input dither and DSP disabled. Then synchronize the two programs to the audio sample. Play all four channels through a stereo output mixer but with one of the stereo programs out of phase. If the files are identical, they cancel each other out. A Sony PCM-1630 video screen confirms zero output with a black screen. This is a must for Enhanced CD clients who are concerned about the integrity of their audio on a dual session disc.

Session 2: Enhanced CD

Once the first round of audio premastering is finished, you're ready for round two: adding the multimedia track. Hopefully you are spared the agonies of authoring the multimedia, and the artist or developer will let you know how much room is left for the Enhanced CD track. Here's a simple formula:

10MB x Total audio minutes minus 650MB = MB available for Session 2.

The multimedia developer hopefully provides Enhanced CD data on one of several currently popular storage formats (Zip, Jaz, CDR). Your job is to successfully format and write this data after the audio to a CD-R that the plant can successfully master. Most of the time, the release is for both Mac and PC, so you may have to create a Shared Hybrid session, which may consist of an HFS directory and an ISO 9660 directory with common files. Be vigilant about ISO 9660 naming restraints (8.3 characters) , since some may want their release to be compatible with Windows 3.1. Create the Enhanced session in CDROM-XA format or more specifically, CD-ROM Mode 2, Form 1. XA stands for "extended architecture" and is a variant of CD-ROM used for multi-session.

Take extra care to make the Enhanced section functionally efficient and appealing. This means defragmenting and optimizing the files on the CD-R for optimum performance. It also means enhancing the appearance of the project on the desktop: creating custom icons for both Mac and PC, creating Auto Start capability, and discreetly hiding or making invisible files and folders that the end user need not directly access.

More information on this subject can be seen from the public Apple Developer PDF archives:

Enhanced CD Fact Book Guide for Consumers & Developers

Enhanced CD Survival Guide

Cross Platform Issues for Developers