XA disc a promising new medium for authoring and distribution

This month, Kodak Corp. and Philips will release the data structures and the file format specifications for Kodak’s Photo CD product line, which is expected to hit the market in June 1992.

Photo CD, you will recall, is the new film scanning and recording system developed by Kodak that allows some 100 35mm photos to be “printed” and distributed on a writable compact disc and displayed on a TV screen.
The fact that Kodak has worked closely with Philips to make Photo CD compatible with Philips’s Compact Disc-Interactive (CD-I) specification has been well documented. But what’s less well understood is that Photo CD is actually a CD-ROM XA disc.

This means a Photo CD disc not only plays in a CD-I player, but is capable of carrying interleaved audio, text and image data, as well as Photo CD picture data, to be accessed by a personal computer.

SOUNDS LIKE A NEW TITLES MEDIUM

Thus, what started out as a new and interesting consumer technology not only may become a powerful means of publishing photographic images for use in computer-based applications, but is very likely to become a new medium for creating and distributing multimedia presentations. In fact, it may even prove to be a powerful incentive for people to buy CD-ROM XA drives or upgrade their old CD-ROMS.

A bridge format. CD-ROM XA is an addendum to the Yellow Book, which details the physical formatting of CD-ROM discs. When the XA specification is used to lay data onto an optical disc, it allows audio, text and image data to be interleaved within tracks or sectors on a compact disc. Photo CD uses a bridge format that allows CD-ROM XA drives and CD-I players to read data from the same disc.

(A standard Yellow Book CD-ROM does not allow for interleaved data, so today’s CD-ROM drives cannot take advantage of the enhanced capabilities of CD-ROM XA. To do so, the user needs to have an XA-compatible drive.)

Writable CD. The Orange Book specification, developed and licensed by Sony and Philips, is what’s used to create these XA- and CD-I compatible discs. Using some formidable technological tricks, it allows developers to lay down digital data streams on a writable optical disc (sometimes known as “write-once”) — not a standard, prestamped compact disc — in such a way that the disc acts just like a standard XA or CD-I disc.

This is no mean feat. Standard optical discs can only be manufactured by a special mastering process that permanently encodes the data by stamping pits into the surface of the disc. Data is read by a laser that notes the transitions from a non-pitted area to a pitted one.

Writable discs are fundamentally different. They contain what’s called an “active layer” of dye, which absorbs laser light to change the reflectivity of the disc’s surface instead of changing the physical surface of the disc itself.

The technical win. Write-once technology makes it possible to write discs on-site, one disc at a time, instead of sending them off to be mastered and mass-produced. Until the Orange Book was written, the only way to read a writable disc was to both create it and play it on an expensive system designed specifically for that purpose.

The technical win with Orange Book was to make the laser’s reflections appear the same to the reader. In other words, they fool the laser into seeing the changes in reflectivity as actual physical surface variations, so that writable media can be read by equipment that was not designed to do so.

NOT JUST FOR CONSUMERS

Kodak is banking that the simple ability for consumers to “play” their 35mm photographs on their televisions, via its own Photo CD player, will be a mass consumer product in its own right. But as a result of Photo CD’s compatibility with CD-ROM XA and its compliance with the Orange Book standards, the company is positioned to make a significant impact in the digital media marketplace as well.

Conversion for CD-ROM XA users. Scott Brownstein, advanced development manager of Kodak’s CD Imaging Division, says all that’s necessary to make Photo CD operational in CD-ROM XA drives is some additional software, which Kodak is already developing. Although the software will certainly be available through retail channels, says Brownstein, the company is also considering bundling it with applications and/or CD-ROM XA hardware.

Kodak’s XA software development is following three tracks. One is an accessory that allows users to pull an image off a Photo CD and paste it into their existing applications (this was demonstrated on a Macintosh at the Seybold Computer Publishing conference earlier this month). Another is the creation of plug-in modules that allow Photo CD images to be imported into existing applications, such as Adobe’s Photoshop. The third, for independent software developers, is a toolkit that will enable vendors to include Photo CD as a new data type in upgraded versions of their applications.

Kodak is also experimenting with software that converts Photo CD images to dvi, the digital video format codeveloped by IBM and Intel. And since Kodak’s Photo CD photofinishing equipment is based on Sun Microsystems’ Sparcstation platform, a Unix accessory, module and toolkit are well under way.

CD-based presentations. Since Photo CD is XA-compatible, thus supporting interleaved audio and text, consumers will be able to add both titles and narration to the photos on their Photo CD discs. But Brownstein says he envisions a new class of applications where Photo CD is used to allow authoring real-time presentations delivered directly from compact disc.

There are two methods for putting various media types onto an XA disc such as Photo CD. One is to interleave them with the image data. This, Brownstein says, will likely be the method of choice for people working to create multimedia presentations.

The other method is to append them at the end of the disc, using a “pointer” system in Photo CD that tells the system to play a certain audio track, for example, with its related picture — the most likely method for consumers without XA drives, since interleaved audio isn’t supported by Kodak’s stand-alone Photo CD player.

The nitty-gritty details of how people will actually accomplish this are not yet clear, but Brownstein says a customer will be able to take analog cassettes, as well as digital images, text and audio tracks stored on diskettes, to a Photo CD photofinisher. Tracks from audio CDs can be used as well (with the proper permission, of course).

WHAT ABOUT COPYRIGHT?

The potential success of Photo CD also raises the specter of millions of digital images being set loose on a public that has little respect for, or understanding of, copyright law. Though anyone who snaps a shutter owns the image he or she creates, the ability to easily copy these high-quality “digital negatives” onto hard discs, combined with the growing hunger for high-quality images in the multimedia world, begs for some kind of encoding scheme on a Photo CD disc that cites image ownership.

They already thought of it. Brownstein says the Photo CD specification includes the ability to record ASCII data about individual images — such as the source or author of the image — onto the disc. “We also have the ability to encrypt the print- resolution data so you can’t print out a copy of the photograph without permission of the owner,” he says. “Content providers and the photofinisher can play games with how high-resolution info is stored on the disc, so you can’t print without knowing what game they used.”

But the spec doesn’t include the ability to encrypt the lower-resolution data that Photo CD uses to display images on a computer screen –another situation rife for illegal copying, especially in multimedia applications and consumer titles. (Photo CD stores separate, resolution-based information for printing to paper, computer displays and television standards, HDTV, 1/4-screen and 1/16-screen thumbnails.)

Copyright information can still be included and displayed with each image, regardless of resolution, but there’s no way to prevent someone from using an illegally obtained image in a screen-based title.

“There will be intellectual property issues here,” says Brownstein. “You have to protect your own rights. But the other side is that if I can’t get my images to you in the first place, you won’t pay for them.”

The bottom line for business. Photo CD cannot really be considered expensive even for consumers. A Photo CD player that attaches to the TV is expected to cost less than $500, and the cost to “print” a roll of 35mm film onto a Photo CD disc will be around $16. However, anyone who really wants to exploit Photo CD’s capabilities for business presentations will have to buy a (comparatively) expensive CD-ROM XA drive.

But businesses have historically been willing to spend much more money to buy the tools they need, and given Photo CD’s potential, its success in the commercial world is likely to skyrocket.

Denise Caruso