Telecommunications and CD-ROM
- friends or foes?

By Erling Maartmann-Moe

CD is neat

CD-ROM is publishing

CD-ROM is cheap

Surprise: CD-ROM has relatively high bandwidth!

CD-ROM is multimedia

CD-ROM has no meter

CD-ROM is standardised

CD-ROM and  the consumer

CD-ROM has become  CD-RWM

CD-ROM and telecommunications
When CD-ROM was introduced in 1986, it was met with a deep scepticism from many groups within telecommunications and computing. I remember speaking to a conference in Norway in 1987 about our then pioneering first Nordic CD-ROM production, after the honoured guest at the conference, Philippe Kahn of Borland, had exclaimed: 'In five years CD-ROM will be dead!'

The arguments against CD-ROM have been many and various: 'Who has decided that 600 Mb is an appropriate upper limit for an electronic publication?'- 'A storage medium that the user cannot store anything on?' -'Too slow!'- 'It won't last forever!' (Who does?)

Still, five years after this conference - in 1992 - the estimated installed base of CD-ROM drives passed 3,000,000 world wide, and the number of available commercial titles passed 2,200. And it is really after 1992, with the evolvement of multimedia in computing, that CD-ROM really is taking off. Most PCs are now available in models with CD-ROM built-in. Software and documentation are often delivered free on CD-ROM, at extra cost on paper.

CD-ROM is established in the marketplace. In some senses it may be a competitor to telecommunications. Many on-line databases have CD-ROM competitors, catalogues and documentation that might have been available through networks are distributed on CD-ROM. When one of the guest editors asked me to write this article, I was encouraged to write about what telecommunications should offer to compete better with CD-ROM for such applications. To answer that, we need to know the CD-ROM.

So, what is a CD-ROM technically speaking? It is a round, flat piece of plastic, 120 mm in diameter, with a spiral track on one side that contains small bumps detectable with a laser and a mirror. These bumps are used to model bits, and according to the ISO 9660 - the standard that defines the CD-ROM characteristics - these bits are grouped together in sectors of 2336 bytes, of which usually 2048 are available to the user. Sectors are played at a speed of 75 per second, giving a data rate of 1.2 Mbit/s. ISO 9660 says a lot more than this; it defines file structure, error correction codes and so on, but the important thing is that this piece of plastic can carry a little over 600 Mb of data that can be retrieved in a little over an hour.

CD-ROM as a medium is physically identical to the audio CD that was introduced to the world market in 1984. The audio CD has been an unprecedented success in the consumer market. In fact, as far as I know only two products have wildly surpassed the (often very optimistic) prognoses made by American market research companies: The CD and the fax machine.

CD is neat

The CD was far better than the old LP in sound quality (though I know some persistent analogue freaks disagree with this), and initially the CD appealed to the high-end audio market of people with disposable incomes. But the massive success of the CD in the consumer market cannot be explained only by the audio quality, it is in my opinion due to another factor: Its neatness: It is lightweight, it is easy to treat, it looks good when you hold it up in the light, it is robust, and it is easy to use. These properties of the CD of course also apply to the CD-ROM.

CD-ROM is publishing

The initial scepticism to CD-ROM was in my opinion based on a misconception, or rather a lack of understanding of this new medium. Initially, CD-ROM was often referred to as an optical storage medium. This is not entirely untrue, but since the user could not save to CD-ROM (you can now!), this made the CD-ROM look like a strange animal.

From a user point of view, CD-ROM is not a storage medium, it is a publishing medium, and consequently useful only in such a context. For anyone distributing rather large volumes of fairly stable data to a number of users, CD-ROM should be considered as a platform.

Rather large may mean anything from 50 Mbytes to Gigabytes - a CD-ROM does not have to be full to be useful; on the other hand defining a volume consisting of several discs is no problem. Stable is also a relative question - some large financial databases are distributed with new versions on a bi-weekly basis to subscribers, but generally one would not publish extremely volatile data on CD-ROM. The number of users does not have to be large - if the information is of great value to a user group, it is possible to make a CD-ROM production viable and profitable with less than 100 customers.

CD-ROM can be used for purely distributional purposes - moving files - or used as a vehicle for fully self-contained applications like an encyclopaedia. But it is not a storage medium.

CD-ROM is cheap

CD-ROM as a tool for professionals has the unique advantage of piggy-backing on a consumer product - the CD itself. Who would have thought in 1980 that a device containing a laser, a servo, an advanced D/A-converter and a power supply would sell for USD100 upwards? The CD-ROM is a little more expensive than an ordinary CD player due to a more advanced controller, higher demands on data correctness and MTBF, and faster access times. But it now retails at USD300 upwards.

The manufacturing process for CD and CD-ROM is identical for the disc itself, with a little higher quality demands for the latter. If you buy a Michael Jackson CD you get three things: The textbook, the plastic case, and the CD itself. In large volumes, the CD may be the cheapest of these three in pure production costs. For CD-ROM productions, it is possible to get down to less than a dollar per disc. Not much for 600 Mbyte!

Surprise: CD-ROM has relatively high bandwidth!

I think that one of the important aspects of CD-ROM when discussed in a telecommunications context is its bandwidth. A CD-ROM transfers 1.2Mbit/s continuously to the desktop. That may not be impressive compared with a harddisk, and CD-ROM is often regarded as a slow medium. But compared to available long-distance networks it is rather strong, especially since the kind of applications and data stored on CD-ROM often also are available in on-line databases in some form. Compared to most public long-distance networks like X.25 and ISDN, the bandwidth of CD-ROM is far ahead. In fact, it is so high that sending a CD-ROM by overnight mail gives the same bandwidth as one B-channel in ISDN - transferring 600Mbytes in a perfect 64 kbit/s channel takes 21 hours! (See table 1.)

CD-ROM players have since the introduction considerably improved access and seek times, and lately also transfer times. Although in a strict sense violating the CD-ROM standard, the new players double or even quadruple the transfer rate of the CD-ROM by playing it back at a higher rotational speed, thereby achieving transfer rates of up to 600 kbytes/s or 4.8Mbit/s. This works well for file transfer and for tailored applications, but of course not for audio and video intended for playback at normal speed, in which case speed must be set to standard 150Mbyte/s.

CD-ROM is multimedia

Being 'born' in the audio community, it is not surprising that CD-ROM is well suited for multimedia applications. Multimedia mixes the traditional data types like numbers and characters with audio, video, animation and MIDI data. In traditional applications data are displayed by the application, while in multimedia data are played, that is - time is an inherent property of multimedia data.

The distinct feature of the CD-ROM medium (contrary to for example a hard-disk) of having a fixed data rate, turns out to be an advantage in a multimedia context: A sustained, continuous and predictable data rate is guaranteed. This feature that is so essential to continuous media like audio, video and other time-dependent data types, is built-in for CD-ROM, while other channels like packet-switched networks and time-shared environments do not guarantee such a property without specialised protocols.

The CD-ROM format also allows for interleaving of data, so that one or more audio streams can be mixed with data and for example a video stream within each sector. This property assures synchronisation between different media, and also allows for software control of switching for example between different languages in an application. CD-ROM is now frequently used as a carrier for digital video in the form of MPEG, QuickTime or Video for Windows, and video can be played back directly and continuously with multiple channels of synchronised sound.

CD-ROM has no meter

A CD-ROM is sold like a book - you pay for it when you get it - using it is free. Contrary to telecommunications systems, there is no running meter, no expenses for information use or net access during use. This may imply higher initial costs, but on the other hand free use. It can be regarded as a mere pricing question, but it has quite deep implications in how users interact with the information. Browsing and exploratory use of the CD-ROM is encouraged by this pricing, while users in a net with running costs will tend to do things as quickly and goal-oriented as possible.

CD-ROM is standardised

The standard describing the physical format of all CDs, and the audio CD characteristics are often referred to as 'The Red Book'. CD-ROM was originally defined in 'The Yellow Book' (also called the 'High Sierra' standard after the hotel where the meeting was held), but it was standardised as ISO 9660 with minor modifications.

What the ISO 9660 ensures is just a common directory and file format so that the data on a CD-ROM can be read by any operating system with an ISO 9660 driver. A CD does not have to be made according to the ISO standard - both Apple and DEC have made CD-ROMs using proprietary file systems.

The standard defining the interleaving properties, plus some standards for audio (other than audio CD) and graphics, is called CD-ROM-XA, where XA stands for extended architecture. This format has become quite important because it is the basis of the Kodak Photo CD.

CD-ROM and the consumer

Special variants of the ISO CD-ROM requiring additional, proprietary add-ons, have been developed by Philips (CD-I), Commodore (CDTV), Kodak (Photo CD), and Sony (Data Discman). They are all special machines designed to be multimedia publishing platforms. None of them have so far had significant success in the marketplace, at least not sufficient to set a de facto standard for multimedia publishing. New, more powerful RISC-based machines like 3DO may have the power to become such a platform. Combined with the MPEG standard for video becoming available as cheap hardware decoders, full motion video will be an option on these players.

We do not know yet who will be the winner in this market, but they all agree on one thing: CD-ROM is the 'paper' for multimedia publishing to the consumer market.

CD-ROM has become CD-RWM

Producing a CD-ROM in the late eighties was a rather tedious process: Files had to be prepared by the publisher, sent to a production house for formatting and pre-mastering on special equipment costing over USD100,000, then sent on videotape to a CD-factory for mastering. A process as complex as book publishing, and since a CD physically was stamped out in plastic in a print-like process, it really deserved the label read only.

Not so anymore - writeable CD-ROM drives cost less than USD5,000, formatting software often included, and a blank disc costs around USD30. A general user with an ordinary CD-ROM drive cannot alter the information, but production can be done in-house in small quantities.

For larger quantities it is still more cost-effective to have the disc stamped in a CD-factory, but an in-house written CD can be used as a master - just send it to the factory.

Kodak's Photo CD has also forced the CD standard to be changed so that information can be appended to a CD-ROM. The Photo CD is aimed at professional as well as amateur photographers, it can contain 100 very high-quality digital images, but customers are not expected to fill one CD immediately. One film may be 24 pictures, the next time the customer brings the CD and the new film, and the pictures are appended to the old Photo CD. Consequently, the standard had to allow for filling the unused space on a writeable CD, and this had to be reflected in the CD's directory structure. A multi-session CD-ROM drive is able to recognise such multiple generations of data appended.

In other words: CD-ROM is evolving. I would not be surprised if, in a few years, a new generation of CD-ROMs with 4 times the bandwidth and 2 times the playing time of the current CDs are on the market. These will be used for carrying MPEG-2 coded video of very high quality to the desktop and to the consumer.

CD-ROM and telecommunications

So, to restate the question from the editor - 'What should telecommunications offer to beat CD-ROM?' - the answer should now be obvious: Provide a service that offers at least 1.2Mbit/s continuous bandwidth access to a vast amount of multimedia information from the desktop in a neat and user-friendly way at almost no cost!

We know that telecommunications technology develop so fast that this may not be a very distant dream, technically speaking. B-ISDN and ATM, optical cables, new technologies for video transmission through telephone lines like Bell Atlantic's ADSL modem, infrastructures like the World Wide Web - they are powerful enough to make (at least the current) CD-ROM technology obsolete in the future. But this is not only a question of technology, the decisive factor will be availability, and above all: price.

What can telecommunications offer currently? It is not much quicker to log on to an on-line database, compared to installing a CD-ROM. By the way - CD-ROMs can also be shared within a local network. Bandwidth to the desktop within reasonable costs is limited to modem, X.25 or ISDN. That is a maximum of 128kbit/s, which is less than one tenth of the CD-ROM. The initial equipment costs are generally higher than for a CD-ROM drive.

Few of the current network technologies offered can be called neat, they are generally not very user friendly to install and use, compared to CD-ROM. ISDN may have the potential to become such a technology, but needs to mature in the marketplace.

Telecommunications has three big assets compared to CD-ROM: Choice, updateability, and the option of two-way communication. Choice, because a user can browse in a vast world of information at will (provided the information of interest is not in a database that requires elaborate payment/user-id/password-procedures), without ordering and waiting for the physical arrival of a CD-ROM disc. Internet World Wide Web is an excellent example of how this can be done.

Updateability is the primary asset of telecommunications and on-line databases - the information is potentially fully updated, actual, new, corrected and so on. This is of vital importance to some types of information like pricing of goods, stock exchange rates and telephone numbers that change frequently.

Two-way communication is the third asset, which has the potential of coupling users together, for example by immediate response to marketing information, news, notices, requests, and so on.

These three assets should be utilised fully by telecommunications - in my opinion not to beat the CD-ROM, which is here to stay and has its strong sides. Rather, telecommunications should acknowledge the CD-ROM as an efficient carrier of vast amounts of multimedia information to large user groups, and enhance this information with telecommunications services.

It is possible for a CD-ROM application to have net connection integrated for ordering products, request updates, ask for additional information and services, send responses and opinions on products, connect to help desks, user groups and so on. Such enhancements are needed by many CD-ROMs, and would make them better products for the customer.

In my opinion, rather than seeing CD-ROM as a competitor, telecommunications companies should boldly use CD-ROM and enhance it with services and functionality that only networks can offer.