|
This is truly an exciting time to be involved in educational technology. With recent advances in this area, it is possible to introduce materials and concepts in the classroom that were previously unavailable, or required considerable expense in the form of field trips or arranging for visiting experts to provide tuition. One of the most exciting dimensions of this new technology is the use of CD-ROM data storage and retrieval for personal computers. This media, which can combine digital quality music and images along with operating software, opens up whole new vistas to the classroom teacher. It is the purpose of this paper:This paper is aimed at academics interested in multimedia applications, CD-ROM technology, CBI in music and musical memory and at administrators interested in forward planning in music technology.
- to discuss the advantages of CD-ROM technology in the classroom;
- to explain the differences between various CD-ROM formats;
- to introduce a typical CD-ROM implementation in the classroom, using the Apple Macintosh hardware platform;
- to discuss the advantages and disadvantages of such a system and;
- to demonstrate CD-ROM programs currently available for both general music and more specific musical education as well as evaluation techniques
One problem facing early users was the configuration of the CD-ROM drive with the computer. Often this required following a complex set of instructions to get the CD-ROM unit and the computer to communicate successfully, and could require a lengthy adjustment period where minor (or sometimes major) bugs were ironed out. The units available today for most personal microcomputers are quite different from early models, with nearly all of the intimidating adjustments, connections and cables being eliminated. Indeed, it is possible in many cases to purchase the CD-ROM unit built into the computer, completely eliminating the connection problem. Even with the external units, however, there are usually only two simple connections to be made - one to place the CD-ROM under the control of the CPU, and the other to take the audio signal from the unit to an appropriate sound reproduction device.
Where the CD-ROM unit exists as an external device, the control connection is either a SCSI (Small Computer Standard Interface) cable or DMA (Direct Memory Access) cable. These unique cables have the advantage of only fitting one type of terminal, thus it is virtually impossible for even the most inexperienced operator to make an incorrect connection. Occasionally an external unit will need a small terminator plug, but the documentation will be quite clear on that point. Both internal and external devices require an audio outlet of some sort, and most offer two options in this area. Usually the choice for personal listening is the headphone set. Manufacturers generally supply a mini stereo headphone jack somewhere on the unit for this purpose. If more control of the output is required, a standard RCA phono pair is usually found on the back of the unit, or the rear of the computer when the device is internal.
Another difficulty that had to be overcome before the CD-ROM came into wider usage was the limited software availability. Early disks and applications were targeted almost exclusively at libraries and publishing houses, due to the enormous amount of storage capacity and the longevity of the medium. While of general interest to academics, this material was not particularly useful to music educators. With further development of the storage and encoding techniques, however, it was found that any sort of digital information could be stored, and this included sound, still graphics, animated sequences, and video, in addition to text and binary applications. Indeed, the CD-ROM format was particularly appropriate for this purpose. as the size of these files is often too large to be stored easily on smaller media such as floppy disks.
While perhaps not occurring with the speed some would wish, the pool of available programs has steadily increased, with solid, useful material now available in a number of areas. A recent edition of The Australian Apple Macintosh Product Guide (1992) lists over 400 CD-ROM titles. Topics that may be of interest to teachers of K-12 include musicology, music history, theory, music education and related arts. There is a wide variety particularly in the last category, and this includes art, theatre, ballet, opera, architecture and photography. Obviously, well designed material in these areas can make the teacher's job much simpler, and the learning process much more rewarding for the student, when used in conjunction with a sound curriculum. A large number of reference works is also available in this format, and while not specifically impacting upon the music education area, the growing emphasis on this area indicates that music references must address it or be left behind in the rush toward the twenty-first century.
As mentioned earlier, computers most frequently communicate through a standard called SCSI, pronounced "scuzzy". This is a relatively universal protocol that enables computers to communicate with a large variety of external devices or peripherals, including printers, hard disk drives, optical scanners, monitors, etc. It is a very simple connection to make when using any external CD-ROM unit. Each SCSI device usually includes driver software that lets the computer identify the device, and communicate with it through the SCSI port. Once installed, this software is invisible during normal operation.
Another standard that is gradually disappearing is the DMA or Direct Memory Access protocol. This style of connection was often found in less expensive machines such as the Atari, but is being replaced in favour of the more reliable and standardised SCSI interface. IBM style computers can use this interface protocol, although an optional card must first be installed. One must bear in mind that these connections are only necessary in the case of an external CD-ROM unit. Internal units are, of course, pre-wired.
The next concern is that of the visual aspect of the presentation. For this the usual VDT (video display terminal) may suffice, provided that the participating group is small. Where it is desirable for greater numbers to participate, alternatives must be considered. Occasionally, simply providing a larger monitor will solve the problem, although from a financial viewpoint, it is often more cost effective to purchase a liquid crystal display panel at approximately the same cost.
This unit is placed on a normal or high output overhead projector, and may be used to provide visual information to large numbers of participants. Modern units have overcome many of the early disadvantages of this technology, which included low resolution, inability to 'keep up' with rapidly moving animation, and limited colour output. It must be noted that the effectiveness of such units is directly related to the output of the overhead projector, and that it is worth purchasing the best in order to project a coherent image in less than total darkness.
At the upper end of the projection scale are two entries, the LCD Projector, and the Video Projector. The LCD Projector combines the technology of the LCD panel with a high output light source in one unit, thus making it more convenient and somewhat more reliable than the panel, in the sense that there is no uncertainty regarding the light source. However, it is generally thought that the Video Projector is the best option when presenting to large groups where resolution, accuracy in movement and image size are of the utmost concern. These usually contain three separate lenses and video outputs, one each for the three primary colours, which are then combined to form one image on the screen.
In examining the audio requirements, we must be sure to provide adequate if not exemplary equipment in this regard. The two most common forms of output have been mentioned earlier, those of the stereo RCA phono jack, commonly found in home stereo equipment, and the mini-jack that is the familiar connection for today's smaller headphone/ earpiece units. The logical connections to be made here would be from the stereo RCA phono jack to a stereo amplifier via an appropriate stereo cable for a group, or, in the event of a single listener, from the mini-jack to a headphone/earpiece. This solution will carry sound from an audio track on the CD to the participants, but will not suffice for audio routed to the computers built in speakers.
In the event that audio has been digitised for playback through the internal sound system of the computer and not encoded on the CD itself, one additional step must be taken. Usually an output port, often in the form of a mini-jack, is found on the rear of the computer. This port may be used to connect a headphone/earpiece for a single listener, or routed through an appropriate cable and adaptor to an amplifier for group use. It should be noted here that this signal is usually monaural, rather than stereo.
Regarding the software requirements, of course the decision will be in large part based upon the computer platform in use. Generally, it must be assumed that this will be either one of the numerous pc clones or Apple Macintosh, since these are certainly in the majority in schools. Software may be provided on floppy disk, which is then installed on the local hard disk drive. If this is the case, it is accompanied by an audio CD, as is often the case with the Voyager Companion Series for the Macintosh. The other main package type contains both applications and audio on the same CD-ROM disc. The software still needs to be installed on the hard disk drive for speedy access, but it is a more convenient process for the user than juggling upwards of five or six disks as in the other process.
As this information is digitally encoded, it may be accessed by the computer in a random fashion. To visualise this, imagine an LP record. Information, in this case music or audio, is organised in segments located in bands on the record. If we wanted to listen to band five, we would position the tone arm over that band and drop it, without having to listen to the bands preceding it. This same principle applies to most digital information, including the optical disc. Unlike the LP, however, where the selection of segments smaller than the band is problematic, it is possible to locate information on a compact disc to within 1/75th of a second. The cassette tape, on the other hand, presents its information (sound) in a linear fashion, where one generally must listen to all of the selections in order, or search by trial and error for the desired location.
In 1974 work began on the technology necessary to store and retrieve digitised sound on an optical disc by Philips and Sony (Pohlmann, 1989). While work was carried on at approximately the same time, the two companies approached the problem from different aspects. Philips concentrated on the actual mechanical process of storing and retrieving information from the disc, while Sony was more interested in the algorithms to enable accurate, errorfree storage and reproduction. The melding of these two technologies led to the development of the audio CD. In 1978-9 interested manufacturers established a standard for this process. While this is true for the audio CD, there are over twenty standards or formats in use in CD-ROM discs.
There are a number of advantages to CD-ROM storage. Random access has already been mentioned. Data types can include still graphics, photos, video, sound, animation, simple text and application programs. The medium is particularly valuable for video and other files that are typically beyond the capacity of other portable storage media. The optical disc can hold between 650 MB and 782 MB of data, depending upon format.
Physically, the disc is a thin layer of reflective aluminium substrate sandwiched between two layers of transparent plastic. One side of the substrate is pitted, with each pit being used as a change in the bit stream when being read by the laser. There are over three billion pits per CD (Pohlmann, 1989), arranged in a spiral from outer to inner edge. If this spiral were to be uncoiled, it would stretch over three miles, and if each pit was the size of a grain of rice, the diameter of a CD would be one half mile wide (Pohlmann, 1989).
The storage capacity of the CD is truly astounding. It is capable of storing the following information: 1,500 floppy disks, 275,000 pages of double spaced type, 18,000 pieces of graphics, and over 3,600 still video pictures (Pohlmann, 1989). The US Navy investigated the possibility of using CD-ROM to reduce the amount of paper aboard naval ships. They found that a cruiser carries about 5.32 million pages of documentation, weighing almost 36 tons. The amount of paper stored above the main deck had an adverse impact on the ship's stability. They found that, in theory. that mass of paperwork could be reduced to about twenty CD-ROM discs, weighing a total of 280 grams (Pohlmann, 1989).
Information on the CD-ROM is stored in frames, which consist of a timing header, subcode to identify the type of data, then the actual data. This is followed by error checking information, then a second data packet, and finally a second error checksum (Pohlmann, 1989). This structure allows for the wide variety of information that it is possible to store. It provides for great accuracy, both in the error correction of the data itself, and in the transfer of timing information for the data that is temporally sensitive, such as animations, audio and video data.
There are a number of compact disc formats, but perhaps the most familiar is the audio CD. The format is similar to that mentioned earlier, however, slightly more information can be stored, for a total of approximately 782 MB of information. A playing time of up to 74 minutes and 33 seconds is possible. An apocryphal tale of how this figure was arrived at maintains that Philips asked the famous conductor Herbert von Karajan how long the CD should be, and he replied that it should be long enough to hold his recording of the Beethoven Ninth Symphony (Pohlmann, 1989). Typical audio specifications are as follows: dynamic range > 100 dB, signal to noise ratio 2100 dB and channel separation 2100 dB (Pohlmann, 1989).
The CD-ROM format typically holds 660 MB of information, the trade off being indexing and search structures necessary for accessing that information. The vast amount of storage has made this medium the preferred choice for electronic publishing of massive projects, such as encyclopedias and other reference works. The CD-ROM disc identifies itself through a special bit of data in the Q subcode of the frame.
Virtually any large project that does not require frequent updating is a candidate tor this type of distribution. Some typical projects would include software bundles, such as Microsoft Office; large operating systems; online databases, such as ERIC or PsychLit or Dissertation Abstracts Online. Reference materials have been mentioned, but encyclopedias, dictionaries, and others such as the Oxford Writer's Bookshelf are good examples of this category. Directories and back issues of journals are increasingly available in this cost effective medium as well. Finally, graphics and font libraries and parts catalogues are logical inclusions in this format.
Other popular CD formats include CD-I (Compact Disc Interactive), DV-I (Digital Video Interactive), CD+MIDI and the new Kodak Photo CD. CD-I format is usually product specific - that is, it can only be read by a specific machine, one that is often not a fully functional computer. This format can store digital video in either PAL or NTSC formats and audio. Different compression rates can be used for optimum content. While popular for a while, this format seems to be losing ground to other formats at the present time. DV-I is a popular choice among training in interactive applications, including medicine, aviation and maintenance. Again, depending on the compression rate used, variable amounts of data can be stored.
Of particular interest to music educators is the CD+MIDI format. MIDI data can be stored in unused subcode bits, which amount to 25 MB on an entire disc. This means that data utilising all 16 MIDI channels can be sent to MIDI devices while either text or graphics or both are being displayed on the terminal. One possibility for instruction is a score display on the terminal, with MIDI information providing an accompaniment for the user.
A recent development in the CD-ROM area is the photo CD. Kodak has developed a method of storing photographs in CD format. These discs are known as multi-session discs, as they can be written to more than once, enabling more than one set of photos to be stored. Each photo is stored in four different resolutions, one of which is suitable for the consumer's home use. Players are available from Kodak as well as from third party manufacturers that can project the images on a television set. This is the lowest resolution. Multi-session CD-ROM units can show the second and third resolutions, with the top resolution being reserved for specialist players. The discs have a projected price of $15-20 per disc, with each image being about one dollar to store. This storage technique offers great possibilities for the inclusion of high definition photos in educational software programs.
The user should create a folder for the software and install it in the new folder. Occasionally there are files that need to be copied to the system folder as well. These might be font or preference files that are needed by the program. Some programs have an unusually complex procedure for installation, and will need to be installed each time they are run. These programs are often based on the popular HyperCard authoring structure.
The two most popular delivery systems for music programs seem to be HyperCard and MacroMind Director, or a combination of both. Each has advantages and disadvantages from a programming aspect, but these really don't make much difference to the end user. HyperCard is used extensively by the Voyager companion series, which has an extensive catalogue of music CD-ROM offerings. One advantage of using HyperCard is the broad based use in the computing community means that it is a familiar interface to many users. Some disadvantages are that it is rather slow by modern standards and has limited graphic and animation possibilities. For instance, while it is possible to display colour in HyperCard. it is a laborious task and much easier in other computing engines.
MacroMind Director, on the other hand, manages colour and animation very well. The problems arise when complex branching and navigational tasks are attempted. It is for this reason that many software publishers, such as Warner, use a combination of both programs - HyperCard for navigation and overall structure, and MacroMind for colour graphics and ant/nation duties.
While there are some differences in the design and presentation of the programs surveyed, there are a number of factors that remain constant across the range. All programs may be presented in different streams or levels. These may be differentiated by obvious factors. such as the amount of detail offered, or by something as simple as the language of the libretto provided tor the user. All offer some means of allowing the user to personalise the presentation, or to record personal observations during use. All provide some form of interactive glossary, where selecting a word or phrase furnishes a definition or explanation. Finally, all make use of the research that indicates a game format can inspire greater learning of material.
Brewer, Bryan (1986). Compact disc interactive audio. In S. Lambert & S. Ropiequet (Eds.), CD-ROM: The new papyrus. (pp.273-290). Redmond. WA: Microsoft Press.
Einberger, John ( 1987). CD-ROM characteristics. In S. Ropiequet (Ed.), CD-ROM. Redmond, WA: Microsoft Press.
Pohlmann, Ken C. (1989). Principles of Digital Audio. Indianapolis: Howard W. Sams & Company.
Pohlmann, Ken C. ( 1989). The compact disc: A handbook of theory and use. Oxford: Oxford University Press.
Pohlmann, Ken C. ( 1991). Compact discs. In Glen M. Ballou (Ed.), Handbook for sound engineers: The new audio cyclopedia. Indianapolis: Howard W. Sams & Company.
| Author: Dr Thomas Hughes, Coordinator Software Development Centre, Sydney Conservatorium of Music, Sydney University, Macquarie Street, Sydney, NSW 2000. Email: thughes@extro.ucc.su.oz.au
Please cite as: Hughes, T. (1994). CD-ROM in the music classroom. In J. Steele and J. G. Hedberg (eds), Learning Environment Technology: Selected papers from LETA 94, 112-116. Canberra: AJET Publications. http://www.aset.org.au/confs/edtech94/ak/hughes.html |