Digitization Of The Book: A Report On Present Trends

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• A New Generation of Audio Books
  • 6.3.1 Compact Disc-Digital Audio
  • 6.3.2 High Density Disc (DVD)
  • 6.3.3 Transmission VS Distribution Medium
  • 6.4 Compression

A New Generation of Audio Books

6.3 Phase II : Future Potential Digital Distribution Media

6.3.1 Compact Disc-Digital Audio

Although a standard CD will accommodate large electronic text files and a limited number of visual and/or audio clips, it will hold only a maximum of 80 minutes of recorded stereo audio (the typical amount of recorded audio on a music CD is 65 minutes, whereas an entire electronic encyclopedia can be contained on one CD). CD storage capacity, is typically 650 megabytes.

CD's are used as an interim medium, between a digital or analog master, or as the distribution medium itself. An 'interim' recordable CD is used to transfer the digital audio to a glass disc, and from this glass disc, one 'father' is produced. This process is used by some Canadian companies for high volume duplication.

6.3.2 High Density Disc (DVD)

DVD is being introduced as a replacement for the VHS format. This disc format, which has recently emerged on the commercial market, has great potential for distribution of human voice talking books, as its storage capacity per disc is much greater than other formats. It can accommodate a range of approximately 4.7 gigabytes to 17 gigabytes per disc. Each disc has a 5.1 channel capacity with data capability. Most unabridged talking books would therefore fit, uncompressed, onto 1 high density disc. Needs for both large storage capacity and high quality audio would be met. DVD players will play both DVD's and conventional CD's. It is predicted that DVD will eventually replace data discs like CDROM's and once established in the market place, may prove to be very effective as an archiving medium for digital audio and/or as a future distribution medium for talking books.

The North American format for DVD differs from the European. The American standard will be Dolby Digital AC-3 audio; the European version will use MPEG-1 audio coding. The commercial world will undoubtedly develop a system to decode/transfer information from one format to the other, but this additional process will frustrate and deter international resource sharing of digital talking books.

6.3.3 Transmission VS Distribution Medium

Digital audio can be distributed over a network but talking books with larger audio files require large storage capacity for sending and receiving. Digitized audio files are vast in relation to most of the existing network capabilities and at present take a great deal of time to transmit. The transmission of an uncompressed digital audio file, such as a 6 hour talking book would take approximately 1/2 hour to retrieve/download. (See "The Internet".)

6.4 Compression

Digital audio files can be compressed to reduce storage requirements. Recorded speech can be compressed to a greater degree than music before audibledegradation of the sound quality occurs. Different modes and levels of compression are available. MPEG 2 use is at present very common, but MPEG 3 is now available. Compressed audio files cannot be played on commercial audio CD players, as they must be decoded for use. The use of compression (coding) and decompression (decoding) slows the restitution of the files.