Before DVD

The origin of DVD lies in the first broadly successful optical format – the Compact Disc. Since the introduction of the audio Compact Disc in 1982 and the CD-ROM in 1985, the CD has become a universally accepted carrier for music, data, and multimedia entertainment. CD-Audio was by many measures the most successful new consumer entertainment format of its time. CD-ROM has enhanced and enabled many aspects of the desktop computer revolution, and is now included as a standard item on most desktop and laptop PCs (although they are quickly being replaced with CD-compatible DVD-ROM drives).

Since the CD first appeared, consumer electronics and CD manufacturing companies have been working on new techniques to boost both the storage capacity (74 minutes or 650 Megabytes (Mbytes)) and the data transfer rate (1.4 Megabits per second (Mbps)) of the format. In 1993, Nimbus Technology and Engineering announced the first double-density CD format, which supported two hours of MPEG-1 video playback. This was the first demonstration that CD technology could carry high-quality video as well as audio, and suggested that a new format might be on the horizon.

By 1994, cable, satellite, and video-on-demand services were making strong inroads into the home video entertainment market, competing for the consumer’s time and money. Responding to the potential erosion of revenues from VHS sales and rentals, the home video industry recognized the need for a new consumer video format that would deliver superior picture and sound quality. Encouraged by the CD’s role in revitalizing the record industry, major Hollywood film studios formed an advisory committee to define a set of requirements for a similar optical video format.

Table 1.1 Initial studio requirements for an optical video format.

The committee’s recommendations are listed in Table 1.1.

By January of 1995, two prototype formats emerged: the Super Density (SD) format proposed by Toshiba and a consortium of partners, and the Multimedia Compact Disc (MMCD) proposed by Philips and Sony.

With the prospect of a ‘Beta versus VHS’ format war looming on the horizon, and under pressure from the studios and computer companies, the consumer electronics manufacturers reached a general agreement in December 1995. They formed the DVD Consortium to agree upon a single, unified specification for their next-generation video format. (The original members of the DVD Consortium were Hitachi, JVC, Matsushita, Mitsubishi, Philips, Sony, Thomson Multimedia, Time Warner, and Toshiba.) The Consortium then created a number of committees or ‘working groups’, each responsible for one aspect of the new format (physical construction, data organization, etc.).

The formats emerge

While video playback was the original inspiration for the new optical format, DVD Consortium members knew that the expanded capacity and higher data rates of DVD made the new format well suited for many other applications. In addition to working on the underlying DVD-ROM format, on which the DVD-Video would be built, the Consortium envisioned a third read-only variant which could serve as an eventual replacement for the venerable Audio CD. It also defined physical variations, DVD-Recordable and DVD-Rewritable, to allow for different types of recording.

In light of all the possible uses for optical media storage systems, the specifications for DVD were divided into several ‘books’, designated A to E. The DVD Forum later added a Book F. The DVD books are listed in Table 1.2.

Table 1.2 DVD books A to E.

Recalling how the acceptance of the CD-ROM format had been slowed by compatibility problems between its various flavours (CD-I, Video CD, Macintosh CD-ROM, ISO-9660 CD-ROM, Photo CD, Hidden data track CD-Audio), the DVD Consortium decided to unify the entire family of DVD formats with a common file system. This new UDF (Universal Disc Format) file system was designed to play back in any computer system and to accommodate writeable and re-writeable variations. With UDF support included on virtually all computer operating systems, any computer with a DVD-ROM reader would be able to access data on a DVD disc, be it DVD-Video, DVD-Audio or the DVD-ROM format.

A dramatic launch

The Version 1.0 specifications for the physical, logical and video parts of the read-only disc (DVD-ROM) were published in September 1996. After finalization of copy protection methods, DVD-Video was introduced into the Japanese market in late 1996, into the North American market in 1997, and into European market in early 1998.

DVD-Video’s growth since its introduction has been dramatic. The following chart compares player shipments for new consumer electronics formats in the years following each format’s introduction.

With year-to-year percentage increases in the number of DVD-Video players sold running in the hundreds, the format enters the new century with an installed base of some eight million worldwide. However, DVD player sales only tell part of the story, because DVD-Video titles will also play back on computer-hosted DVD-ROM drives. Roughly 50 million DVD-ROM drives had been shipped by the end of 1999, and it is estimated that by 2002 more than 90 million will be shipped annually.

Figure 1.1 Cumulative shipments of consumer video and audio formats in the first five years after introduction.

DVD-Audio

In January 1996, the first meeting was convened of the DVD Consortium’s Working Group-4, which is responsible for the DVD-Audio standard. Working Group-4 solicited input from the music recording industry via the trade associations that represent the world’s major recording companies: the Recording Industry Association of America (RIAA), the International Federation of the Phonographic Industry (IFPI), and the Recording Industry Association of Japan (RIAJ). In response to the Working Group-4 request, these groups formed the International Steering Committee (ISC) to coordinate their input into the DVD standards-setting process.

The ISC met with Working Group-4 in May of 1996, commencing a series of meetings and evaluations that would take more than 18 months. During this time the DVD Consortium was enlarged to become the DVD Forum, now made up of more than 100 member companies. (Sonic Solutions is a voting member of the DVD Forum, as well as a member of several working groups, including Working Group-4.)

At the first meeting, the ISC delivered to Working Group-4, a set of technical requirements. Chief amongst these were that the new format support uncompressed high-resolution digital audio; that it allow both stereo and surround sound channel configurations; that it incorporate not only audio but also video and data elements; and that it offer copyright and anti-piracy protections.

Working Group-4 published a draft specification of the new audio format for its members at the end of November 1997. The official Version 0.9 specification was subsequently published in May 1998. To maintain continuity with the CD-Audio format, these specifications required that DVD-Audio players also play Audio CDs.

At the same time, because of certain requests made by the ISC to Working Group-4 in the spring of 1998, a number of changes were made to the DVD-Audio specification. Most notably, to make sufficient room on the disc for longer programs of high-resolution, multichannel sound, the ISC requested that player support be mandated for a ‘lossless’ (output identical to input) compression scheme. Various systems were evaluated, and Meridian Lossless Packing (MLP) was chosen for inclusion in the specification.

The Version 1.0 DVD-Audio specification has now been published, and the process of launching the format worldwide is taking place throughout 2000 and 2001.

Super Audio CD

Super Audio CD (SACD) is built on the physical and logical foundation as the DVD specification (same disc size and file system). Like DVD-Audio, it is intended to support high-fidelity delivery of both stereo and multichannel sound. Super Audio CD, however, is based on the Direct Stream Digital (DSD) audio coding technique.

Unlike PCM encoding (the encoding technique used for the CD and in the DVD-Audio specification), DSD does not attempt to measure the amplitude of an analog wave at discrete points in time (44 100 times per second for a CD, for instance). Rather, it measures whether a wave is rising or falling, and it does so at a sampling rate (2.8 million times per second, or 2.8 MHz) that is many times higher than the rates used for PCM. This technique based on over-sampled changes in the amplitude of an audio signal (‘delta-sigma’ encoding) has some very attractive properties. For instance, quantization noise is confined for the most part to areas of the audio spectrum where it is imperceptible to the human ear.

Sony and Philips originally proposed DSD for inclusion in a future consumer audio recording format. The companies subsequently developed and proposed a new read-only disc format –Super Audio CD – to the content holders, publishers, and replicators who make up the community of Compact Disc licensees.

Version 1.0 of the Super Audio CD specification has now been published as the ‘Scarlet Book’ (a reference to CD-Audio’s ‘Red Book’), and a two-channel version of the players was released in Japan in the late spring of 1999. In the US, a combination DVD-Video/SACD (two-channel) player has been announced by Sony and a multichannel SACD player announced by Philips, both scheduled for shipment late in 2000.

At the time of this writing, the precise relationship between Super Audio CD and DVD-Audio is still somewhat unclear. There have been some suggestions that DSD be included in DVD-Audio, but to date DSD playback support has not been mandated by the DVD Forum. There is, however, a ‘data definition area’ designated in the DVD-Audio specification as ‘reserved for future use’, leaving the door open to future inclusion of DSD as an optional coding technique for DVD-Audio. Additionally, there have been some very specific statements by members of the Super Audio CD group that DVD-Audio player manufacturers are completely free to incorporate Super Audio CD support into their players. Thus it is entirely possible that next-generation players will be built to accommodate playback of DVD-Audio and Super Audio CD, in addition to CD (required of every DVD player) and, probably, DVD-Video (see the discussion of Universal players in Chapter 5).

Further discussion of Super Audio CD is beyond the scope of this book.