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Will DVD-Audio Ever Be Sound?
By David J. Weinberg
There have been a lot of different formats (for manyxtoo many formats) dominating consumer audio with increasingly shorter life cycles.
The phonograph record ruled for around a century. The audio cassette (a Philips development) reigned for about a quarter century. The Compact Disc (Sony-Philips) has been king of the market for the last decade, and isn't quite ready to abdicate, or be dethroned.
The public remembers, some with resentment, the 1970's quadraphonic debacle and the 8-track tape.
The industry tried to get us to accept DAT and DCC (neither of which made it), and is still working on us to endorse the MiniDisc (Sony).
With each of these new formats, we were told we had to buy new equipment and new software, often to replace software we already had.
Meanwhile, the computer industry changes hardware and "upgrades" its software (often, seemingly, without debugging it) so fast that everything is obsolete before it's released.
Future shockxresistance to changexis truly a part of man's psyche, and the increasing rate of change exacerbates that reaction.
The most recent contrivance is the DVD (partially a Sony-Philips development, with compromises made to unify the standard), which seems to be on the threshold of replacing the LaserDisc as the high-quality consumer video medium. It is being touted by the computer industry as the next "greatest" removable, reasonably-priced multi-media software distribution mechanism, trying to replace the CD-ROM. Development of reasonably-priced WORM and rewriteable DVD technology, which is well under way, will truly sign the death knell for computer use of the CD-format disc.
There is a possibility that the DVD will replace the CD as the consumer digital audio medium of choice, but audiophiles and the professional audio community will not accept perceived sonic quality compromises imposed by psychoacoustically-based data reduction schemes (like Dolby® Digital, MPEG and DTS® Digital Surround). The industry has been on a quest for the digital audio system parameters necessary to provide a format that will be affordable and buildable without becoming prematurely obsolete and inadequate. A lot of money and many careers are at stake.
This has driven the audio industry into what seems to be a reasonably civil cold war (cool civil war?) to control creation of a DVD-Audio specification for creation of DVD-Audio discs and as a basis for the design of DVD-Audio recording and playback equipment for the next 15-20 years. This would be nice, but it seems unrealistic in today's dynamic technological world and intricate business environment.
As an inhibiting factor, the record industry feels no need for a new, higher quality medium. The public is quite happy with the CD. Audiophiles, who have an insignificant financial impact on the record industry, always push for higher quality (as they should), but are generally not interested in, or have systems capable of, surround sound; thus the multichannel aspects of DVD-Audio are mostly wasted in the audiophile market. In contrast, the record industry also sees multichannel systems as the most rapidly growing portion of the audio marketplace, and wants their share.
It is in this cloud of complexity and competition that various groups chose to pursue a high quality audio standard to take advantage of the large storage capacity and high bit rate of the DVD format.
The Players
There are several organizations addressing DVD-Audio standard development, including:
A. The Audio Engineering Society's Subcommittee Task Force SC-02-M on High-Capacity Digital Audio;
B. Working Group 4 (WG4) of the DVD Forum;
C. The International Steering Committee of the recording industry;
D. The Academy for the Advancement of High End Audio;
E. The Acoustic Renaissance for Audio;
F. The Moving Picture Experts Group MPEG-2 audio standardization committee; and
G. Sony-Philips.
The Questions
These organizations are addressing as many facets of DVD-Audio as possible, including:
1. Sampling rate (48kHz, 88.2kHz, 96kHz, 192kHz; 2.8224MHz, etc.);
2. Word length (16, 20, 24 bits per sample, or an allowable range; 1-bit);
3. Type of recording (PCMxlike a CD; 1-bit delta-sigma modulation);
4. Number of channels (2, 4, 5.1 or 6; down-mix in the player or separate mixes on the DVD);
5. Compression (lossless or none);
6. Backward compatibility (Include a Red Book-compliant CD-encoded layer? Should that layer support Dolby Digital and/or DTS Digital Surround encoding?);
7. Sideways compatibility (How much should the standardized DVD specification be changed to accommodate DVD-Audio? How much does it need to be changed?);
8. Copyright protection (How much will the protection scheme affect the audio quality? How much will it inhibit home copying, or even playback, while having no deleterious effect on the professional counterfeiter [an argument I, and a few in the industry, have had against Macrovision on video for years]?);
9. How to avoid immediate obsolescence, keep costs down, and accommodate the next 15-20 years of technological development without requiring a 'standard' rewrite;
10. Each company involved wants to determine how to get its competitive edge (maximize its profits); and
11. Can musicians, audiophiles (Gosh, could the consumer actually be involved?), and record industry and recording experts afford to take the time necessary to explore the possibilities, potentials and implications of various approaches to ensure that as many needs as possible are met, and as many problems as possible are averted; or, what forces are driving a 'rush to verdict'?
The Games
A. The Audio Engineering Society's Subcommittee (AESSC) Task Force SC-02-M on High-Capacity Digital Audio, chaired by John Eargle and Tomlinson Holman, was formed in 1995 and assigned task AES-X38. Its goals were to:
A) Describe options for advanced audio systems, including utilization of high-capacity media and corresponding interconnection systems;
B) Get everyone involved in the standardization process, including artists, recording engineers, producers, manufacturers, etc.; and
C) Move things along as quickly as reasonably possible.
Their report (#AES-X38-D26; dated November 4, 1997) is available at "http://www.aes.org/standards/reports/SC-02-M-REPORT.html" or "ftp://REPORTS.STANDARDS@aessc.aes.org/SC-02-M-REPORT.PDF",
and in the December 1997 Journal of the AES.
This task force has received appreciation from other groups for its efforts to define the issues that must be addressed to ensure an effective standard.
The AESSC SC-02-M task force report recognizes that professional systems need higher sonic quality and more capabilities and functions than consumer playback units, to prevent creating a final mix that compromises the capabilities of the DVD-Audio disc. It proposes that the professional systems operate in a non-compressed linear PCM format (or one based on linear PCM), due to the editing complexities of compressed bit streams. It also recommends that DVD-Audio discs carry useful header information in addition to fixed-bit-rate data streams for multichannel and 2-channel audio (since the recording and mix engineers would rather create their own 2-channel mixdown than trust a computer algorithm). One key point is that separate standards may be needed for various points in the recording chain. As the primary subjects to be considered, the report delineates:
1. Audio coding (include lossless compression),
2. Sample rate (it recognizes that 60kHz might be high enough, 96kHz is strongly desired, yet notes that 88.2kHz is twice the CD sample rate),
3. Word length (based on real-world dynamic range requirements, 20 bits is adequate for consumer media, while up to 24 bits is useful for professional systems), and
4. Number of channels (carry both 2-channel and 5.1-channel bit streams).
The report's sections on psychoacoustics and concert hall versus listening room acoustics exhibit the influence these subjects have on the proper definition of an effective DVD-Audio standard. The report strongly recommends scientific listening tests. It also suggests the possibility of a 2-layer DVD, with one layer compliant with the CD Red Book standard, enabling a single disc to be playable on the millions of existent CD players, including portable and auto units, and on DVD players; this allows the consumer to purchase a single disc for simple 2-channel CD or DVD playback, which also carries the data needed for sophisticated multichannel DVD-based playback systems.
B. Working Group 4 (WG4) on DVD Audio is part of the DVD Forum.
The DVD Forum used to be the DVD Consortium of ten companies: Hitachi Ltd., Matsushita Electric Industrial Co. Ltd., Mitsubishi Electric Corporation, Philips Electronics N.V., Pioneer Electronic Corporation, Sony Corporation, Thompson Multimedia, Time Warner Inc., Toshiba Corporation, and Victor Company of Japan. These ten companies are now the foundation of the DVD Forum's steering committee, which can be no more than 20 companies. The DVD Forum boasts more than 120 member organizations, and is growing. Note that a major portion of the DVD software producers and DVD player manufacturers are represented, and that some of the companies do both.
Since the DVD Forum publishes and holds the copyright on the DVD standard, no changes occur without its blessing.
WG4, one of 11 working groups created by the Forum, specifically addresses DVD-Audio standardization. Representatives of Sony, Philips, Matsushita and Toshiba head up this group. All DVD-Audio proposals and concerns ultimately come through WG4 for approval before being submitted to the DVD Forum for confirmation.
WG4 initially concluded that the DVD-Audio disc should (from "DVD-Audio Format" by E. Funasaka and H. Suzuki, both of JVC; presented at the September 1997 AES convention):
1. Support pure audio with value added content (like video, text, graphics, etc.);
2. Be compatible with the DVD Read-Only Disc family;
3. Provide high quality and multichannel sound;
4. Provide advanced, easy-to-use disc navigation features;
5. Support copyright management, copy protection, and anti-piracy features; and
6. Allow for future extensibility to accommodate even higher audio quality, such as 192kHz and 1-bit coding.
WG4 has not made any final declarations, yet. For example, while WG4 has been considering proposals that include video data, there is at least one design that is audio-only, and there has been no final decision on including even lossless compression of the digital audio bitstream. However, none of the lossy compression schemes like MPEG-2 AAC, Dolby Digital, DTS Digital Surround, and SDDS, are being considered as part of the primary high quality audio encoding scheme.
C. The International Steering Committee (ISC) of the recording industry is made up of the International Federation of Phonographic Industry (IFPI); the European Recording Industry Association (ERIA), the Recording Industry Association of America (RIAA) and the Recording Industry Association of Japan (RIAJ).
They saw others, particularly WG4, controlling actions that affect them (and possibly their profits) without their involvement, so they formed the ISC to ensure that the recording industry has its say in the process and its effect on the result.
In May 1996 the ISC adopted 13 requirements for the DVD-Audio disc:
1. Active Copy Management System (ACMS)xThe DVD-Audio standard must be backward compatible with existing copyright management techniques;
2. Copyright IdentificationxThe ACMS must be part of the audio bitstream;
3. Anti-Piracy MeasuresxDVD-Audio must include source identification codes, recorder identification codes (including brand, model, and serial number) and other data in the audio bitstream;
4. CompatibilityxDVD-Audio discs must be playable on all DVD players, and have a CD layer;
5. FormatxThe DVD-Audio standard must allow for additional audio, video and data on the disc;
6. Conditional AccessxThe DVD-Audio standard must provide for free-access to material on the disc, as well as controlled-access to select material on the disc;
7. Sound Quality SpecificationsxThe DVD-Audio disc must provide two "high quality" stereo channels and an additional six "high quality" channels, scalable and using an agreed-upon lossless compression scheme;
8. Archive, Master, TransferxTransfer of existent material to the DVD-Audio format must not compromise its quality.
9. Accessibility And Disc FunctionsxSeveral mandatory and optional items of information must be provided for (but not necessarily provided);
10. Packaging;
11. Disc DurabilityxThe DVD-Audio disc must survive better than the CD;
12. Number Of Sidesx"The recording industry favors a one-sided disc format;"
13. Disc Sizex"The recording industry favors a 12-cm disc."
The ISC was planning to conduct listening tests of various word lengths and data rates, but proposals have been received that would offer a number of choices, letting the individual artist and engineer exercise their preference. This obviates one of the primary motives for centralized listening tests.
In November 1997, the ISC announced it will not attempt to select and recommend a single format, but will allow the industry and marketplace to make that choice. It does hope that the industry will come together on a single format that remains compatible with the large CD collections of many consumers.
The ISC appears to be concentrating on copyright and anti-piracy concerns, which have always seemed to be the central concerns of the recording industry.
D. The Academy for the Advancement of High End Audio (AAHEA). President Joseph Piccirilli leads the AAHEA in efforts to improve the market share and profitability of home theatre and high-end audio. He continues active lobbying, and consulting for, the other Players to encourage as high a sonic quality DVD-Audio standard as feasible.
Piccirilli believes the consumer is confused about the many audio formats in recent years and the lack of a single DVD-Audio standard. He sees the CD as an excellent technology satisfying most of the public needs and a great marketing success. He believes we should continue to advance the state of technology and simultaneously pursue a new higher quality standard. Piccirilli views DVD-Audio as a niche market, and expects it will take 10 years for DVD-Audio to become widely accepted and a reasonable economic success.
E. The Acoustic Renaissance for Audio (ARA). ARA's founder is Hirokazu Negishi of Canon Inc.'s R&D Headquarters. J.R. (Bob) Stuart is Chairman of ARA (also Chairman of the Meridian Audio Groupxa high-end audio equipment manufacturer; and on the board of the AAHEA).
The ARA has been quite active. From 1995 through 1997, and after thorough study, Bob Stuart, as ARA Chairman, has issued several pertinent documents for deliberation among parties involved in the DVD-Audio standard definition. The ARA doesn't presume to have all the answers, but it has addressed many appropriate questions, and presented logic and sound reasoning for consideration.
The ARA believes that the DVD standard, as published by the DVD Forum, needs very little adjustment to also provide proper standardization for a high quality DVD-Audio disc. The primary modifications required, which the ARA feels will not add cost to currently-proposed video DVD players, are:
1. Include an option to use a constant-bit-rate losslessly-compressed linear PCM-encoded audio bitstream, and a delta-coded bitstream (like Sony's DSD), in addition to the current mandatory PCM or AC-3 encoded audio track;
2. Include the ability to properly handle a variety of channels (3, 4, 5 or 6) and Ambisonic B-formatted multichannel audio by expanding and more thoroughly specifying the header information;
3. Incorporate pre-emphasis with the 88.2kHz or 96kHz sampling rate (ARA claims that pre-emphasis optimized for this application can give 21-bit performance from as few as 14 bits); and
4. Include a second, CD-Red Book-compliant layer with the 2-channel mix on audio-only DVDs.
The ARA's position is that these modifications will obviate the need for a separate DVD-Audio specification, that the modified specification will also support high quality audio with video (like a music video), and that only audio DVD players specifically designed to take advantage of the added functions and capabilities will require added hardware, such as a digital audio output to feed external DSPs (particularly for the 20-bit/96kHz bitstream or Ambisonically-encoded audio).
The ARA recommends more stringent performance for the professional recording and preparation of the DVD than for the released disc, to ensure the consumer gets the maximum quality available, and to allow the flexibility needed to optimize the resultant product under a variety of source and production conditions.
Bob Stuart (in his position at Meridian Audio) has been instrumental in developing a very highly-regarded lossless compression system. One of its most important features is the benign effect of the system's failure. Any real world lossless compression system will some times encounter a signal it is not able to handle, either due to inadequate buffer storage, inadequate bit rate, or some other factor. What the system does in this situation is most critical. A corollary most of us have encountered is amplifier clipping: As Tomlinson Holman pointed out so clearly more than 15 years ago, all amplifiers will clip sometimes, and how different amplifiers react goes a long way to determine how they sound at loud levels, and how safe it is to connect your speakers to them. An amplifier that handles clipping nicely will not have nearly as edgy (or as dangerous) a sound during clipping as one that reacts badly. The same type of effect occurs in lossless compression systems.
F. The MPEG-2 audio standardization committee of the ISO/IEC JTC1/SC29/WG11 (also known as MPEG) has developed MPEG-2 Advanced Audio Coding (MPEG-2 AAC) to provide, as was its mandate, sonic quality audibly indistinguishable from the source (as specified by the International Telecommunications Union, Radio Communication Bureau) at data rates no higher than 384 kilobits per second for 5 full-bandwidth channels. Tests performed at the BBC and at NHK show that the ITU-R criteria were met, even though lossy compression was used. Regardless, this is not of value for DVD-Audio because lossy compression is unacceptable. Plus, the ITU-R criteria might not be stringent enough to satisfy recording engineers (for mastering and archiving their creations) or audiophiles.
G. Independently and within the above-named groups, the Sony-Philips coalition is promoting their Direct Stream Digital (DSD) 1-bit delta-sigma modulation technology to be the DVD-Audio standard technology. These two companies have demonstrated their ability to foster a world-wide standard (the audio cassette and the CD, for examples), and their efforts have complicated the DVD-Audio standardization effort from several perspectives:
1. Their money and large market presence make them difficult to ignore:
2. Their vigorous support of the single-bit scheme prevents any new standard from locking in PCM-type encoding (although, forcing a more open standard is not in itself a bad idea);
3. The other groups will have to expend extra effort, money and time researching the performance and implications of the delta-sigma modulation scheme to determine its relative value; and
4. The other groups will have to expend a lot of extra energy, resources and funding to prevent Sony-Philips establishing the standard by themselves.
More Parties Heard From
Many parts of the music and audio industries are taking DVD-Audio standard development seriously enough that they are actively communicating across professional boundaries. Examples include multichannel demonstrations arranged by the AES Subcommittee Task Force and presented to the National Academy of Recording Arts and Sciences (to help their members understand potential uses and benefits of multichannel recording), and similar demonstrations at the University of Southern California during the International Alliance for MultiChannel Music conference. Some industry gurus intimately involved in the process are pursuing and encouraging involvement on an even broader scalexsuggesting that consumers be represented and involved, to ensure their perspective on needs and desires are addressed. After all, if we don't want them, we won't buy them, and the whole effort will be for naught.
Two three-hour sessions related to DVD-Audio were held at the September 1997 Audio Engineering Society convention:
A. W-3x"The Audio Implications Of DVD"; and
B. W-12x"24-Bit/96kHz Mastering: Where Do We Go From Here?"
A. W-3 x "The Audio Implications Of DVD." This session was chaired by David Kawakami (director of New Business Development for Sony Electronics in the U.S.), with panelists Bob Harley (Fi Magazine), Bob Ludwig (Gateway Mastering Studios), George Massenburg (George Massenburg Labs), Jordan Rost (Warner Music Group), and the ubiquitous Bob Stuart.
Part of keeping this session in perspective requires recognizing that David Kawakami represents Sony, which wants DSD to be at least part of the DVD-Audio standard, instead of simply accepting the growing momentum for 24-bit/96kHz lossless PCM encoding. He did try to keep DSD from being specifically addressed, and was quite successful.
This session focused on what George Massenburg called a "flexible open-ended" standard. Some of the thoughts and ideas presented reveal the panelists' depth of thought and concern for the consumer and for the business of music audio:
• Competing technologiesxPCM versus DSDxbolster the push for an open standard, and allow the time to ensure the final product is a good, long-lasting standard, with DSP that can be changed later as technology advances. At the same time, there is a clear need to avoid a format war. Should the decoder engine be defined now, or should it include the decoder algorithm and code in the data bitstream, with a general purpose DSP in the playback machine (which some feel is impractical)?
• No one yet knows what the consumer wants (and will spend money for), including the number of channels. Groups such as ARA strongly support multichannel sound as presenting a more accurate representation of the musical experience, as part of their active pursuit of a high quality audio disc and their concern that the severely-limiting lossy-compression audio could become the only DVD audio carrier.
• The consumer is certainly aware of, and interested in, this new DVD format. To prevent consumer rejection, the standard needs to be a good one, and fixedxnot a "Moving target." The standard must be multichannel, since among other factors, multichannel sound gives the musical artist the largest possible canvas. Many artists and engineers, particularly in popular music, aren't sure what to do with the additional channels yet. The late Michael Gerzon was a strong proponent of including sonic height information in recordings (as in the Ambisonic recording system). Bob Stuart continues to recommend that this not be dismissed, and that the standard include the potential for this.
• The DVD is optimized as a video medium. For DVD-Audio, it is being perceived as a 4.7GByte bit bucket in which formatting, sampling rate, and other parameters can be optimized for high quality audio.
• Some feel that 20 bits is adequate for a released medium, with up to 24 bits for professional equipment being sufficient to allow the complex processing used in program creation without compromising the 20-bit release quality. The group was reminded that the early CD didn't live up to the promise of the standard until effective implementation occurred, and how to use the technology was learned.
• Feeling that the CD will be a viable medium for many more years, the simple relationship between the CD's 44.1kHz sampling rate and 88.2kHz might make it preferable to any other; yet, 48kHz is already the professional standard, and 96kHz is its double. Everyone seems to agree that at least 60kHz is necessary. Most also agree that the benefit of a higher sampling rate is mostly due to simplifying anti-aliasing filter design and reducing the sonic anomalies they inflict.
• Bob Ludwig believes that 96kHz sounds different, and better, than 48kHz; he admits he isn't sure why. Even though he has tried many different tests, he's having trouble defining valid tests and understanding the cause of the sonic difference. Ludwig noted that a complete 96kHz systemxmicrophone through playbackxdoesn't exist yet, and determination of the need or benefit from such a system can't be tested until it is available.
• There is a faction that raised the idea of using fewer bits and/or a lower sampling rate for the surround channels, to lower the overall data rate and storage requirements.
• Some of the professional equipment needed for DSD or 24/96 PCM systems hasn't been built yet, and realizing a true 24-bit D/A was claimed to be impossible for quite some time.
• No one has performed scientifically-designed double-blind listening tests of the different systems under discussion. Should such tests be performed? Or should the standard push the technology as far as it can to preclude limiting the capability of the medium? The standard must be expandable to include capabilities and functions not yet considered, or it will become an albatross.
• The current DVD standard supports up to 8 separate audio tracks. Musicians and engineers prefer to create their own 2-channel mix, rather than permit a computer algorithm to do it for them. Having a 2-channel mix plus a separate multichannel mix on the same DVD is already acceptable. Only the bit stream format and encoding needs to be chosen.
• In addition, many want a second layer to be compatible with the CD Red Book, so the disc could be played on both DVD players and all existing CD players, even though the CD layer would not offer the same high quality or multichannel sound. Having the same program on two separate layers of a single disc has already raised several issues, including whether the fact that dual layer discs have less data capacity per layer will compromise potential sound quality or the programming capacity. Most agree that lossless compression is quite acceptable and would easily overcome any perceived storage space limitations. Everyone agrees that there is no lossy compression scheme to which music should be entrusted.
• There is recognition of the artists' and record companies' concern for effective copy protection.
• On the consumer side, there is a need for inexpensive portable DVD-Audio players.
• R&D is needed in recording and post production tools and techniques, psychoacoustics, playback hardware, etc.
B. W-12 x "24-Bit/96kHz Mastering: Where Do We Go From Here?" This session was chaired by Bob Katz (Digital Domain), with panelists Ian Dennis (Prism Sound), Andy Moorer (Sonic Solutions), MIke Story (Data Conversion Systems), Bob Stuart (once again!) and Daniel Weiss (Weiss Engineering). Glenn Zelniker (Z-Systems Audio Engineering) was scheduled, but illness prevented his attendance.
The members of this session are strongly interested in high sound quality, within the constraint of needing to make a living. Some of their thoughts:
• All agree that greater than 16-bits/48kHz is needed. For convenience, 24 bits is the maximum supported by the AES standard digital interface, and 96kHz is twice the audio-for-video rate. The maximum sound pressure level to produce is 120dB, and the related noise floor from a 20-bit word is inaudible to most listeners.
• There is some thought that 20 bits at 58kHz without noise shaping is sufficient for the consumer product, and even fewer bits could be used with noise shaping. Michael Gerzon was researching noise shaping and pre-emphasis for digital recording, and his results have demonstrated substantial improvement over the way pre-emphasis is implemented on CDs. Further study is required.
• The primary sonic benefit from sampling rates higher than 58kHz comes from reducing filter artifacts.
• Andy Moorer noted that it is dangerous to base a standard on available hardware (This is particularly valid, considering the phenomenal rate at which technology advances). There is a general feeling that with the dropping cost of computer memory and processing power, the DVD-Audio standard should be a minimum playback standard that allows for technological improvements.
Everyone Gets Into The Act
All of this activity has clarified some issues, and raised a lot of questions from within the groups directly involved and from others who are concerned, many taking the same positions as the Players:
• The industry needs to learn as much as possible about the technology before establishing a standard that might be substantially flawed. Everyone needs to remember that just as the CD is not a perfect medium, the DVD will also not solve all the problems and fulfill all the professional or consumer needs.
• The rationale behind some parameters of a standard is decidedly serendipitous. Dr. Kees Schouhamer Immink of Philips Research Labs is considered the Father of the CD. As a point of historical perspective, he recently said that the 44.1kHz sampling rate of the CD was dictated by the existence of Sony's PCM adapter (which others have said was based on the ability to use existent video recorders), and that the CD's size was kept near the diagonal dimension of the analog cassette because they felt the consumer wouldn't want anything larger. Immink put the DVD-Audio standardization effort partially in perspective when he pointed out that 1) the DVD physical specification is complete, while CD variations such as CD-ROM were "a very ad hoc solution," and 2) the CD was designed as an audio-only medium, but the "DVD is designed as a data disc, and therefore, it also allows video or audio." David Kawakami has also pointed out that the DVD-Audio specification development is a refinement of the DVD standard for this particular application, also noting that the DVD format itself is already fixed.
• How high the sampling rate needs to be is receiving a lot of conflicting discussion, even how to make the determination. For example, Andy Moorer and Glenn Zelniker feel that monophonic measurement masks some of the time resolution limits that binaural measurement clarifies. Many believe the problem is fundamentally based in the anomalous impact of anti-aliasing filters, and how much higher to make the sampling rate, and how complex to make the filters has to be further explored. In contrast, there are those who feel that current communication engineering theory is quite adequate for the task.
• The recording and production process certainly needs higher capabilities than the consumer playback medium. One possibility suggested is to use 24-bit/96kHz for recording and processing, and 20-bit/48kHz for consumer playback.
• Some industry experts have said that although higher bit rates might theoretically provide substantive improvement in lowered noise, distortion and detail resolution, the noise introduced by microphones, mike preamps, and other equipment generally masks the benefits of more than 16 bits.
• DVD players will require a digital audio output to permit external DSPs, probably from companies like Lexicon or Meridian, to decode the signal in a manner that will satisfy the audiophile.
• It is clear that current DVD players will not be able to decode all the capabilities of whatever DVD-Audio standard is established. However, if, as the ARA and others have suggested, DVD-Audio discs include the CD layer and the mandatory PCM- or AC-3-encoded bitstream, they will be playable, with the less-stellar audio quality and functions, on the millions of existing CD players and current DVD players. This will maximize the marketing potential while eliminating multiple inventory problems, letting consumers purchase a single disc and select the playback equipment, now or later, to provide the level of performance desired.
• Some experts question whether the Sony-Philips DSD system is sufficiently efficient and can guarantee sound quality as high as PCM encoding. Many involved in the standard definition process worry that the Sony-Philips DSD system will cause a rush to create and establish a standard that might not be a good one, and cause a format war. Thanks to the relatively low cost of computer processing and memory, it is possible to have both systems supported in the same player, just as DTS Digital Surround and Dolby Digital can coexist and run in the same processor, and avoid the format war. Everyone hopes that caution and thoroughness will win out, and that the process will take whatever time is needed to ensure a long-lasting high quality DVD-Audio standard.
• The prevailing opinion is that creating a single industry-wide standard is critical for DVD-Audio to have a rapid rate of acceptance and ultimate success as the music medium of choice.
• The DVD-Audio standard needs to be flexible enough to prevent its becoming prematurely obsolete and unable to meet the industry and consumer needs.
• The standard also needs to be defined enough to facilitate early use of the header data. For example, most of the 6 data bits out of each 14 on a CD are not used because they were not defined in the original standard.
• An open approach would be to standardize the data bitstream signal format, and let the data stream carry the codes, algorithm and software to load and run the decoder. This simplifies decoder design into a general purpose DSP, and eliminates obsolescence since newer codes come with newer discs, and older discs can still be played with their own software or benefit from the newer software downloaded from a previously-played disc. Some of the current digital film sound systems use a similar technique to automatically upgrade the playback system software.
• Divx (DIgital Video eXpress; www.divx.com), the new pay-per-viewing-period-with-purchase-option DVD format, is an added business complication that is independent of the DVD-Audio standard development process. It is viewed as either a hindrance or a benefit, depending on perspective. It is a hindrance to DVD acceptance because it is a change to a format assumed fixed by the consumer, making all current DVD players obsolete, and is perceived to force the end user to keep paying for a type of product he is used to buying only once (though that is not the actual case). This confuses the consumer and causes him to delay investing in the overall technology. On the other hand, some consider it a way to enhance inexpensive exploration of music, video or data they would not otherwise try outxspend a little to examine it once, then either pay to keep it, or throw it awayxno need to return it, as with rental video tapes. It is an interesting concept.
• To further complicate matters, some feel that those involved in DVD-Audio standardization are working with blinders onxpursuing only high-quality music reproduction (a small portion of the product delivered by the recording industry)xand need to consider other applications, like talking books, language lessons, convention session recordings, etc.xapplications for which the audio cassette is still used.
Progress!
On January 7, 1998, WG-4 submitted a draft DVD-Audio specification to their own members, to the original DVD Forum members, and to the ISC member organizations for consideration, seeking feedback [Why it was not submitted to a broader audience is not known].
Quoting from the press release [comments by Bike H. Suzuki, chairman of the WG-4 DVD Audio Working Group]:
"The WG-4 recognizes that the music industry's top priority is copy protection." Suzuki added, "For this reason, we believe the final format design must be capable of accommodating new secure protection technology such as watermarking, or embedded data technology.
"In contrast to the current DVD format, the audio specifications utilize the disc capacity by emphasizing improved next generation digital sound quality rather than the playback of 135 minutes of video. When the specifications are finalized, DVD-Audio will join DVD-Video and DVD-Rom as a compatible family of formats.
"The draft specifications are the result of extensive discussions over the last two years. In addition to the views of the ten WG-4 companies of the Consortium, many outside interests expressed views that were taken into consideration.
"In particular, the International Steering Committee (ISC), representing the major music companies and their trade associations, proposed requirements which were recognized through a series of 14 meetings between WG-4 and ISC representatives. The draft specifications describe in detail how the (13) ISC format requirements will be satisfied."
Mr. Suzuki's comments seem to make the WG-4's priorities quite clear.
The draft specification delineates a flexible standard that requires at least a scalable, uncompressed 2-or-more-channel PCM-encoded program. It permits additional multichannel versions of the program without specifying the format, but allowing (without naming) Sony/Philips' DSD, Dolby Digital, DTS Digital Surround and MPEG.
The PCM-encoded signal may use sampling rates of 44.1, 48, 88.2, 96, 176.4, or 192kHz(48 and 96kHz are already part of the DVD-video specifications); and digital word lengths of up to 24 bits(16, 20 and 24 bit words are also already in the DVD video specs).
Compression of the PCM signal isn't endorsed, but WG-4 is still considering the possibility.
For the multichannel signal, the draft spec allows a variety of sampling rates and word lengths, such as 5-channel/96kHz/24-bit, as well as mixed coding parameters such as L-C-R in 96kHz/20-bit with the surround channels in 48kHz/24-bit (to lengthen the playing time).
The draft spec also allows a CD Red-Book-complaint layer. Comments by Jordan Rost, Warner Music Group's Senior Vice President of new technology, that the music industry isn't particularly concerned with the lack of a mandatory CD layer, imply that the music industry expects (wants?) the CD to be replaced by the DVD.
WG-4 hopes the final specification can be issued by the end of May 1998, and that compliant DVD players could be on the market by Spring, 1999.
Progress???
This is a very open specification that allows musicians, engineers and producers to make their own choices, and accommodates foreseen technological improvementsxboth factors appreciated by recording professional.
On the other hand, these same creative professionals are disquieted not only by the dynamic state of DVD-Audio development, but by the questionable prospects for large-scale success of the DVD outside of the computer marketplace. Consider:
1. Many consumers see no benefit from the DVD, since it costs more than a VCR and video tapes, it can't yet record, and VHS-quality is quite adequate for time shifting a sitcom or recording a movie off broadcast television or cable. This alone implies a limited market.
2. DVD is really a home theatre (video-based) mediumxit is for those of us who want high quality video and audio, and are willing to pay for it, especially since it seems to be less costly than LaserDisc players and LaserDiscs. However, many of us are still waiting for the players to include DTS recognition, and there are very few players offering the necessary component video outputs and shiftable black level (needed in some high end systems for proper ISF calibration). Although growing explosively, the home theatre market is a relatively small, upscale marketxafter all, it costs a lot more for a decent large-screen video display, a digital surround processor and 5.1 channels of amplifiers and speakers than for a fairly good-looking TV set and 2-channel stereo.
3. Add the conflict caused by the late introduction of the Divx-DVD concept, and it's no wonder the crystal balls are cloudy, and the audio creators hesitant.
4. Will enough audiophiles buy sufficient numbers of DVD-Audio-compliant players and DVDs to help each music creator justify spending more than one hundred thousand dollars investment capital to enable his recording and production system to produce multi-channel audiophile-grade music -only DVD master recordings? And will they also be Divx-encoded? Many of these people remember quad, and aren't sure how the multiple channels (5.1, 6.0 vertical recording hall ambiencexa nice beneficial effect, but not enough by itself to economically warrant the expense or effort.
5. Will enough audiophiles, who typically have spent a lot of money on their 2-channel systems, be willing to spend more than their initial investment to add a DSP and at least 3.1 more channels of amplifiers and speakers? If not, it is certainly not worth the recording artist adding multichannel DVDs, to his production facility; yet, without multichannel DVDs, will the market be anything larger than invisible? It seems the DVD-Audio-only marketplace could be very small. Remember, Telarc, Mobile Fidelity and Sheffield are not big companies.
6. Will the DVD player manufacturers, some of which are also producers of music software, cooperate enough that all players will support all the formats that exist and might soon arise, or only support the format they produce? (We have all seen uncompromising corporate behavior.) If not, and if the audiophile-quality recording facility buys into the wrong technology, it will probably go bankrupt.
At the same time, such an open standard means that either:
1. Separate machines will be required to play back DVDs encoded in different formats,
2. Each machine must include the software to play back ALL of the different formats (hopefully, in this case, the manufacturer could offer a low-cost DVD-ROM which, when played, will automatically upgrade all the software stored in the player), or
3. The player must include a somewhat more general DSP, with automatic detection and activation of the appropriate algorithm, sampling rate and word length for proper playback. In this case, the algorithm and playback software could be included in the header of the DVD, then automatically downloaded and run when the disc is played (similar to extracting automatically-executing computer programs from a compressed file). This enables each disc to carry the software most appropriate to its format, and allows the consumer to take advantage of future algorithmic and software improvements without having to purchase a new player; plus, the manufacturer won't have to deal with upgrading ROMs and will not have to include the extra-cost memory to hold all the software.
Audio is a business. What the consumer will purchase, and for how much, sets the terms of the marketplace. If the creative professionals encounter a market much smaller than they predict, and they overextend their finances adding DVD-Audio production capabilities, they will go out of business, and we all lose a source of quality audio, even if it isn't in the latest format.
Postscript
Talk about a quagmire!
Are you befuddled yet? Overwhelmed? I am, and I am also concerned. This is a rare opportunity to try to define what today could pass for a long term standard in the consumer audio world. Many of us wonder how well these efforts will succeed in serving the consumer. Consumers wonder just how much their needs and wants, not just their money, are being considered.
Listen carefully for the sound of our sonic future.
Footnote - An amazingly thorough DVD web site is "http://www.unik.no/~robert/hifi/dvd".
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