From wlrc@riker.neoucom.edu Wed Mar 1 12:45:08 EST 1995 Article: 26258 of alt.video.laserdisc Newsgroups: rec.video,alt.video.laserdisc,rec.audio.tech Path: casaba.srv.cs.cmu.edu!rochester!udel!gatech!newsfeed.pitt.edu!godot.cc.duq.edu!news.duke.edu!eff!neoucom.edu!wlrc From: wlrc@riker.neoucom.edu (William R. Cruce) Subject: FAQ: Dolby AC-3, DTS & 5.1 channel laserdisc surround sound Message-ID: Supersedes: Organization: Northeastern Ohio Universities College of Medicine Date: Wed, 1 Mar 1995 16:03:27 GMT Expires: Wed, 29 Mar 1995 14:00:05 GMT Lines: 276 Xref: economic.mess.cs.cmu.edu rec.video:77594 alt.video.laserdisc:26258 rec.audio.tech:9967 AC-3_251.FAQ FAQ: Dolby AC-3, DTS & 5.1 channel laserdisc surround sound Version 2.51, 03-01-95. Copyright 1995 by William L.R. Cruce WHAT IS 5.1 CHANNEL SOUND? It is a system for delivering 5 discrete full-bandwidth surround sound channels (left front, center, right front, left rear, right rear) and a limited bandwidth "effects" or subwoofer channel (the 0.1 channel). There is a SMPTE standard for it covering theatrical motion pictures. Although mastering movie soundtracks for 5.1 channel sound is still in its infancy, it is hoped that the full-bandwidth channels will take advantage of the bass normally in music and general sounds and that the effects channel will be reserved for extra bass to be added for impact, e.g. fistfights, Tyranosaur foot stomping. There is considerable interest in the music industry for using a 5.1 channel system to deliver music in surround sound. WHAT IS AC-3 AND DSD? AC-3 is Dolby's name for the algorithm or codec they use in DSD (Dolby Surround Digital) to compress 5.1 channels into a small digital space. They have used it for several years to encode 5.1 channels of digital sound on theatrical film (320 kilobytes/second, kbs) and now they are using it, in collaboration with Pioneer, to place 5.1 channels of digital sound in the frequency space formerly occupied by the right analog channel on laserdisc (384 kbs). AC-3 is a clever and sophisticated perceptual coding system which achieves an average 9:1 or 10:1 compression ratio. It is possible that AC-3 may be adopted as the compression algorithm for the sound in HDTV, for satellite transmissions, and for the proposed Digital Video Discs. The standard stereo digital sound channels on a laserdisc are left alone by DSD/AC-3 and may contain the usual Dolby matrixed surround sound. Thus Dolby/Pioneer claim that their system can be added to new laserdiscs without confusing consumers or disrupting the laserdisc market; there will be no need for a double inventory of disc titles. The only laserdisc player owners who will notice are those who still have old analog-only players and it is claimed that they are a very small part of the market (Laserdisc players with digital sound appeared in the mid 1980's and the last analog-only one was made in 1989). Dolby hopes to repeat the method by which they quietly introduced Dolby Surround Sound into software for the home market; it was carried over from movie soundtracks to stereo soundtracks on laserdisc and videotape but consumers weren't forced to buy any new equipment until they wanted to hear the new sound. It is probably the potential for not disrupting the market and for quietly building an inventory of software that convinced the LaserDisc Association, which sets standards for the the LaserDisc system, to officially sanction Dolby's AC-3 format. This means that DSD AC-3 discs may carry the "LaserDisc" logo. WHAT EQUIPMENT DO I NEED TO HEAR DSD/AC-3 LASERDISC SOUND? (1.1) You will need a laserdisc player with an AC-3 radio frequency (RF) output for connection to an outboard DSD/AC-3 demodulator/decoder. Runco makes a high end model, the LJR II, which was the first to have this output (one of the requirements for THX LD player certification, of which this is the first). It costs about $4000-5000. Existing players may be modified to have an AC-3 RF output for under $100 (parts cost is less than $5) by a local repair shops or mail-order modifiers (no one has announced plans to do this, as yet). Laserdisc players with AC- 3/RF outputs should cost no more than current ones as the parts involved cost only a few dollars. (1.2) At the January WCES, Pioneer announced their new '95 line of AC-3 ready laserdisc players. All have an RCA connector in the back labeled "AC-3 RF". Four models (MSRP, street date) were announced: CLD-D704 ($1200, April), CLD-D604 ($1035, April), CLD-D504 ($660, March), CLD-S304 ($535, April). Street prices will typically be a few hundred less. The 304 is a basic model. The 504 adds 2-side play. The 604 adds digital field store. The 704 adds somewhat better performance, variable digital noise reduction, coaxial digital out (making it also suitable for DTS decoding, see below). The 304, 504, and 604 will include some limited Karoke functions. A successor to the Elite CLD-97 (currently one of the best performing laserdisc players available) with AC-3 output will probably be announced later in the year and will probably carry the designation CLD-99. No more information was available about this model. (2) You will need an outboard box which contains a demodulator for the RF signal and an AC-3 decoder. A half dozen manufacturers showed systems with DSD AC-3 capability at the January 1995 WCES in Las Vegas (ADA, EAD, Denon, Kenwood, Perreaux, Pioneer, Yamaha). Some were stand alone surround sound decoders, some were preamp/control units, and some were complete receivers. Per Dolby requirements, all will be able to perform standard Dolby Pro Logic decoding from a stereo signal with matrixed surround sound. Most of the AC-3 decoders and receivers announced at WCES were expensive, i.e. $1000-6000. Presumably, once manufacturing ramps up and the digital signal processing (DSP) ICs for doing AC-3 become common, prices will come down. Currently, only ZORAN makes the ICs, but Texas Instruments and Motorola are reported to be considering it. (3) The DSD/AC-3 system produces 5 full bandwidth (20 Hz-20 KHz, +/- 0.5 dB, -3 dB at 3 Hz & 20.3 kHz) signals and one limited bandwidth (20 Hz-120 Hz, -3 dB at 3 & 121 Hz) subwoofer or effects channel. To take full advantage of it you will need 5 full-range speakers, 5 amplifier channels, and either a powered subwoofer or a subwoofer plus mono amp. If you currently have stand alone (as opposed to integrated in a receiver) surround sound amps they should work fine. Receivers or integrated amps may be used provided they have separate discrete inputs for each internal amp. Your current speakers may be used though eventually you may wish to upgrade the surround speakers and center speaker to be the full frequency range that the 5.1 channel system supports. Although THX argues that their specification for dipole surround speakers to diffuse the sound is still valid, most of us would prefer to use speakers that will take advantage of the discrete nature of the surround sound in a 5.1 channel system. HOW DOES DSD/AC-3 SOUND? Demos at WCES almost all used the same laserdisc player, the Runco LJR II, the same demodulator/ ZORAN decoder circuitry provided by Dolby, and the same Pioneer demo laserdisc with cuts from TRUE LIES, THE MASK, SPEED, and CLEAR & PRESENT DANGER. The differences in sound seemed to be well correlated with the audio system involved. Pioneer's sounded awful and the ones from Denon/Kef and Yamaha were not impressive. Kenwood's malfunctioned and was not shown. The Perreaux/Monitor Audio was encouraging, the EAD even better. But the most spectacular demo was that by ADA, using their $29,000 tubed decoder (with ZORAN AC-3 IC circuitry inserted). They were able to seamlessly switch between between any combination of an analog Dolby Pro Logic decoder, a THX decoder, a DSD/AC-3 decoder, M&K THX approved speakers (rear dipoles), non-THX Tannoy speakers (rears direct like front) and less expensive and more expensive ADA amps. Two things were significant about the ADA setup. (a) the system levels appeared to have been set up correctly and (b) they could instantly switch between AC-3 decoding and standard Pro Logic or THX decoding. I don't believe the $29,000 decoder (with 15 tubes) was a significant factor; ADA also makes a very fine decoder in the several thousand dollar class. When the standard demo was over we had them run the clips from TRUE LIES and THE MASK again in both AC-3 and Pro Logic modes. We had by now heard and seen these clips 5 times previously and a sixth time just before in this room. We were familiar with them to the point of pain. The result? AC-3 has incredible directional capabilities. For example, in the TRUE LIES scene where Harrier Jets are attacking the terrorist convoy on the bridge and the terrorists fire a ground-to-air missle at a jet, the missile quite dramatically moves from front right to rear left. It does so with such ferocity that your hair is almost singed. In the ADA demo the Pro Logic mode could not accomplish this (nor can it on my home system with a Lexicon CP-3+ Pro Logic decoder). As for the overall sound, there was nothing distinctly distorted or unpleasant about the AC-3 sound. Caveat: none of the tests had subtle or delicate sound, either music or sound effects, where I would listen for problems. None of the tests had simultaneous transients in all 6 channels, a condition which would be a worst case for AC-3; but this is a condition which rarely occurs in any movie soundtrack. My current thoughts on AC-3 are that it *does not* not sound as bad as I had feared (based on the high degree of compression it uses) and it *does* offer more dramatic spatial effects and directionality than our current Pro Logic systems. I will await further testing in my own home setup (decoders from EAD are just now being sent to a few reviewers; other decoders are expected shortly) before stating anthing more conclusive. WHAT IS DTS SOUND? It is supposed to be a competing format for 5.1 channel sound on laserdiscs. Digital Theater Systems (DTS), which makes a widely used digital system for theatrical films, has announced that they will have a format for digital 5.1 channel sound on laserdisc which is different from that of Dolby/Pioneer. They will compress the 5.1 channels into the space used by the current stereo digital soundtracks (1.44 Mbs) for a compression ratio of about 3:1. Since their proposed system would require less compression than Dolby's, people have supposed it would sound better. But since the algorithm they use for compression is quite different from Dolby's, the differences in sound are not so simple to predict. (In A/B comparisons I have heard between the two theatrical systems in Lightstorm's Los Angeles screening room there was little difference. I thought AC-3 had a slight edge in the superior way it handled the subwoofer channel.) The proposed DTS system would put its signal out via the digital connector of a laserdisc player. Most higher priced LD players have a separate digital output for an outboard DAC box, so if you have one of these a new player would not be needed. You would still require an outboard DTS decoder. Manufacturers could conceivably include both AC-3 and DTS decoding capability in their boxes. Many have said they would, IF THEY HAD ANYTHING CONCRETE FROM DTS ABOUT HOW TO DO IT. But, as of WCES time, they had no information from DTS. DTS points out that their discs would be compatible with *all* laserdisc players because the analog tracks would remain in stereo and could carry traditional matrixed Dolby Surround Sound. But they have a major marketing problem in that many consumers have been drawn to the LD format partly for the CD-like digital sound and may not wish to take what would be perceived as a step backward to analog sound (if they don't have a DTS decoder). Consumers might be confused or irritated when they start up a laserdisc only to get "noise" from the digital channels (all players default to the digital channels on startup). Thus there is the likelyhood that consumers and retailers would be faced with a double inventory of discs: those with standard digital channels and those with DTS digital channels. Since DTS has not been approved by the LaserDisc Association, DTS discs may not carry the "LaserDisc" logo. Pioneer has said they would press discs for DTS in their plants just as they would for any paying customer, but they would not be official "LaserDiscs." A more significant problem is that DTS has yet to openly demonstrate a working laserdisc system. They had nothing at the WCES '95 and they failed to provide a promised demo for The Perfect Vision writers in LA the week after WCES. They have decoders, used in their theatrical systems and they have been demonstrating the "transparency" of these decoders on music to some people in the audio industry (reported in the last several issues of Widescreen Review). If they have a prototype laserdisc system now they are more than a year behind Dolby/Pioneer. Even if they do eventually produce discs and decoders they will not be a major factor in the laserdisc market. WHAT FILM TITLES WILL AVAILABLE ON LASERDISC WITH AC-3 FORMAT? As of mid February, 1995, CLEAR & PRESENT DANGER and TRUE LIES have been released. Officially announced are STARGATE and FORREST GUMP. Planned, but not announced or available (i.e. subject to change) are STAR TREK GENERATIONS, DROP ZONE, TOP GUN (WS), U2 RATTLE & HUM, and CONGO. Pioneer says there will be about 20 AC-3 titles by late summer, perhaps 50 by the end of the year. These will be new laserdisc releases as well as re- releases of selected films which were mastered with 6 or more discrete digital sound channels. WHAT ABOUT DTS TITLES? As of mid February, 1995, no titles have been announced for DTS. WILL JURASSIC PARK BE RE-RELEASED AGAIN IN EITHER FORMAT? A re-release of Jurassic Park with DTS sound would seem an obvious candidate, since Steven Spielberg is an investor in DTS, but this is purely speculative. It is far more likely that Jurassic Park will be released in DSD AC-3 sound to take advantage of the momentum developing in both hardware and software areas. WHERE CAN I FIND OUT MORE ABOUT DSD, AC-3, DTS, & 5.1 CHANNEL SOUND ? The best way to keep up with new title announcements and late breaking news will be to watch your favorite on-line home theater discussion group, e.g. on the internet, the news group, which seems to be the defacto group for home theater. There also has been discussion of DSD, AC-3, DTS, and 5.1 channel surround sound on laserdiscs in , and in and . An email query to Eileen Turri (ert@dolby.com) of Dolby Laboratories in San Francisco will bring you a packet of white papers and information by snail mail. I am not currently aware of any similar information available from DTS but will try to include such in future versions of this FAQ, if that format ever becomes real. -- Bill Cruce wlrc@neoucom.edu ===================================================== from STAY TUNED: "666 channel, 44 inch, 900 line resolution, 3-way expanded matrix Dolby Stereo TV. Some people would give their souls for a system like this."