The Laserdisc FAQ

by Henrik "Leopold" Herranen

I) Introduction to Laserdisc

1.1 What is LD?

From Bob Niland's (rjn@csn.org) LD#01: ..but it can't even record?

LD stands for LaserDisc, the industry-wide term for consumer laser video. During its life, the format has also been known as LV (LaserVision) and CDV (Compact Disc Video). The players are also sometimes referred to as VDPs (Video Disc Players) and Sony calls them MDPs.

LD was first demonstrated by Philips and MCA in 1972, and has been on the market since 1978, or about as long as VCR and six years longer than CD. There are more than 1 million players in home use in the U.S. (compared to 85 million VCRs), and more than 4 million in Japan (10 percent of households there). The U.S. installed base is increasing at more than 15,000 units per month.

1.2 What are the advantages/disadvantages of the laserdisc format?

In real short, a bright and detailed (as opposed to murky and grainy VHS) picture, sound that sounds like a CD on new movies and clearer than you ever thought it could be on old ones, and the ability to blow your friends away with a snazzy picture and booming sound that make VHS look like, in James Cameron's phrase, "crap-vision."

LD advantages

• Picture quality. With the exception of DVD, Laserdiscs are by far the best-looking and sounding home video system available. And although NTSC is a inferior TV system compared to PAL, PAL broadcasts almost never look as good as the better NTSC LDs. There is more resolution, and less noise and time-base errors compared to other analog home video systems.
  
  
• Audio quality. The quality of stereo digital sound on LDs is exactly as on CDs and 5.1 channel Dolby Digital can go far beyond any 2-channel audio reproduction format.
  
  
• Letterboxed editions. It is fairly easy to get your favourite movie in the theatrical aspect ratio on LDs. This was my final reason to buy a LD player.
  
  
• Special editions. Because of the extraordinary capabilities of LDs (multiple audio channels, still-frame archives), there are special editions of films that gives you real in-depth information about your favourite movies.
  
  
• Random access.
  
  
• Full still-frame capability on CAV discs, and still-field with some players on CLV discs.
  
  
• Durability. LDs are read optically. They will last forever if you treat them well.
  
  
• Cover art. The covers look much nicer than VHS covers because they are bigger.
  
  
• With few high-end exceptions, LD players can also play CDs.
  
  

LD disadvantages

• You cannot record. Laserdiscs are a strict playback only media.
  
  
• The sideflipping blues. As a CLV disc can only hold up to 60 minutes per side (64 in PAL) and a CAV disc can only have 30 minutes (36 in PAL), you have to turn the disc at least once for every movie if you don't have a double-sided player.
  
  
• Price. Compared to VHS, LDs are more expensive to manufacture and a movie on LD does usually cost more than on VHS. The reason to this is partly because of the media and partly because the masters are usually given a much better treatment. Without good masters LDs would look just as crappy as VHS.
  
  
• Availability. Especially here in Finland laserdiscs are hard to find. In practise they have to be ordered from the USA, which is always little more troublesome than going to the nearest supermarket. Fortunately these days several LD retailers have Internet access and www pages.
  
  
• No subtitles. If you are not lucky enough to understand English fluently, you won't get much out of LDs. There are no laserdiscs with, say, Finnish subtitles. It is technically easy to have different language subtitles on PAL LDs as teletext pages, but unfortunately the smaller language groups are never included.
  
  
• Fewer rental outlets.
  
  
• Title availability lower and more unpredictable than VHS.
  
  
• Laser rot. In some pressings there are discs that detoriate as time goes by. This may be caused by bad glue when gluing the two disc sides together or air bubbles being left inside the disc, which will cause the aluminium layer to oxidize.
  
  
• All the best pressings are NTSC. This means that in a PAL country you need an NTSC capable player and TV set to see the movies correctly and you can't record the discs on tapes.
  
  
• The picture on the discs are in the composite domain. This is the same as with broadcast television, but nevertheless it makes it hard for a television to decide which parts of the picture are luminance (black and white) and which parts are chrominance (colour) information. Good comb filters are needed to do the job.
  
  
• The players may have high mechanical noise.
  
  
• The discs are big, and a bit hard to handle.

2. ADVANTAGES

2.1 Is it true laserdiscs will outlive me?

From Bob Niland's (rjn@csn.org) LD#01: ..but it can't even record?

As with CD, and unlike tape formats, LD is a non-contact medium during play. There should be no wear in normal use, even if you freeze a single frame on screen for hours.

The theoretical shelf life of an LD that is "properly manufactured" and properly stored is the same as for CD -- essentially unknown, and possibly longer than the photographic negatives/prints from which the disc was made. There are no known deterioration modes for properly made and stored discs.

Contrast this with an optimistic shelf-life of 20 years for magnetic tapes of all kinds (less if used often). Tapes have several known deterioration modes: print-thru, binder breakdown, base stretch, and physical abrasion wear and signal loss due to external fields (magnetized VCR components, speaker magnets, CRT deflection coils, etc.)

Note the emphasis on "properly made disc" above. I have separate articles available on LD quality (LD#04), identifying LD defects (LD#17) and the interpretation of LD mint marks (i.e. who cast or pressed it, LD#09).

Discs do fail on the shelf, and experience other manufacturing defects more immediately evident. I have had several discs with "laser rot". I have also purchased discs with contaminants under the acrylic.

The initial defect rate for LDs is lower than for pre-recorded VCR tapes. The rate seems to be slightly higher for LDs (about 2%) than for CDs (which are about 1%).

2.2 Is the picture really better than my VCR?

Pioneer pitches LD as "60% sharper" than VHS. LD image quality is roughly comparable to standard 16mm film, VHS is roughly comparable to 8mm film. There are no home video formats comparable to 35mm or 70mm film.

The pulse-FM data structure on an LD (unlike ordinary VHS/Beta), is defined to hold all the information present in the composite video signal. Depending on source material and the transfer to disc, LD is above live TV broadcast quality: For NTSC, this is 425 TVL (luminance lines horizontally for 3/4 of the screen width) and about 482 scan lines, compared to 330x482 for broadcast. For PAL, the numbers are 450x560 and 400x560, respectively.

Compare this to 240x482 for good VHS (recorded, pre-recorded is probably less). Only recently have Super-VHS approached LD capability, and ED-Beta has gone even further with its resolution of 525x482. Of course, pre-recorded material is not widely available in these VCR formats. Even using S-VHS/ED-Beta to tape off-air still only reaches the 330x482 of the broadcast signal (400x560 in PAL countries).

Compared to LD, all consumer tape formats also fall short in time-base stability, chroma resolution, video noise and audio fidelity.

Although the video signal-to-noise ratio (s/n) appears to be about the same for LD and VCR hardware, it is probably not the same for mass-produced pre-recorded material. The LD process (casting or stamping) does not degrade the signal from master to copy. The tape process, magnetic contact printing, does.

All LD players have time-base-correction; mechanical, optical, analog electronic or digital. TBC eliminates the horizontal line jitter and color errors common on tape.

2.3 What about the sound quality?

Laserdiscs can currently have three different kind of sound. These different sound schemes are gone though in this chapter.

All sound combinations are not possible. The possible combinations are:

NTSC discs:

• 2 analog channels (last discs like this were made in the 80's)
• 2 analog channels + 2 uncompressed digital channels
• 1 analog channel + 2 uncompressed digital channels + 5.1 Dolby Digital channels
• 2 analog channels + 5.1 DTS channels

PAL discs:

• 2 analog channels (last discs like this were made in the 80's)
• 2 uncompressed digital channels

2.3.1 Analog channels

This is the old way. Originally LDs had only 2 analog audio channels, that were considered of high quality those days. However, especially the right audio channel has problems with loud high voices, and it may break in total distortion.

Most newer discs have a noise reduction called CX on the analog audio channels. CX noise reduction can be turned on and off anytime on a disc by the player (controlled by the disc itself). On Dolby Digital discs, or on discs that have separate contents for the left and right analog channel, CX can't be used (without problems).

The audio might be considered subjectively little worse than VHS Hi-Fi.

On NTSC discs, analog audio channels are nowadays often used to carry extra information, like commentary soundtracks. This can't be done with PAL discs, where analog and uncompressed digital channels are mutually exclusive. With NTSC discs, the right analog sound channel can be sacrificed to give the consumer Dolby Digital.

The last players with analog-only sound were made in 1989.

2.3.2 Uncompressed digital channels, or PCM channels

The 2 uncompressed PCM-encoded digital channels follow the same high specs as CDs: a sample rate of 44.1 kHz (actually 44056 Hz for NTSC) and 16 bits / channel keeps the sound as good as it can be given there are only two separate channels. Thus, the sound quality easily surpasses that of any home VCR of today.

The uncompressed digital channels are the main audio reproduction system of today. Along with a Dolby Surround Pro-Logic decoder you may get a 4-channel output with 3 channels (front left, front center, front right) of full bandwidth (5-20,000 Hz) and 1 channel (back) with limited bandwidth (100-7000 Hz). Although only a limited amount of panning is allowed and some effects can't be done at all, the beauty in Pro-Logic lies into its ability to encode 4-channel sound on any stereo media.

PAL LDs can only have either analog or uncompressed digital audio.

Uncompressed digital audio has been used for 10 years now, and all new LDs have been with digital sound for years now. The last NTSC LDs without digital sound were done in the late 80's.

2.3.3 Dolby Digital a.k.a. AC-3, or compressed digital channels

Dolby Digital, which used to be called Dolby AC-3, is a new sound system. LDs utilizing this audio format have been manufactured since the beginning of 1995. At this point most new players have an RF Dolby Digital output, and many external decoders and integrated amplifiers that can decode the information. Adding a Dolby Digital RF output to practically any LD player is trivial (See the Hardware section), and as Dolby Digital will be the sound system for both American HDTV and DVD, even more receivers are very soon to be reality.

DD replaces the right analog audio channel of NTSC LDs with a 384 kbit/s data stream that can be decoded to 5+1 channels of sound. This system is sometimes called a 5.1 channel sound system, which means that 5 channels (front left, front center, front right, back right, back left) are of full bandwidth (5-20,000 Hz), while the 6th channel is a special subwoofer channel (2-120 Hz) that will be used only when the movie maker want to have heavy bass.

The DD track is heavily compressed: while an uncompressed digital channel use some 700 kbits/s, a DD full bandwidth channel can only use some 75 kbits/s (average). However, because perceptual coding is used and most of the time almost all of the sound energy is transmitted to the center channel, the actual compression ratio is most of the time nearer 3:1 than the presented 10:1 ratio. During my early tests (Crimson Tide, Star Trek Generations, Die Hard), I have been less than 10 times able to hear any artifacts that could be caused by compression.

With DD discs and non-DD LD players, you will hear static noise in the right analog channel. If your player is an old analog-only player, you have to switch to the left channel and listen to the film in mono sound.

DD is totally different from anything previously available at the home video market. It is a major breakthrough in home theatre audio reproduction, and to my opinion the jump from plain stereo to Dolby Surround Pro-Logic is smaller than the jump from Pro-Logic to DD.

DD is not available on PAL discs.

2.3.3 DTS

DTS is a new sound system for NTSC LD players, which offers much of the same functionality as Dolby Digital, but with less compression.

DTS is not an official part of the LD standard, but DTS discs can still be played with any NTSC laserdisc player.

DTS occupies the space reserved for digital audio on normal LDs, using a data bitrate of approximately 1.4 Mbits/s. In practise this means that those people who buy DTS discs but don't own DTS decoders, will only be able to listen to the analog soundtrack.

To listen to a DTS disc, one needs a laserdisc player with a PCM digital output, a DTS decoder, and, of course, enough amplifier power and speakers to carry the 5.1 channels.

2.4 What cool features can I expect out of laserdisc players?

From Timm Doolen

Unlike tape formats, laserdisc is not a linear format. Like CD, you can go to the exact position on the disc you want. On CLV, you can position the disc to the nearest second. On CAV, you can seek to the frame number.

Most discs also have chapter marks, similar to tracks on a CD. Seeking frames/chapters is extremely quick on CAV discs because the speed of the disc does not have to change. Seeking time/chapters on CLV discs depends on the distance between the starting and end points, but never takes more than four to six seconds. Definitely faster than any rewind or fast forward on a VCR.

All players and discs can pause and search forward and back. Unlike VCR, there is no media or player wear when this is done.

CAV discs can also play forward and backward at variable speeds, from 1/90 normal speed to 10 times normal speed. Single-frame-step forward and backward is also available. Some newer players have a "jog wheel" that allows variable speed slow/fast motion. On most good pressings, the still-frame has the same resolution as the moving image, unlike VCR which often has blurring. A CAV LD can store 54,000 individual still images per side. The more expensive players can also freeze-field on CLV discs.

2.5 Can I play CDs on a laserdisc player?

From Timm Doolen

Yes. All current all LD players except a few high-end units can play 5-inch audio CDs. They are not usually as high quality as comparably priced CD players and often do not have as many high-end features, but they are not bad CD players. Some players have separate drives to spin audio-only CDs.

3. DISADVANTAGES

3.1 Can I record onto a laserdisc?

Excerpted from Bob Niland's (rjn@csn.org) LD#01 Revised: 04 Jul 94

No. Nor with CDs and LPs. Even if an economical recording LD machine is ever introduced, it is too late for LDs to dominate the video market the way that VCRs have. In audio, if you want quality playback, you get a CD or LP player. If you want to record, get a cassette or DAT deck.

The typical LD owner is likely to have both a VCR and an LD. Lack of recording is really a non-issue as the LD product is currently positioned.

3.2 Do LD players cost more than my VCR?

Excerpted from Bob Niland's (rjn@csn.org) LD#01: Revised: 04 Jul 94

New LD players run from $300 (discounted) to $3,500. You can get a VCR for under $200. If you are concerned about features, the prices of comparable LDs and VCRs are about the same.

You can get a used player from $100 up. The only significant missing feature on pre-1987 players is digital sound. The video performance appears to equal Pioneer's current low-end machine (CLD-S201). Conventional wisdom in the LD world says to avoid players prior to the VP-1000 (circa 1981).

Having once bought a used VCR, I would not do that again (worn out head). An LD player seems less prone to wear, and even if it doesn't work properly, at least it won't eat your media (as long as you remember to remove that pesky shipping screw :-).

3.3 Can I rent laserdiscs?

Excerpted from Bob Niland's (rjn@csn.org) LD#01: Revised: 04 Jul 94

Unless you live in a major market (and in North America), you may have trouble finding a rental outlet. There are reportedly some 5,000 LD stores in the U.S., including a few chains, and over a dozen national mail-order sources.

If you are renting for auditioning of the program material, rather than for routine viewing, this is not a big deal. Rent tapes and buy discs. Or simply borrow discs.

3.4 I've never seen a copy of my favorite movie on laserdisc but it's been out on VHS tape for years. Why?

From Timm Doolen

Although the list of titles available on LD grows every day, several popular titles have never been in print or were available years ago, but are no longer in print (e.g. several of the Disney animated movies, which are usually not available on VHS either). The lack of software is usually cited by laserdisc opponents as one of the reasons to not get into LD. But the list of titles is very rich, and with more consumers and consumer pressure, more titles will be released on LD. What's amazing is how many titles there are to choose from considering the limited number of consumers. Personally, unless I win the lottery, I'll never be able to purchase all the titles I want to own, because the labels are producing them faster than I can buy them. So I usually don't worry about hard-to-find titles, because I know sooner or later the labels will release it if they can make some money off of it. In the meantime, my want list of released titles constantly outgrows my ability to purchase those titles. However, there is some sort of cosmic law (you might call it a corollary to Murphy's Law) that no matter when you start collecting LDs, at least one of your top five favorite movies will either be out-of-print or never released.

There's also imports....

In some cases, if a title is not available in domestic release, you may be able to find it as an import. Japanese LDs may have modified contents. Japanese moviegoers are more critical than Americans, and insist on original-language presentation, rather than dubbing. So unless the disc is widescreen, the Kanji subtitles may appear on-screen and in-picture.

An accurate Japanese LD catalog is required to know for sure. Refer to LD#02 for more information on imported LDs.

Also, Japanese films censor some types of nudity acceptable in U.S. [R] rated films. THX-1138, George Lucas' first film, available on disc only in Japan until 1992, has flesh-colored airbushing. There are no uncensored [X] or [NC-17] American films at all in Japan. However, there's a huge market over there for X-rated anime.

3.5 How come when I watch a laserdisc, I have to flip the disc over?

From: Timm Doolen

CLV discs can store 60 minutes per side (64 for PAL discs), CAV allows 30 minutes per side (36 for PAL), requiring a side change at the end of each side. This is more of annoyance to some than others, and is a definite reminder that you are not watching a movie in the theater. The CAV version of Ben Hur requires 7 disc changes. Disc changes take at least several seconds, because the disc has to come to a complete stop and then start spinning again (whether you flip it by hand or have a multi-side player), each process taking at least two to three seconds.

In recent years, two-side players have become more and more affordable, allowing you to watch up to two hours uninterrupted on CLV discs, which covers a large percentage of movies.

4 OTHER DIFFERENCE BETWEEN LASERDISC AND VHS

4.1 What are those black bars at the top and bottom of my screen?

From Timm Doolen & Michael Gebert (MGMax1919@aol.com)

For a detailed look at aspect ratios, look in section 14 of this FAQ. What follows is a nutshell explanation of letterboxing and aspect ratios.

The original aspect ratio of films from the beginning of the century to the early 1950s was approx 4:3 or 1.37:1. When television came along in the '40s it modeled its ratio after this number. When television started becoming popular, the film industry responded by introducing wider and wider pictures to the audience through various means, including wider film gauges such as 70MM, multiple projectors (as with Cinerama), and most commonly today, anamorphic projection, which uses special lenses to squeeze a wider image onto 35MM film. Aspect ratios for movies in the 50's and early 60's ranged from 1.37:1 all the way out to 2.8:1 for Cinerama.

By the mid to late '60s, most of the thunder of widescreen was over and many in the industry went back to shooting movies on flat 35mm film (non-anamorphic) and matting the upper and lower portions of the image to give about a 1.85:1 image.

When these films were transferred to another format to be shown on TV, you had to do one of three things: lose part of the image to cropping, letterbox the image so it would fit inside the tube or squeeze the image horizontally by not using the anamorphic lens during playback.

Of course in the '50s and '60s they didn't have 27", 35" and 50" TV screens with top-notch resolution and color separation, so letterboxing was not an option. Neither was cropping, because a 2.35:1 image is almost twice as wide as a 1.33:1 and much important action would be lost if you just cropped the sides off a 2.35:1 image. So they either squeezed the image, which causes the actors and objects to look very thin, or they gave it a pan & scan (P&S) transfer -- or both, in some extreme cases (often title credits will be squeezed, while the movie will be P&S'd).

For P&S, a telecine operator watches the movie as it is being transferred, and follows the part of the frame (s)he thinks is important by panning, thus the term pan and scan. Some P&S transfers of widescreen movies are OK, others are horrible. Occasionally if two characters are on opposite sides of the frame, you either see one or the other, or both of their noses in a P&S transfer.

Of course problems with P&S are: it throws the image composition off, it still excludes important information in most scenes (such as entire characters that are important to the shot), and it produces motion artifacts if people are moving in the frame during a pan. And not least of all, it adds a whole style of "camera" movement on top of whatever the director had already done (or not done), sometimes significantly altering the feel of a film.

So in the 1980s when laserdisc started becoming a popular format, consumers started demanding films be shown in their original aspect ratio of 2.35:1, 1.85:1 or whatever. The Voyager/Criterion company was instrumental in starting the letterbox trend - introducing letterboxing with their release of Lawrence of Arabia, and letterboxing all subsequently released movies that had non-Academy aspect ratios. (Woody Allen also insisted on a letterboxed presentation of his film Manhattan on cable and VHS around the same time.)

A laserdisc letterbox movie should always look better than a VHS letterbox movie because it has more lines of resolution to devote to the image. But there is nothing about the medium itself that prevents VHS movies from being letterboxed (in Europe, letterboxed PAL releases are very common). But the average consumer who owns a VCR and a 19" TV usually wants the full screen filled. To many consumers the "black bars" at the top and bottom of the image, which are a natural result of letterboxing, detract from their movie-viewing pleasure.

To the movie lover and video enthusiast, it is a choice they will have to make for themselves. But to be objective, it is best to view movies of several different aspect ratios in both letterbox and pan-and-scan format.

4.2 How big must my TV set be in order to truly appreciate LD quality?

Actually, this is not a valid question. The size of your TV set has nothing to do with your watching enjoyment. However, the tv_size : viewing_distance ratio has everything to do with it. The bigger the ratio is, the bigger the image will look to you. If you watch a 5" screen from a distance of 5" with a cybernet helmet, it will look considerably bigger than a 40" TV set from a viewing distance of 6 ft!

Of course, in many cases the bigger and more expensive TV sets are of better quality, which will make the difference show up better. However, with a good 25" set and a 5-6 ft viewing distance (my current setup, with a ratio of approx. 0.38), the difference between LD and VHS is huge. And when I get the money and buy the Philips 32PW9781 16:9 receiver, which has a picture width equal to a normal 35" TV receiver, I get that ratio up to 0.52 with widescreen films (and to 0.40 on 4:3 material, but that's not so important to me).

You really only need a huge TV set or a projection system if you wish to show your movies for many of your friends at a time or you have another good reason to have a greater viewing distance.

4.3 Why do laserdiscs cost so much?

From Bob Niland's (rjn@csn.org) LD#01: ..but it can't even record?
Removed Fox from the expensive list April -97.

Discs cost about twice as much to manufacture as tapes, but new release discs often sell for less than new release tapes.

VHS tapes are the dominant home video medium. Most people rent tapes rather than buy them. The film studios don't get a percentage of the rental revenue, just the income from the initial sale of each prerecorded tape. Video stores are in hot competition to get new titles fast, so it is somewhat a "captive market." The first tape sales are therefore targetted at, and priced for, video rental stores - not for collectors.

Consequently, new tape releases are priced very high ($80-$90 is common). It is not until the the video store demand is satisfied that studios drop prices to levels attractive to individual movie collectors ($30-40). When that market is satisfied, prices may drop further for the mass market customers, $10-20 per tape.

In contrast, LD has been a "sell through" market. The major purchasers of new LD releases are individual movie collectors. LD rentals are not a big market, and there is no low-end mass-market at all. LDs, even major titles like Top Gun, are typically introduced at $30-40 (for CLV), and stay there. Many recent titles have come in at well below $30. Incidentally, routine 10% discounts are common for LD. I have a separate article, LD#14, available on LD mail order sources.

The exception to the generally low prices in the LD market is the Criterion Collection. Criterion releases run from $40-70 (CLV) and $60-125 (CAV). They are worth it because they seek out the finest possible source material (archival negatives, etc.) and deliver the most complete product, often with generous motion, still-frame and multi-channel audio supplements.

4.4 Sometimes I'll hear about a laserdisc about to be released and it's forever before it hits the stores. What gives?

Excerpted from Bob Niland's (rjn@csn.org) LD#01:

LD producers sometimes announce titles before they have the rights completely nailed down. This may be carelessness, but there are other causes as well, such as "surprise" old contracts that turn up late, and contain language that failed to anticipate LD (e.g. "We hereby assign to OneTimeVideo the LP, cassette and video tape rights to 'Revenge of the Valley Girls III'. All other rights are retained." So who has the LD rights?

LD producers also often announce titles after clear rights have been obtained, but before acceptable mastering source elements have been located. MGM/UA says the entire old United Artist vault materials are in sad shape. Criterion often announces it will offer a title when it gets the rights, long before they have collected, collated, annotated and transfered all the CAV supplements they are so famous for.

The practice of pre-announcing has the advantage that the major dealers often offer 15% pre-release pre-order discounts, sometimes as high as 25% on megatitles. The dealers get a larger discount on large initial stocking orders, and they can pass it on.

Once rights and source material have been obtained, the LD producer must schedule transfer time and pressing time, further complicated if closed- captioning or other special-processing is used. LD jacket artwork and editiorial content needs to be prepared as well. There are a limited number of video houses who perform quality, LD-compatible telecine transfers; fewer yet who offer digital transfers. There are only eight pressing plants worldwide that are routinely available for NTSC LDs. If they all are flooded with "megatitles", lower volume titles get delayed.

Pressing plant capacity also affects inventories of back-titles. New issues often sell-out, and are not re-pressed for six months or more. If you are just starting out in LD, expect some frustration in finding all the back titles you seek.

5. Defining the medium

5.1 What parties are involved in bringing a movie to laserdisc?

Excerpted from Bob Niland's (rjn@csn.org) LD#09: LD Mint Marks

There are at least six separate entities involved in getting visual works from the film/tape vault onto acrylic plastic and delivered to your hands:

5.1.1 The studio

e.g. "Universal", "Touchstone".

Ignoring Public Domain for the purposes of this discussion, the studio holds the copyright on the work in question, and usually custody of the archival film or tape elements. The studio may not actually initiate the LD release. Until recently, with a few exceptions (MGM in particular), the LD release was actually championed by the distributor. The studio merely grants permission and provides a key to the vault, so to speak.

5.1.2 The label

e.g. "MCA", "CBS/Fox".

The label hosts the release, lists it in their catalog, and may hold the home video rights as well. The label may also be a studio and is often a generalized entertainment conglomerate. There are well over 100 "labels" on LD in the U.S.

5.1.3 The masterer

(usually a manufacturer)

Converts the master videotape into a "glass master" for each side of the disc. Normally, glass masters never leave the manufacturer's control, but there have been reports of mixed mint marks, implying that one vendor made the masters, and another made the stampers and media. Glass masters are used to make one or more metal stampers that press or cast the actual disc media.

5.1.4 The manufacturer

e.g. "3M", "Pioneer".

The manufacturer presses (or casts, or injection molds) the media. They may also manufacture the disc labels, sleeves, jackets, and/or assemble the end product. With the exception of Pioneer, and some early 3M titles, manufacturers seldom act as "labels" or "distributors".

There are only six significant LD manufacturers in the continental U.S. There are at least five off-shore manufacturers that matter here, and perhaps more making discs in Japan for local consumption there. The significant sources are, in order of probability of encountering them:

• Pioneer Video Manufacring (PVM)
  aka Pioneer Video, Inc. (PVI) US
  aka Pioneer Communications of America (PCA)
• Pioneer Video Corp. (PVC) Japan
• DADC - Digital Audio Disc Corp. Sony-US
• DADC Austria Sony-Europe
• 3M US
• Mitsubishi Japan
• Technidisc US
• Philips-Dupont Optical (PDO) UK, "PDO"
• Kuraray Japan
• CBS/Sony Japan
• DiscoVision (DVA) US - long gone
• WEA Manufacturing (90% of Warner catalog from mid-91 to mid-93)

5.1.5 The distributor

e.g. "IMAGE", "LDCA".

The distributor warehouses the finished product, and ships it to retailers. A distributor usually publishes a catalog. A distributor may have exclusive access to certain titles, labels and studios. Some labels (e.g. Warner, MCA, Voyager and Lumivision) handle their own distribution (although non-exclusively). With the exception of Voyager Press, distributors generally don't sell directly to consumers under their own name.

There are only 2 broad-line LD distributors that really matter in the U.S.;

• Image Entertainment (IMAGE)
• Pioneer Laser Disc Corporation of America (LDCA).

5.1.6 The retailer

e.g. "LaserLand", "Sight & Sound", "Laser Disc Fan Club", "Columbia House".

The retailer sells directly to the public. Retailers may source from multiple distributors, so they theoretically can get you anything that is in print (or in a warehouse somewhere). The larger chains may handle their own distribution.

5.2 So laserdiscs are just like big CDs with movies on them, right?

Excerpted from Bob Niland's (rjn@csn.org) LD#01:

There are three major types of consumer laser video media:

• 12-inch video discs,
• 8-inch video discs, and
• 5-inch "CD-Video" discs (CDV5).

The traditional 12- and 8-inch media are of acrylic construction, and are always two-sided, although sometimes only one side contains program material. LDs are literally two single-sided discs glued together, and the edge of the disc is often sticky for this reason.

There are some 8-inch LDs that are made exactly the way CD's are - complete with the painted labeled on the non-playing side. LDs that will play CDs have no problems with these. Older players need a 'shim' disk, which is placed over the real disk in the player. This give enough thickness of the clamping mechanism to work. Otherwise these are not playable in older machines. The advantage of these are that they can be produced exactly as a CD can. However, these discs are rare.

The 5-inch (CDV5 or just CDV) is single-sided, and can contain about six minutes of full-motion video/audio plus 20 minutes of audio-only. As with CD, CDV5 is polycarbonate on the data side, and lacquer on the label side. Any LD player that can handle CDV5 can also handle audio-only CD. CDV is all but defunct in the United States but still popular in Japan.

At present, no LD combi players can handle the new CD-I full motion video and VideoCD formats. Since the basic quality and nasty artifacts of these highly compressed formats render them less pleasant to watch than VHS, they aren't likely to be of interest to anyone seeking laser quality home theatre.

CD-I and VideoCD don't appear to be much of a threat to LD. Anyone interested in LD is apt to be in the market because they are weary of the limitations of VHS. One look at 5-inch compressed digital video will make it clear that CD-I and VideoCD are no alternative to LD, and aren't even a net improvement over VHS for home theatre purposes.

Other buzzwords: LD players (whether combi or not) do NOT presently support CD-ROM, or CD-ROM/XA (audiofiles), DVI, CD-I (interactive multi-media) and VideoCD formats. Until recently, only Karaoke LD players supported CD+G subcode text. Pioneer has "LaserActive" players which support CD+G, LD-G, Sega CD-ROM games, Genesis 16-bit game cartridges, and a new format: "MegaLD" 8- and 12-inch LD-ROM2 discs.

5.3 What's all this talk about NTSC, PAL and SECAM?

Currently there are three dominant video standards is the world, namely NTSC, PAL and SECAM. As LDs are only made for NTSC and PAL systems, this article will not cover SECAM. You can get more detailed information about the different TV systems from BBC Aberdeen, http://www.bbc.co.uk/aberdeen/tech.htm.

5.3.1 NTSC

NTSC stands for National Television Systems Committee, and is the TV system used in North-America and Japan. It has 60 fields (30 frames) / second, 525 horizontal scanlines (480 visible), and a 3.58 MHz colour carrier wave. Only LDs made for the North American and Japanese market are NTSC.

As with VCRs, the only significant "grey market" media sources for North American customers are Japan and Hong Kong. Encoding is really a non-issue for NTSC consumers, and U.S.domestic discs are sometimes not even labelled "NTSC".

There is a problem with movement when transferring a film to NTSC: 30 frames/s, or 60 fiels/s of NTSC is not divisable with the 24 frames/s used in almost all films. The problem is solved in the following fashion: Two consecutive film frames lasting 1/12 s are taken. The first film frame is shown for 2 NTSC fields (2/60 s). The second film frame is shown for 3 NTSC fields (3/60 s). This makes a total of 5/60 s for NTSC video, which also makes the 1/12 s the original film frames were supposed to last. This system is called 3/2 pull-down.

There are drawbacks in this pull-down system: to some viewers (me included), slow panning looks much more jerky in NTSC compared to the original film experience, or PAL, which typically uses 2/2 pull-down.

5.3.2 PAL

PAL stands for Phase Alternating Line, and is the TV system used in the civilized parts of Europe, and China. It has 50 fields (25 frames) / second, 625 horizontal scanlines (585 visible), and a 4.43 MHz colour carrier wave. PAL discs will not play on current American machines. The PAL LD (also called LV or CDV) catalog is about 1000 titles at present. However, multi-standard players are available in Europe. These may or may not require a multi-standard TV/monitor.

Because films have 24 frames/s and PAL has 25 frames/s, it is most convenient to show movies at the frame rate of PAL. This makes movies last 4% less time and makes all voices little higher. Usually this makes little difference, but for me watching Pink Floyd's The Wall in PAL is almost like torture.

5.4 What is "CX noise reduction"?

From Bob Niland's (rjn@csn.org) LD#01: ..but it can't even record?

CX noise reduction is the rough LD equivalent of Dolby-B for audio tapes. CX is only used on the LD analog channels. There has been a lot of debate about CX. Criterion, for example, only uses CX when the original audio source material has wide dynamic range (i.e. frequently not on early optical soundtracks mastered on film). They do not use it where the programs on the two channels are different, as it can cause decoder mistracking.

5.5 What does CLV and CAV mean?

Excerpted from Bob Niland's (rjn@csn.org) LD#01:

Rotation modes: LDs can be mastered for either constant linear velocity (CLV, variable rpm), like a CD, or constant angular velocity (CAV, constant rpm), like an LP. All consumer players can handle either format. Some releases even mix the modes, with the initial sides being CLV and the final side being CAV. Some films are initially released in both CLV and CAV "collectors" editions.

CAV is also known as "standard play" or "full feature play". Only CAV provides all motion control capabilities on all players (at the expense of more platters and shorter 30 minute sides). CAV also provides constantly improving signal-to-noise ratio as the program proceeds toward the outer edge, but this is typically not that noticeable on properly manufactured discs.

CLV is also known as "extended play". One hour per side playing time results in lower prices and less flipping. In return, you give up all the other CAV features, unless you have a high-end player with digital field store.

The majority of disc titles are available only in CLV.

A Comparison Between CLV and CAV discs on different players (NTSC discs):

 
 
Ordinary

Player

Digital

Player*


Disc format

Rotation velocity (rpm)

Maximum time per side (minutes)

Simple fast forward/reverse

Variable fast forward/reverse

Variable slow forward/reverse

Pause (with blank display)

Still frame (field on digital CLV)

Still step

Seek to chapter

Seek to time

Seek to frame number
CAV


1800

30

Yes

Yes

Yes

Yes

Yes

Frame

Yes

No**

Yes
CLV


1800..600

60

Yes

No

No

Yes

No

No

Yes

Yes

No
CLV


1800..600

Yes

Yes

Yes

Yes

Yes

Yes

Yes***

Yes

Yes

No

5.6 What is CAA then?

CAA stands for Constant Angular Acceleration.

To be exact, the discs that nowadays are entitled CLV, are actually CAA discs. In CAA the disc speed is not slowed down constantly, but it is kept constant for some time and then rapidly slowed down. The point in this system is to keep the horizontal sync signals aligned on adjacent disc tracks to keep crosstalk to a minimum. In Blaine Youngs (Blam1@aol.com) words:

"CLV: This format is dead. The name is still used for simplicity's sake, but 3M is the only manufacturer which uses it. In 1982/3, there was a shift to CAA. This is the only format used today. (Again, except for 3M which incorporates a minor variant on CLV to eliminate crosstalk). Regardless of which format is used (CLV or CAA) it is still required to have crosstalk rejection code built into the mastering software to prevent master crosstalk. Technidisc does not use such software and as a result, most of their CLV stuff looks like crap.

CAA also offers something else, 5 different encoding routines. This will allow for variable playback times, depending on the program. What happens is that the initial CAV pattern at the beginning of the disc is altered (lengthened or shortened as necessary) and the track pitch is modified. The 5 formats are CAA45, CAA55, CAA60, CAA65 and CAA70. CAA45 has been used only once, that I know of. Any disc side running less than 55:05 uses CAA55 encoding. All other discs are CAA60. There are 2 known occurances of CAA65 and there has never been a CAA70 disc released in the US."

From now on, CLV and CAA discs are just called CLV for simplicity, and because that's what's written on the disc sleeves.

5.7 What is the qualitative difference between CAV and CLV?

From Michael Gebert (MGMax1919@aol.com)

While technical differences between CAV and CLV are discussed below, it should be noted that the choice of format is only one factor, and not necessarily the most important one by any means, in determining the eventual quality of a disc. The care taken during the mastering process and the condition of the source materials are of at least as much importance. With the improvements in mastering capabilities over the years, it is not unknown for a CLV disc released today to look and sound better than a CAV disc mastered several years ago (e.g., the new Criterion transfer of Citizen Kane compared with the one that was released in the mid-80's as the very first Criterion Collection disc). In short, the technical differences between CAV and CLV are discernable only at the ultimate point of the respective formats' capabilities. The best CAV disc will look and sound better than the best CLV disc, but a good CLV disc will look much better than an average CAV disc-- while even the best VHS tape won't compare with any competently made disc.

Leopold continues with a table comparing CAV to CLV:

• + Better colour S/N ratio. There is some minor amount of colour noise evident in CLV discs and in the beginning 4 minutes of CAV discs. After this, however, the linear speed of the disc goes high enough to disable any visible noise (that wasn't in the original masters).
  
  
• + All special video effects available on all players. You can have a full resolution still-frame on all players, and you can scan through the disc with as perfect a picture as your TV system allows.
  
  
• + The pictures can be handled as separate images. This feature is often used in special editions of movies to let the user see production fotos, manuscripts etc.
  
  
• + The LD player can automatically pause when a CAV disc switches from live motion video to still frames.
  
  
• + Faster access times.
  
  
• + Cross-talk is generally invisible on CAV. Crosstalk usually appears as herringbone patterns on the screen, and can result from an LD mastering defect (A), player misadjustment (B), or even master tape problems. In cases A & B, CAV can make the problem invisible, because on CAV the adjacent lines are:
  • aligned in time
  • often identical to the current line
  • at least contextually related to the current line, so the visible effects of crosstalk are minimal or invisible

  In CLV the adjacent lines are:

  • misaligned in time even if identical in content at start-of-side;
  • from distant parts of the frame image (contextually unrelated) as the side progresses;
  • usually contain horizontal retrace interval junk (including large video pulses) during the active line period of the desired scan line, so any crosstalk is likely to be quite visible.

  The problems mentioned here have been mostly fixed with a technology called CAA, where the disc speed is changed in steps so that the horizontal retraces always overlap. The discs are CLV compatible, but the risk of getting herringbone patterns are much smaller.
  
  

• Point defects on CAV tend to be stationary; they scroll on CLV. On CAV, they affect the same pixel, scan line or group of lines in a sequence of frames. CLV defects tend to scroll (faster toward side end). Which of these is more obnoxious is a matter of opinion.
  
  
• - More disc flipping on live action video (max 30 minutes on CAV vs. 60 minutes on CLV (36 and 64 for PAL)).
  
  
• - More expensive due to the higher amout of discs.
  
  
• - More noisy, because the disc speed doesn't decrease towards the end of the disc.
  
  

But does a CAV disk produce a better picture than a CLV disk?

For free-run playback, not really. There is a quality difference between CAV and CLV, but it is small, and way less dramatic than say, S-VHS vs VHS.

Of course, for seek/still/step/slow/fast, CAV is at least twice the image quality of CLV, and on most players, offers functions that CLV discs can't duplicate.

5.8 What is the difference between Dolby Surround, Pro-Logic, Dolby Digital, AC-3, DTS and THX?

Excerpted from Bob Niland's (rjn@csn.org) LD#03: The soundtrack comes after you..., and revised by Leopold (mods to THX, added Dolby Digital and DPL synonyms)

A branded "Dolby Surround" decoder:

• sends Lt-Rt (surround) thru a delay line (typically 20 mSec),
• then thru a 7 KHz low-pass filter (to keep natural and azimuth error caused left/right source phase noise from being heard as surround) and
• thru a 5 db (vs 10 on audio cassette) Dolby B-type noise reduction circuit.
• Lt and Rt are isolated, and may also be summed (Lt+Rt) and sent to the Center output.

  In any case, a maximum of 3 dB of separation is achieved between each adjacent pair of: left-center-right-surround-left.

A Dolby Pro Logic decoder starts with Dolby Surround, and

• replaces the simple Lt-Rt (surround) and Lt+Rt (center) extractions with an active adaptive matrix decode step. For signals intended for one output, this circuit attempts to cancel them in the others.
• It also analyses the soundfield for signal dominance, and focuses the sound toward those outputs. The net result is that 30 dB of separation is possible between any two channels.
• Input balance is required.
• Lexicon Pro-Logic decoders also include an "auto-azimuth" feature to correct for group delay errors (time shifts) between the two source channels. Shifts as high as 50 microseconds are reportedly common in film-sourced sound (45 degree phase shift at 5 KHz).
• Encoding schemes that are 100% Dolby Pro-Logic decoder compatible are Dolby Surround, Dolby Stereo, Ultra*Stereo, StereoSurround, Matrix Surround, MP Matrix, DTS Stereo, Chase Surround, Surround Sound, Circle Sound, Circle Sound 360, Shure Stereo Surround, DynaQuad, EV-4.

When a Dolby Digital (DD) -encoded laserdisc (which used to be called Dolby AC-3) is played on a Dolby Digital player and the audio is fed to a DD decoder

• the listener is offered five discrete channels of highly compressed full frequency range sound (5-20000 Hz), plus a special subwoofer channel (2-120 Hz).
• The channels are totally discrete. There is no crossover whatsoever between the channels, and channel separation is perfect.
• The DD sountrack occupies the space that has earlier been used for the right analog audio channel. The digital channels are left intact.

When a DTS disc is played with a laserdisc player that has a digital audio output and the output is connected to a DTS decoder

• the listener is offered five discrete channels of moderately compressed full frequency range sound (5-20000 Hz), plus a special subwoofer channel (2-120 Hz), just like with Dolby Digital.
• Just like Dolby Digital, the channels are totally discrete.
• The DTS soundtrack occupies the space normally used for digital sound. Thus people without DTS decoders can only listen to the analog audio track. This makes the system less downwards compatible than Dolby Digital.
• DTS laserdiscs are strictly speaking not laserdiscs at all. They are not a part of the official standard. At this moment (April -97), only a handful of titles are available (less than 10, I think).

LucasFilm THX

THX is not another encoding scheme. It's just a quality assurance system that tries to take the most of Dolby Pro-Logic. (Don't confuse this with THX certified discs, we are talking about audio decoding hardware now.) A THX-certified processor starts with Dolby Pro-Logic and adds

• Surround channel decorrelation - a digital pitch shift is used to make the (mono) surround signal "different" in the left and right surround channels.
• Re-equalization of the front channels, to make the movie mix seem less "bright" in the home.
• "Timbre Matching" - an equalization applied to the surround channel to make effects sound consistent when panned between front and surround speakers.
• THX has also become a LaserDisc certification program. The first title with "THX quality" presentation parameters was the director's cut of "The Abyss", released in 1993. Nowadays most major releases has the THX certificate.

THX specifies front speakers with a reduced vertical dispersion (to minimize ceiling reflections) and two side-mounted surround speakers configured for dipole radiation. THX is also a certification process for video programming, beginning with LaserDiscs in early 1993. As with Pro Logic, THX-branded audio material is not "THX encoded". THX mixes are merely a specific way of performing Dolby-MP sound mastering. A THX-certified LD presumably will have purist aspect ratio, source element/transfer quality, colorimetry/timing, etc. The telecine monitor is calibrated by LucasFilm and a "THX Vertical Interval Test Signal(TM)" is inserted during NTSC encoding of the signal.

5.9 What is an anamorphic, or 16:9 transfer?

In a 16:9 disc (also called anamorphic disc) the picture is stretched vertically 33% (4/3*100-100), and when played back with a normal TV set you see this stretched image. When played with a 16:9 TV set or with a TV set with a 16:9 switch, the original aspect ratio is restored. Here in Europe at least all of the mid- and high-end Philips and Sony 4:3 TV sets offer this button, and this mode is available on all 16:9 TV sets that I know of.

The advantage is this: in a normal 2.35:1 NTSC transfer you get approx. 273 active video lines (482*1.33/2.35), but with a 16:9 release, you get approx. 364 lines (273/(4/3)*(16/9)). This will reduce line flicker and greatly enhance vertical resolution compared to a non-anamorphic representation.

The same numbers for a 1.85:1 film are 347 and 475 lines. And this is really interesting: with this film format the 16:9 version has to leave only 7 NTSC video lines unused. Thus, you get the full resolution of NTSC in a widescreen release!

Naturally, to make an anamorphic version of any picture material that is less wide than 16:9 (1.78:1) would be counterproductive, because then you would have to leave black bars on the left and right side of the screen and begin to lose horizontal resolution that way.

So far only few titles have been released in 16:9. As I'm writing this (96-07-24), some titles have been published but none are available at the moment in USA. However, several titles have been announced for publication in Japan, including T2, Basic Instinct, Cliffhanger and Stargate (all in Dolby Digital).

6. Rivals of laserdisc

Laserdiscs are of course not the only movie media on the market. In this chapter I'll make a little comparison between LDs and some other popular video formats. For a technical comparison, look at my www-page Home Video Formats, http://www.cs.tut.fi/~leopold/Ld/VideoFormats.html.

6.1 VHS

VHS is naturally the biggest rival of LDs, and in the late 80s it almost killed the format. Not because of the quality, but because of clever marketing (can you spell C-cassette, PCs and Windows-95?).

Qualitywise VHS is worse in every aspect: Less luminance resolution, less colour resolution, more picture noise, no digital sound, tracking problems, plus normal tape wear and tear. But, Joe/Jane Average doesn't care of the picture is bad. He/she doesn't even care if 40% of the original area of the picture is lost in a panned and scanned (P&S) version of his/her favourite movie.

S-VHS is much better, but there is no program material available for it. Enough said.

6.2 CD-I and VideoCD: The digital 5" CD-ROM -like laserdiscs

Philips claims CD-I to have a clean and sharp digital picture. Sure. The truth just happens to be that when a film is tried to cram in the same bandwidth that CDs use just for sound, the result is no good. Although the theoretical resolution of CD-I is somewhere around 320x256 pixels (240x256 lines), a transition from black to white can't happen in one pixel. This makes the real resolution look more like 200x180 pixels. This is even worse than VHS, which has a resolution of somewhere near 320x585 pixels (240x585 video lines) for PAL, or 320x482 pixels for NTSC.

When the images are not moving, CD-I appears to have a steady and non-noisy look. But when the picture has much movement, the very low picture data rate of 1.1 Mbits/s makes the picture break into little 8x8 and 16x16 pixel MPEG-1 -compression blocks, which makes any action film look totally disgusting. When you are supposed to be lost in high action, you are lost in compression blocks.

CD-I discs are claimed to be both NTSC and PAL compatible. This is carried out with an evil scheme: the discs are mastered in a way that makes everything appear 10% too flat on PAL TVs and 10% too tall on NTSC TVs. I find this way of solving problems to be totally unacceptable.

The video compression ratio on CD-I is approx. 40:1 and audio compression ratio is approx. 5:1.

6.3 DVD: The new digital 5" laserdisc

DVD is a new 5" digital video disc format, that has digitally stored information much like CDs. It uses MPEG-2 compression, and because of a high data rate it is supposed to give you approximately LD quality picture and good multi-channel audio. At this moment (April -97) first DVD players and discs have been published in USA, and first reports of the picture quality are quite favourable.

Most of the first 30 or so US titles seem to have an anamorphic letterboxed version of the film on the other side of the disc and a full-screen 4:3 version (either open matted or pan & scan) on the other side. This is of course good news for the videophiles.

At least high-end DVD players have some kind of component-based picture opposed to the composite picture in LDs, and with a component onnection similar to RGB the colours might look a better than LD. Also many players have Y/C connectors, which already is a good step up from composite video.

A typical picture compression ratio for DVD is 60:1 (for a 3.5 Mb/s video stream portion) and 10:1 for audio. However, the picture compression ratio can vary greatly because of the dynamic bit allocation rate and a requirement to be able to sustain a 9 Mb/s data rate if needed.

The DVD Frequently Asked Questions can be found at http://www.videodiscovery.com/vdyweb/dvd/dvdfaq.html. It is also available locally herre at the Laser Rot site at http://www.laserrot.com/infobase/techcorner/dvdfaq/dvdfaq.html.

Addendum 97-04-09:

Yesterday I had the first chance to test DVD at my home. I used the following equipment:

• Pioneer CLD-1850 LD player using composite connection.
• Toshiba ST3006 DVD player using S-video connection.
• Philips 32PW9631 32" 16:9 IDTV set (which has extremely good comb filters), with a watching distance of about 1 meter (3ft 4").
• Widescreen versions of The Fugitive and Blade Runner DC both on LD and DVD.

I did a head-to-head comparison with the titles mentioned. I used 16:9 anamorphic mode to watch the DVD titles. And what did I see?

The Fugitive:
When viewing DVD frame-by-frame, the noise in the original master generated slight compression artifacts almost all the time. Most of the time the artifacts could be seen even when playing if you watched really carefully. In some frames the artifacts looked really bad, the worst cases being @ 1:07:41-42 and 1:21:01. However, when running side by side, using the LD's CAV side for comparison, and using anamorphic picture for DVD, there was a definitive difference in picture quality: DVD was much sharper in both horizontal and vertical directions, it lacked all problems with cross luma and chroma in the very thin blue opening titles as well as everywhere else. DVD also had more texture especially in people's faces because the signal didn't have to be comb filtered, and it had practically no chroma noise. To be honest, I was shocked how much better all these slight, incremental changes made DVD look.

Blade Runner:
Here the difference was even bigger: there is no noise in the master and the compression works much better. There are practically no compression artifacts. The picture is sharp, noiseless and clean. When I switch to laserdisc, I get an ugly VHS feeling. Honest!

When I switched the player to 4:3-downconvert (for normal TV sets), DVD picture quality was degraded quite a bit. It was still slightly better than laserdisc. When, in addition to this, I switched to composite video, the difference of DVD and LD all but vanished.

That's it. DVD is definitely better than laserdisc in picture quality. Even my girlfriend could immediately tell the difference, and she is no techno freak like me. Now we just have all this hassle with the stupid DVD country codes, incompatible video systems and macrovision.

Created: 04/16/97
Last Updated: 04/17/97