Talk:LaserDisc

Analog or Digital

I've heard more than once that the LD is actually completely analogue (at least for the video part, if not the audio), rather than digital like the CD. Can anyone knowledgable confirm and add info about this? --radiojon 07:29, 3 Sep 2003 (UTC)

That's my knowledge as well - a quick google found the following short technical description [1]. andy 07:39, 3 Sep 2003 (UTC)

I have read more than once that audio could be analogue or digital, but video was always the same(i forget which). What I never understood is: how on earth do you store analogue signal by anything other than depth(as in a record read by a needle)?Boffy b 00:12, 2004 Sep 26 (UTC)

I think this is how it works. The video signal is used to frequency modulate a carrier signal, and the resulting signal is clipped and stored on the disc as a square-wave-like signal. Each transition from pit-to-land or land-to-pit represents a transition of this FM video signal from positive to negative, or vice versa. When the signal is read off of the disc, the harmonics are filtered out, turning the square wave back into a modulated sine wave, which is then demodulated and turned back into video. Someone correct me if I'm wrong. --Arteitle 06:10, Sep 26, 2004 (UTC)

Yes, from what I remember reading about LD a while back in a book about TV & video systems, this sounds right. The space between the pits on a LD represents the FM-modulated space between the "peaks" and "valleys" of the waveform representing the whole carrier (video, audio, and all). Basically, it's a form of analog Pulse-width modulation,or PWM. -- misternuvistor 03:24, 11 October 2005 (UTC)

LD FAQ link

> I've heard more than once that the LD is actually completely analogue

http://www.access-one.com/rjn/laser/legacy/ld96.html

The article author might want to link to the hosting page for the above, as there are numerous FAQs, some more recent than those linked from the wik article.

http://www.access-one.com/rjn/laser/laserdisc.html

Resolution is measure of VERTICAL Lines

When you talk about a video resolution in terms on LINES, this refers to an old analogue mesaurement system where you determine the number of vertical high-contrast lines you can resolve. "400 lines" refers to 400 vertical lines could be distinguished (this would correspond to about 800 pixels across) compared to the 250 lines (about 500 pixels) of VHS under ideal conditions. For this reason, I changed the section that talked about resolution from saying "HORIZONTAL" lines to "VERTICAL" lines. Don't confuse resolution with the number of "SCANLINES" a format uses. Swirsky

As far as i know, the resolution "400 lines" for laserdisc means 400 pixels horizontally - 200 line pairs (to use the correct term of the analogue world), while VHS hast about 250 lines/125 line pairs. In the following section of the text someone got it wrong:

"The image resolution is also greater for DVDs for two reasons. Firstly, NTSC laserdiscs offer 400 lines of resolution while DVDs offer 480 lines. PAL laserdiscs offer 440 lines of resolution while DVDs offer 576."

480 lines NTSC and 576 lines PAL mean VERTICAL lines and have nothing to do with the horizontal resolution - even the worst VHS offers 480 lines (NTSC) and 576 lines (PAL) in the vertical dimension. Theoretically, DVDs offer a full resolution of 720 lines (horizontal), but a comparison to the 400 lines of the Laserdisc makes not sense at all, because of digital compression (DVD) and limitation of sharpness/Aperture correcture due to noise (Laserdisc). (MalteRuhnke, German Wikipedia)

Jesus H. Christ on a pogo stick, you are both so utterly wrong. In the video world, HORIZONTAL resolution is known as COLUMNS, while VERTICAL resolution is known as LINES or ROWS. This means that the computer resolution of XGA is exactly 1024 columns wide by exactly 768 lines tall. ALL raster video images are made up of PIXELS, including NTSC/PAL/SECAM/VGA/whatever, which means that a pixel is a pixel no matter the system.

This definition still stands whether or not the image is progressive, interlaced, overscanned, analog, "digital", RGB or YPbPr.

All home video and television systems always have the exact same horizontal resolution (columns) as the TV system (I.E.: either NTSC or PAL/SECAM) they're using, their visual granularity differed ONLY in terms of vertical resolution (lines or rows).

I'll dig up the actual resolutions of the different formats sometime and update the article. 207.177.231.9 16:44, 20 July 2007 (UTC)

You're the one who's wrong. Horizontal resolution is often expressed in lines or line pairs, in which case they mean vertical lines of course. Furthermore, analog video is not composed of pixels. Pixels are discrete units, analog video varies infinitely (the actual information is constrained by bandwidth and noise). MalteRuhnke is correct, however he uses the incorrect term "Vertical lines" when referring to vertical resolution, when the vertical resolution would be defined by _horizontal_ lines. 400 vertical lines (a measure of horizontal resolution) corresponds to 400 pixels. Your last paragraph is also wrong. _Vertical resolution_ often doesn't change (480 or 576 visible lines depending on which broadcast system was used). Horizontal resolution can vary depending on the bandwidth. TV broadcasts have more bandwidth than VHS for example, so VHS has worse horizontal resolution. Totsugeki 00:59, 16 August 2007 (UTC)

(1) Please don't use curse words. It's rude. (2) Horizontal resolution is measured by drawing a perfect circle on the screen, and filling that circle with vertical lines. (3) You then count left-to-right to see how many lines can fit inside that circle without blurring into a grey smudge. (4) The result is expressed as "420 lines horizontal per picture height". (5) If you want to convert that value to digital terminology, just multiply by 4/3, which yields approximately (key word) 560 pixels edge-to-edge, horizontally.

The vertical resolution is fixed by the number of scanlines. i.e. 486 for NTSC, 576 for PAL, 720 for ATSC-progressive, or 1080 for ATSC-interlace. - 15:37, 11 October 2007 (UTC)

I reviewed my comment and can't find any curse words. I agree with the rest of your comment, except that ATSC-progressive can also be 1080 lines (see the ATSC article). I did say the exact same thing: vertical resolution depends on the TV system. The comment I responded to contained this completely incorrect statement: "All home video and television systems always have the exact same horizontal resolution (columns) as the TV system (I.E.: either NTSC or PAL/SECAM) they're using, their visual granularity differed ONLY in terms of vertical resolution (lines or rows).". Totsugeki 16:31, 11 October 2007 (UTC)

All of the above is true

The Total Rewind VCR museum has the whole story, but in short it was released in 1980 as DiscoVision/LaserVision/VLP(30cm, all analogue, flopped), in 1988 as CD-V(20cm, digital CD sound, analogue video, flopped), and in 1991 as LaserDisc(same as CD-V, but 30 cm and sometimes with analogue audio as well, fairly successful).

Read all about it at [2]

More

Laserdisc is an entirely analog format where the video portion is concerned. Some people find Laserdisc slightly more attractive than DVD because it does not suffer from compression related issues and has a smoother more "film like" image. However, it was also prone to issues such as "crosstalk" which DVDs do not suffer from and DVD has 30% greater overall resolution. In addtion, Laserdiscs had the capability to store digital audio, a capability that was regularly made use of in the early and mid 1990s, up to 1997 or so when the format finally died. Dolby Digital and DTS debuted on the Laserdisc format. I have several websites earmarked which contain information on the development of Laserdisc, catalogs of titles that were released and even lists of which titles contained Dolby Digital and/or DTS sound. If you are interested, or have a general question, I can be reached via e-mail at OneActor1@aol.com

"Some people [videophiles] find Laserdis slightly more atractive than DVD..." These people are the video counterpart to audiophiles thay favour vinyl over CD, arn't they.

In the line "NTSC discs could carry two analog audio tracks, plus two uncompressed PCM digital audio tracks, which were generally CD quality or better." I was wondering why you added "or better" after the description of "CD quality". As I mentioned in my earlier edit comment, the specs for Laserdisc's PCM tracks are the same as CD: 44.1 kHz, 16 bit, stereo. --Arteitle 19:34, Nov 13, 2004 (UTC)

CDs aren't compressed (PCM). Also high quality tapes are arguably better analog quality then vinyl. Nil Einne (talk) 11:28, 23 February 2008 (UTC)

It was my understanding that the nature of LD-Audio storage allows for higher than CD audio quality. This is laregly the result of the audio being uncompressed, where it is compressed on CD. Basic listening tests have led me to believe that this is both possible, and in some cases true. Although I suppose that this could be the result of mastering differences.

Your post is largely true and informative, except for the bit about CDs. Standard music CDs are uncompressed, but both the video and audio on DVDs is compressed which may be what you are referring to. Boffy b 20:51, 2004 Nov 15 (UTC)

That doesn't make any sense. The audio on CDs isn't compressed. Nil Einne (talk) 11:28, 23 February 2008 (UTC)

Comb Filtering

Comb filters are a way of keeping chroma subcarriers from interfering with luminance signals (as a beat pattern) *when you mix them*. Clearly, if you're taking the video off the S-Video connector, that's not an issue.

If you can find a citation that the comb filter was explicitly intended to make the S-Vid out look better (as opposed to the composite out) which is *not* marketing material (:-), please post it, and I'll retract. Baylink 07:14, 4 Dec 2004 (UTC)

The reason a comb filter is always in the signal chain with LD is because the video is stored on disc as a composite signal. So using the S-Video output of a LD player means separating luma and chroma in the LD player (and using its comb filter), whereas using the composite output of the LD player means separating them in the TV (and using its filter). See [3] (part of the LD FAQ). --Arteitle 13:32, Dec 4, 2004 (UTC)

Well, I will be dipped in shit. I had managed to completely miss that it's composite on disc. Nice reference, BTW; is that in the main article? Baylink 22:19, 4 Dec 2004 (UTC)

Yow, don't take it so hard. :) Yeah, it's in the external links. --Arteitle 23:12, Dec 4, 2004 (UTC)

DVL-919

The DVL-919 is still on Pioneer North America's website but is NOT in production any longer. It's been out of production for the U.S. since around 2000. I verified with several Pioneer dealers, I also verififed that a few units are "floating about" but that Pioneer no longer consideres it a current model. The Laserdisc section of the 919 was borrowed from an older player in the CLD-600 series, which were never very good players and the DVD section is mediocre at best in comparison to most new units from Pioneer, Toshiba, etc... and Pioneer made the decision to drop it when support for LD fell through completely in the U.S.

Fine. But please *correctly* characterize your changes, don't take the website reference out of the article completely... and sign your damn changes.  :-) Baylink 22:15, 5 Dec 2004 (UTC)

I don't understand how I'm failing to properly characterize my changes. The reference to the DVL-919 being on the website is moot and doesn't need to be in the article. On the site or not, the manufacturer consideres the player dead and says they've ceased all production, as of 4 years ago. In any case, I'd sign my changes if I knew how, but I don't. I'm not entirely sure why it matters, it's not as if I'm filling the article with derogatory comments or bad information. You guys that desperate to track me down?

No, it's simply what one does. Since you're not signed in, you haven't anything to sign as, anyway. But don't be surprised if your lack of desire to set up an account and take responsibility for your changes makes them slightly less important to others.

There is no clear public evidence that the manuracturer considers the item dead: this is an encyclopedia; we don't do primary research. "Private communication" is not an acceptable source. As slow selling an item as it is, ceasing production 4 years ago doesn't at all have to mean that they don't have them available in their channel. Baylink 19:10, 10 Dec 2004 (UTC)

I won't debate this with you any more. I'll only add that any member of the public need only contact a local retailer or consult Pioneer directly to find that the 919 is a non-production unit and is no longer supported by the manufacturer. It's an obvious case of a company failing to update a portion of their website. Slow sales has nothing to do with the situation, this is not an issue of a manufacturer cutting back production numbers in response to waning demand, it is an issue of ceased production. The 919 is no more current than a 1995 Corvette, on the website or not.

All of which is immaterial to the fact that the information in question is primary research, and thus not fit for Wikipedia. And "is no longer supported" is not a subset of "no longer for sale", either. Clarity, please... :-)

My DVL-919 has a manufacture date of December 2003. So it certainly was NOT discontinued in 2000.

Disruptive technology?

When they were first introduced, laser discs were believed to be disruptive technology, a promise they failed to fulfill.

The term "disruptive technology" was not coined until 1997. Can you call LD the "disruptive technology"? -- Toytoy 08:44, Feb 6, 2005 (UTC)

The term didn't exist in the 1980s, true, but the concept was there in the marketing. There was a clear belief on the manufacturers' part that it would supplant videotape due to superior picture quality.

Perhaps it should be amended to "what would later be described as ..." — Daniel Case 05:20, 4 Jun 2005 (UTC)

In order for a new technology to be disruptive, there needs to be an already-existing standard that dominates a market. For example Compact Cassettes: In the late 70s, the newbie known as cassette overthrew the dominant tech known as the phonograph, and the Cassette became the preferred choice of consumers, thus the cassette was "disruptive". Getting back to laserdiscs: In 1978, there was NO dominant video technology. - Theaveng 15:43, 11 October 2007 (UTC)

Laserdisc Introduction

By the time the format was brought to market in 1978, the hyphen was removed from the format name. They marketed it under the name DiscoVision beginning December 15, 1978 after the earlier CRV disc format had died out in obscurity.

Could more knowledgable members please rewrite, delete, or elaborate on what "the earlier CRV disc format" was that died out? Just to be sure, what does "CRV" stand for?

There's some minimal expansion on what CRV was in the variations section of the page, which I've already sort of been thinking of moving because it isn't really a variation of Laserdisc, it's an earlier format. IMO, anymore info on CRV than what's already here should be on a CRV specific page, as the minimal reference to and explanation of the format that are on the LD page are all that are really neccesary in context to the Laserdisc format, which was a seperate entity.--Flash-Gordon 11:01, 23 May 2005 (UTC)

That scroll button is going to be the death of me... but I digress. I found the passage in conflict to that I know about history of video discs: I initially thought that the "earlier CRV disc" as a reference to RCA's CED format (or some other obscure/still-born format of the time). When "CRV" is defined later in the article, it seems a anachronism that recordable video discs where available around the time of Laserdisc's introduction. If I am wrong, could some please enlighten me? --Kevin586 22:03, May 23, 2005 (UTC)

a long time reader first time writer adds: the CRV comment early in the article is confusing, especially since it's not explained until the (very) end. I agree with kevin that it's mostly irrelevant. Another unrelated thought: perhaps it's worth mentioning (or linking to) the Dune laserdisc where the rare/high demand discs are mentioned; the "six hour version" (which is really only about four hours) is only available on japanese LD, and not all the SFX are "finished".

-- cz May 25, 2005

Kevin - CRV discs were recordable (with the proper equipment) caddy-discs (see the picture in the article) originally intended for use as A/V carriers like Discovision/Laserdisc. The format proved a failure for multiple reasons and AFAIK, was unrelated to CED, although it did find limited use as a backup medium before tape drives, ZIp and JAZ drives and recordable CD media was avaliable. I added the comment about the "earlier CRV format" because, as it was explained to me, the movement from MCA into Discovision was largly driven by the failure of the CRV format. I know fairly little about the CED and CRV formats in practice, but if the consensus is that the CRV reference should be removed, modified or moved to a seperate page (which is where I'm leaning) than that's what should be done. --Flash-Gordon 09:00, 31 May 2005 (UTC)

Yes, Flash-Gordon is right, but CRV, AFAIK, was not the name for the prototype MCA/Universal/Discovision LD system released in 1972, nor was it another name for RCA's CED system (which was either known as CED, or SelectaVision). CRV was a recordable system developed by Sony in the late 80's-early 90s and it's official name is "CRVdisc". Plus, I don't think there were any pre-recorded CRVdisc releases at all, as mentioned in this talk page under the WORM? heading (and in the main article as well), because CRVdisc wasn't really marketed as a consumer format. CRVdisc was mainly a professional/industrial format, due to it's high cost. misternuvistor 21:39, 11 December 2005 (UTC)

Can you play records on one of these things?

I know it sounds stupid, but it makes a fair amount of sense: records and laserdiscs are circular, spiral-recorded analog storage methods, and I knoew for a fact there are laser-turntables. So: Can I use my LD player for my LP discs? I know I could find out just by sticking one into the other, but I'm afraid I might break something.

Quick answer: No, you can't. Trying might not break anything, but I wouldn't think of it. Wyss 05:03, 5 Jun 2005 (UTC)

I'm pulling this out of thin air, but a Laserdisc player's laser is presumably only capable of detecting whether there is a hole or not in its path; whereas with a vinyl record it is the shape of the V-groove that encodes the sound, and at the very least I imagine you'd need two lasers to determine the shape of each side of the groove, and you'd need to be a technical genius as well (waves hands). Science! -Ashley Pomeroy 21:54, 26 August 2005 (UTC)

There are laser turntables that play vinyl records but any similarity ends there. :) Wyss 00:55, 27 August 2005 (UTC)

You may have more luck with a CED player, since I think those actually read a groove like LPs...but, I think even with that you won't have any luck. -Gregg

A CED player isn't capable of playing phonographic records (LPs) at all, since CED's similarities with LPs end with using a needle in the groove. CED has a vastly increased density of grooves on the disc, with 9,541 grooves per inch, compared with the LP's groove density from anywhere from 75 grooves/inch for old 78 RPM records, 300 grooves/inch for 33.3 RPM LPs, and 700 (IIRC) for 33.3 "microgroove" LPs. Plus, CED relies on capacitance differences picked up from the bottom of the groove (possibly done by vertical cutting of the grooves during mastering, or pits at the bottom of the groove) using a special electrode-fitted stylus, with no vibration of the stylus involved, while LPs solely rely on picking up mechanical vibration from the groove moving in both vertical and lateral directions, with a standard electrode-less phonographic stylus, with no capacitance involved. misternuvistor 19:57, 10 December 2005 (UTC)

I see this is an old question but a quick anecdote. I work for a school district and several years ago someone stole one of the LD players. Later, some dude brought it in a pawn shop and said it didn't work - and he was trying it with an LP! (The pawn shop gave it back to us.) 72.87.188.145 08:11, 10 October 2006 (UTC)

Accessing analog LD tracks

Hello and Help !! I have two perfectly working philips vlp-700 Laserdisc players (these are part of my classic AV collection) which I’v restored. I have a few discs which play no sound as they are Dolby Digital (all I get is a hiss both L&R) I know the players are analogue only. I know that somewhere on the discs is a Mono analogue signal. anyone know if this signal will be present outside the realms of the laser detection components. If so can it be taped into to get the mono sound track at any quality ? Any advice would be great. Regards Steve

Well, most newer LD releases always have at least one analog track available for playback (either the film's soundtrack itself, or a director's commentary on some discs), which is usually one of the analog stereo tracks (usually the Right channel, IIRC), for compatibility & playback on older players like your VLP-700s. (with the other analog track, usually the Left channel, being a modulated Dolby Digital stream). So, it should be accessible by your player. Is there is a control on your remote for the player (if it has one) to select the audio track to be played? My Pioneer CLD-1010 can be switched to play back either the Left or Right track by itself "duplicated" in both L&R channels. Maybe your player behaves in the same way? misternuvistor 19:29, 10 December 2005 (UTC)

Also another issue: if I'm not mistaken, the VLP-700 is a PAL-standard player, right? If so, this might explain things a bit more: PAL standard LDs only have one pair of audio tracks available (analog only for older LDs, and digital only for newer PAL LDs), while NTSC discs have 2 pairs (4 in all) of audio tracks (one pair analog, the other pair digital). This is because PAL video takes up slightly more bandwidth than NTSC on an LD, resulting in only enough bandwidth leftover on a PAL LD for only one pair of audio tracks. So, the only solution there would be only to play older analog-soundtrack PAL discs, that is, if your VLP-700s are PAL players. misternuvistor 21:28, 11 December 2005 (UTC)

WORM?

Just being a stickler for accuracy here, but first, notice that the following line is apparently missing the first part of the parenthesis:

    "CRV discs existed as both pre-recorded releases and also as blank media that could be recorded once WORM, like CD-R) on each side."

Now, as for the reference to WORM. Technically, "CD-R" discs are not WORM technology in that they can only be written to once. If the CRV discs are truly "like CD-R discs" and can only be written to once, then the WORM reference should be removed. However, if the CRV discs are truly WORM technology, then the reference to CD-R should be removed.

Just my $0.02. Thanks.

--Gregg

Actually, WORM means "Write Once, Read Many", so CD-Rs are a WORM system. The WORM reference here would thus not be incorrect, but the phrasing is redundant. --Scott

Duh. I think it's funny when he said, "CD-R discs are not WORM technology in that they can only be written to once." That's like saying, "CD-R discs are not Write-Once; Read-Many technology in that they can only be written to once." Ha. Thanks for making me laugh. - Theaveng 15:48, 11 October 2007 (UTC)

Gregg Scott Theaveng's right. Yeah, try saying that without larfing ;) CD-R does allow for writing multiple times. - When you do not close the session but leave it open to finish later. This is not recommended! - When you are making a multiple session disc. Where each session is closed and an updated filetable is written to the disc. I had a job that weekly entailed a procedure of performing incremental backups using a Philips 2x writable drive (this weekly ritual became my Coffee Fetching & Consumption procedure.) At any rate a CD-R will always remain readable many times, until the disc becomes unreadable .... such as from scratches made by the unglazed bottom ring of a...... coffee cup! --Mikkel (mibm@tdcadsl.dk) 83.73.92.144 (talk) 00:56, 9 March 2008 (UTC)

"Pre-recorded CRVdisc releases"...

I've removed the reference in this article to pre-recorded CRVdiscs, since this seems doubtful, due to not finding any info about such on the internet via Google (save for mirrored Wikipedia pages). Plus, CRVdisc was not marketed to the consumer, it was mainly a professional/industrial product due to it's high cost. So having pre-recorded CRVdiscs available (as if CRVdisc were a consumer product, which it was not) would seem a bit dubious, IMHO. misternuvistor 21:47, 11 December 2005 (UTC)

CRV...

I have also removed the CRV reference in the second paragraph:("Sales began on December 15, 1978 after the earlier CRV (Component Recordable Video) disc format had died out in obscurity."). AFAIK, there never was a "CRV" videodisc format that existed before DiscoVision/Laserdisc. There was the earlier prototype laserdisc system that MCA Disco-Vision introduced in 1972 at a press-showing that was referred to as the ROVS (Reflective Optical Videodisc System) that would later become the DiscoVision/LD format, but it was never referred to as CRV (and it wasn't recordable as that TLA implies), from my knowledge and research on the internet and elsewhere (especially here [4], a page about DiscoVision's history). Of course, there is the CRVdisc format developed by Sony (as I have mentioned about earlier in this talk page), but this was developed in the 1980s, long after DiscoVision/Laserdisc was released. misternuvistor 08:47, 13 December 2005 (UTC)

Recordable laserdiscs.....

I am removing the passage in the 2nd paragraph in the "Success of the format" section concerning recordable LDs ("Nonetheless, the recordable Laserdisc format was kept off the market to prevent high quality copying"), because of it's vagueness (which recordable LD format?), and due to the fact that there wasn't a recordable LD format that ever was "kept off the market" to begin with. Sure, there were recordable formats allright (such as CRVdisc and Recordable Laservision (RLV)), but they were simply too specialized, and too expensive to manufacture to ever be even thought of being marketed as a consumer format, only at a more professional/industrial market that could afford it (the cost to manufacture any recordable optical disc format in the 1980s heyday of the LD was simply quite high, due to it being such an very new technology). I don't think piracy was the reason.

I'm also removing the phrase "recording-capable units were not sold to the general public due to pressure from the film industry" in the 4th paragraph of the "Laserdisc vs. VHS" section, because once again, they were not sold to the public due to their high cost of manufacturing them instead, due in turn to being such an extremely new technology (recordable discs like RLV and CRVdisc, that is). It had nothing to do with piracy, or the film industry (I'm sure the film industry didn't pay too much attention to LD to begin with. They had bigger fish to fry, namely VHS and Betamax :) ). misternuvistor 01:58, 23 January 2006 (UTC)

I'm adding this back with more neutral phrasing, you two's objections of my lacking any evidence for sinister motives on the part of content providers and equipment manufacturers are neatly counterbalanced by the fact that you lack any evidence of recordable laserdiscs being inherently expensive at the time. Instead, all you can produce are dubious price extrapolations from the cost of recordable LD technology and media's microscopic production runs of the time, and vague statements of "it was really new!" (as if Laserdiscs themselves weren't at first :-p).

Whether or not you believe recordable LDs would have succeeded in the marketplace, the entire article should at least avoid contradicting their very existence and ignoring the possibility of their success. 207.177.231.9 16:44, 20 July 2007 (UTC)

Basic Specifications

How about a list of some basic specifications, in a simple form, with things like when it came out, how much they hold, etc. --202.164.193.221 21:13, 1 March 2006 (UTC)

I am going to get to that sooner or later, but sometime within the next five days within the date of this posting. As informative as the article is, with the introduction of the "CAA" information several walls of text need to be broken into subsections and other discrete subcatagories within the article. In gerneral, its time to clean-up this article.

The section most in need is "technical specicfication" which I plan to modify by adding software and hardware subsections. I will encourage other, more knowledgeable people to add subsections to "success of the format" as well as its comparisions with completing formats during its existance.--Caesius 22:23, 1 March 2006 (UTC)

Transparent vs. Reflective mode?

"By 1969 Philips had developed a videodisc in reflective mode, which has great advantages over the transparent mode" -- such as?

What are these two modes? It's never explained. —The preceding unsigned comment was added by Navstar (talk • contribs) 19:59, April 16, 2006 (UTC)

I would assume this means how the disc operates. But I've never ever heard of a transparent mode disc. All discs are reflective... Nil Einne 14:37, 12 October 2006 (UTC)

The Laserfilm system was transparent. The advantage of the reflective disc is that it can have two playable sides, the transparent disc has only one. --Blainster 08:02, 29 December 2006 (UTC)

LD pressing

"both players and software are no longer produced"

Certainly not in the US, however, I have read somwhere that the is at least one place in the world where LDs are still being pressed. Since they were still being pressed in the late 1990s, and that the pressing facilitys would have been comercialy availible, there surely must still be some surviving (if not operational) pressing equipment somewhere.203.214.75.127

Unfortunately, the article is correct in regards to both hardware and software no longer produced. I have no idea as when the last Laserdisc player was made but laserdisc production ended sometime in 2001 in Japan and facilties were converted to DVD production. By several credible accounts, Japan was the last hold out in Laserdisc support.

With the end of support and major financial investment in the machinery of Laserdisc production, I believe it all to be moth balled in the warehouses of these major corporations.--Caesius 17:22, 6 January 2006 (UTC)

Which came first?

Something just struck me while reading the "audio" section of this article: which was offered to the public first, a Digital Audio Compact Disc or a LaserDisc with digital audio tracks?--Kenn Caesius 15:30, 23 June 2006 (UTC)

Well, AFAIK, commercially (and with the exception of the PCM adaptors which came out shortly beforehand, which were more of a prosumer-market technology then), Compact Disc was the first digital audio format available to the public in 1982 staring in Asia, however, Sony, Philips and DiscoVision (along with Pioneer) did develop some experimental digital audio formats in the late 70's using LaserDisc. These experiments used the whole video bandwidth of the disc (much like how the previously-mentioned PCM adaptors operated wih videotape), instead of a more efficient separate FM-modulated subcarrier (containing PCM audio data) riding alonside the analog video and audio carriers, which what all commercially-released LDs with digital audio tracks (aka, discs & players with the "Digital Sound" logo) like you mentioned, use. Sony and Philips referred to this early experimental format as a DAD (Digital Audio Disc), (IIRC, don't quote me on that), and their work on this format (which never made it out to the market) formed the foundation for the development of the Compact Disc later on.

The first laserdisc player to have "Digital Sound" capability (as well as the first LD player to have audio CD playback capability) was released by Pioneer in 1984, 2 years after the introduction of CD (I forget which model number, I think it was a CLD-series player, though).

Here's a link to a page mentioning one of these prototypical LD-based "DAD"-type discs, this one developed by Pioneer & DiscoVision... misternuvistor 07:03, 26 June 2006 (UTC)

I think the nomenclature gives it away. Compact is a relative word, as CDs are bigger than the cassettes they replaced, so they were likely comparing the "compact disc" to a bigger optical disc. Ham Pastrami 05:12, 31 May 2007 (UTC)

The Last Laserdisc

As a useful trivia point, I think it would be good to mention the last movie released on laserdisc. Does anyone know what it is? -Litefantastic 20:55, 5 July 2006 (UTC)

Such information is already mentioned in the "History" section of the article.--Kenn Caesius 02:30, 6 July 2006 (UTC)

removed Twin Peaks

The version of the Twin Peaks pilot that existed on LD was not in fact the version aired in the States, but the "movie" version produced in case the show failed to air in the UK. Since this is an obscure, secondary version of the pilot and not the one sought by fans, it sort of seems less relevant (than as written) so I removed the mention entirely.24.33.28.52 20:02, 14 July 2006 (UTC)

Storage Capacity math

Since a normal CAV 12" disc can hold 54,000 still images, would that add up to 47GB of storage? (640 × 480 × 24bitRGB = 900KB) × 54,000 frames = 48600000KB / 1024 KB per 1MB = 47460MB = 46GB

--Navstar 06:38, 1 September 2006 (UTC)

Not quite. The signal to noise ratio isn't good enough to support 24 bits per pixel - plus the Hf response isn't great - additionally the color carrier only has a response of 1/4 the resolution. Basically you end up with:

video = (assuming approx 4 Mhz bandwidth) at 6 bits resolution = 3 megabytes a second or 100 k a frame x 54,000 = 5.4 gigabytes

audio = 275 megabytes (digital audio tracks) + 170 megabytes (encode DD on both analogue tracks)

Total is = 5845 megabytes.

Although you could probably cut that by 50% once you included any error correction to cope with drop outs / noise on the video track. A laserdisc size DVD would be much more interesting. Megapixie 07:01, 1 September 2006 (UTC)

How about laserdisc-sized Blu-ray Disc? On a later note does anyone know the capacity of these disks? Like 1 GB or something? Thanks in advance. Josh215 20:40, 12 March 2007 (UTC)

I feel the need to mention, just in case anyone is unclear, that LaserDiscs are analog. Their video is also completely uncompressed. Try recording 30 minutes of uncompressed video onto a computer and see what that gets you (it varies a bit, but still). I'll just say it's a lot more than 5845 megabytes. Point is, you can't accurately compare analog and digital storage. They're too different.

Laserdiscs and Super VHS tapes have a lot of commonalities. They store better-than-broadcast quality video, with a bandwidth of 0 to 7 megahertz. That said, when you use a Super VHS tape to store ADAT (digital audio) or Digital VHS video, you get about 12 gigabytes per hour of tape, and I suspect if laserdisc was somehow converted to store digital information, you'd get the same amount... around 12 GB per hour (per side). ----- Of course since laserdiscs are not digital, but analog, you'd have to use some kind of modulation (representing bits with sounds). - Theaveng 15:50, 11 October 2007 (UTC)

Market

Could someone try and write a section (or at least a few sentences in the introduction) on the international market for Laser Discs - I've never even heard of them before! Rogwan 21:19, 10 April 2007 (UTC)

No mention of Karaoke?

To my knowledge, Karaoke was the real impetus for adoption of the Laserdisc, primarily in Japan and as something of a fad in North America. Nearly every Laserdisc player has microphone inputs for this reason, a feature rarely found on commodity VHS or DVD players. The article doesn't seem to make any mention of Karaoke though. Ham Pastrami 10:05, 29 May 2007 (UTC)

Dumb question

I've got a Laserdisc player, with a flap that opens inward. How do I load discs? -RestlessPegLegSyndrome 03:56, 15 July 2007 (UTC)

Sounds like a CED player, which uses records sealed inside a plastic caddy. The door opens inward, and then you insert the whole caddy into the machine (similar to how a floppy disk is inserted into a computer). - Theaveng 12:45, 10 October 2007 (UTC)

Luminance Bandwidth??

I have looked and looked and looked, but I can not find a source to answer that simple question. Is it 5 megahertz? Someone should add the answer to the article, if it's available. - Theaveng 12:45, 10 October 2007 (UTC)

VHS vs. LD, "air bearing", etc.

Although there is indeed an air bearing in normal operation, this (along with tape tension) is far from perfectly maintained and there is some contact, particularly during spin-up and spin-down times. Furthermore there is no air bearing at all on the control head as it is not on the drum... please note that the article does not specify "spinning", hence this is a valid interpretation. Additional details on the fine points of VHS machines really belong in the VHS article, not here. Jeh (talk) 15:51, 20 November 2007 (UTC)

The tape is not in contact with the drum when it is spun-up or spun-down. The drum starts spinning first. And then the tape is threaded around it second, so the air bearing is always present. ----- As for the control head, it would have some minor contact on the tape edge. That's true. But it would not degrade the actual picture. ----- As for these details not being in this article, my main concern was to get the facts straight. No point in making the LD v. VHS comparison if the comparison is invalid (i.e. claiming the playback/record heads rub the tape). - Theaveng (talk) 16:55, 20 November 2007 (UTC)

The control head contacts the tape across its full width. There are only gaps on the edge, true, but the width of the head unit (like that of all of the rollers, etc.) is that of the entire tape, so there is contact (scraping!) across the full width. And yes, the heads on the drum do contact the tape at times. If not, then why is cleaning sometimes necessary to remove shedded oxide from the gap? Jeh (talk) 17:59, 20 November 2007 (UTC)

Cleaning? What's that? I've never needed to clean my Super VHS vcr; just because they sell such items in stores does not mean you "need" them. They also sell undercoat protection at stealerships, which is totally un-necessary (the manufacturer already undercoated the car in the factory). But you make a good point about how the control head scrapes the tape as it crawls past, which is something I had not considered. - Theaveng (talk) 21:25, 20 November 2007 (UTC)

Yes, the cleaning TAPES are useless. That doesn't mean cleaning is useless. Any decent tech will manually clean (with swabs and similar materials) the tape path and heads of any machine entering the shop. They're going to play very expensive alignment tapes on the machine and they can't risk gumming up those tapes with the residue that might be on your machine. Jeh (talk) 17:43, 21 November 2007 (UTC)

Ah, I did a bit more research (I called a friend who's a master VCR tech). It's worse than I thought, and much worse than you thought. The air bearing does exist... but it's there to prevent contact between the tape and the overall surface of the drum, which otherwise would result in very high friction. The tips of the heads however protrude slightly from the spinning drum diameter and are in "intimate" contact with the tape AT ALL TIMES during normal operation. If they weren't, not only would they not need cleaning, they also would not wear out. But, they do, and they do, and they do wear into the tape surface.... so, there was no "making up lies" here. Jeh (talk) 18:21, 20 November 2007 (UTC)

And I might as well add that degradation of the control track most certainly CAN degrade the picture. The control track is where V sync comes from. If it's too weak the TV will never achieve vertical sync and the picture will roll forever. I suggest this definitely counts as degradation. Incidently this concept is not new with VHS. Way back when I was working with Ampex 2-inch quad machines, one of the adjustments was the head "tip"... how much the heads protruded and thereby how much they contact the tape. More "tip" meant better PQ but faster head wear. Jeh (talk) 18:31, 20 November 2007 (UTC)

My VCR makes it's own V-sync to stabilize tapes (and also live TV channels).

Yeah, I have a pro machine with so-called TBC too. It will stabilize the sync. It can't generate it from nothing. Jeh (talk) 17:43, 21 November 2007 (UTC)

Actually TBCs *do* generate sync. That's one of their primary functions. - Theaveng (talk) 20:46, 21 November 2007 (UTC)

A TBC cannot generate V-sync from nothing. Well, it could, but the result would be wrong 524 out of 525 attempts. The TBC circuit in such VCRs cleans up and stabilizes the signal from the source. Jeh (talk) 00:57, 22 November 2007 (UTC)

Anyway. If your master tech says the VCR heads scrape the tape, then I guess we have to trust his judgment, but I still have my doubts he really knows what he's talking about. (Translation: I want to see a citation that the play heads touch the tape.) I've torn-apart VCRs and the heads are flush with the surface of the drum. Plus: I'm still using a tape that I bought in 1985 with my first VCR & use as a semi-daily time shifter... I don't see any visible "scrapes" on the surface of the tape even after thousands of uses. If the master tech was correct, I should be seeing lines streaking across the tape; and I don't. - Theaveng (talk) 21:25, 20 November 2007 (UTC)

Well, here's one citation:

http://www.patentstorm.us/patents/5543990-description.html - "The configuration of projecting portions of the head tips, and the curvature thereof in a direction transverse to the tracks are optimized for uniform contact with the magnetic tape."

And another: http://www.freepatentsonline.com/5543990.html - "The head tips are held in good sliding contact with the magnetic tape for better recording and reproducing characteristics."

and another: http://www.sparkysworld.co.uk/vcrs.htm - "Placing the gap in contact with the sensitive surface of the tape causes the magnetism to be transferred to it."

and another: http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel1/20/4499/00179555.pdf - "VHS-VCR requires a tape having an MD stiffness of more than 250 mg in order to establish an optimum head-to-tape contact ."

I think that should do... Jeh (talk) 17:45, 21 November 2007 (UTC)

I am nonplussed at your edit to the article after I gave here the citations to the contrary that you asked for. This does not seem like a good faith effort on your part. Come now, be a man and admit you were wrong. Jeh (talk) 00:57, 22 November 2007 (UTC)

Laserdisc vs. DVD, analog vs. digital

I have once again corrected the following claim:

" The variable quality of analog media are theoretically capable of higher quality than the fixed quality of digital A/V carriers such as CD and DVD (example: ED Betamax produces over 500 lines of resolution, while DVD is commonly reported as only 480 lines by manufacturers). "

One: no, there is no inherent advantage (or disadvantage) of analog over digital, assuming that the basic specs such as analog bandwidth (resolution) and signal to noise ratio are the same. Please see Nyquist, Shannon, et al.

Two: The example given of ED betamax over DVD is irrelevant, because the basic specs are different. It is obviously possible to show opposite examples: digital media with far superior performance to analog. But if you match the basic specs, and if lossy compression is not involved, then the performance will be the same.

The LD/DVD issue is confused because lossy compression IS involved on the DVD side. But this has nothing to do with "digital media." It has to do with the storage and processing requirements of lossless-compressed video, which made it impractical to use such on a DVD-sized disc. Please, don't make this into an analog vs. digital (or head contact vs. air bearing) war. Jeh (talk) 02:21, 11 January 2008 (UTC)

You are correct. I have eliminated the phrase "analog media" and "digital media" to focus on the Laserdisc versus DVD comparison. ----- BTW digital media is not perfect. If you take into account the Kell factor (~0.8 horizontal), that reduces resolution. As does the lossy compression (which you mentioned). ---- Theaveng (talk) 13:17, 11 January 2008 (UTC)

An excellent rewording. Thank you. Jeh (talk) 00:26, 12 January 2008 (UTC)

I never said digital was "perfect", nor is perfection required here: Only that the claim of inherent superiority due to analog's "continuous" nature is unfounded. A digital signal chain with a given bandwidth (Flow, Fhigh, tolerance) and SNR will, within that tolerance, reproduce any signal that an analog chain of similar specs can reproduce - and, of course, vice versa. Jeh (talk) 00:26, 12 January 2008 (UTC)

BTW Kell factor is much more about stationary test patterns than real moving images. But even WITH Kell factor of 0.8, DVD's 720 pixels per screen width supports horizontal resolution of 432 line pairs PPH, so LD still doesn't have an edge. Then there is chroma performance, in which DVD is far superior, although again because of digital compression and 4:2:2 sampling and all that, it is different and difficult to compare directly. Nevertheless DVD can usually "resolve" details across a horizontal line that differ only in color much better than LD can. Jeh (talk) 00:26, 12 January 2008 (UTC)

A DVD at 432 lines (not pairs) would be only slightly better than laserdisc's 425 lines. If that DVD has been compressed to squeeze more video into 4.5 gigs, it's measurable resolution might fall below 400... inferior to laserdisc. (Overall the best format was actually ED Betamax with over 500 lines.) ---- Theaveng (talk) 20:33, 14 January 2008 (UTC)

Damn! I can't believe I made that "line pairs" goof! I know better, and I've even quoted the relevant part of the RS-170 specs at people who didn't believe that "tv lines" counted both the white and black lines, unlike photography's "line pairs"! Argh. Thanks for the gentle correction. Anyway, yes, very true. On the other hand, as the article states, LD performance isn't always right at the edge of the spec either. And very few images need that much detail everywhere at once -- the whole point of the compression algorithms is that they can put the bits where they're needed. And sometimes they do too much of that, or they do it too sloppily, resulting in blockies... Jeh (talk) 20:52, 14 January 2008 (UTC)

I hate blocks. On one of my DS9 dvds, there's a dark scene lit by a fire. The fire looks like it was made from orange-colored Legos instead of a natural plasma.  :-( I wish the engineer had spent more time cleaning that up. ---- Theaveng (talk) 13:03, 15 January 2008 (UTC)

Fair use rationale for Image:PILF-2193.jpg

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BetacommandBot (talk) 00:57, 14 February 2008 (UTC)

Laser rot

It says in the article that a citation is needed to account for the statement on the rot of some of the early LD discs.

There is an excellent discussion mainly on this topic that took place in 2003 here: [5]

It also has one contribution from someone who has rot on his LD of the Clint Eastwood film Unforgiven issued by Warner Brothers - which dates to 1992 (which may or may not be the year of the production of his LD copy). Now this would indicate that some production plants still (1992-ish) manufactured discs that would develop laser rot in as little as 10 years, before 2003.

Not to confuse the concept laser rot with a similar defect found with some DVDs, the laser rot on LD occurs because some humidity was trapped between the sandwiched layers of the LD. While the DVD rot is a different beast, by which the discs aluminum surface is contaminated and develops corrosion. Both may render discs unplayable. Or affected audio tracks that are digital beyond listening while the analog audio track remains less affected. One of the benefits of the LD format is the level of backward compatiblity which enabled both digital and analog versions of the soundtracks on many discs. Although the NTSC format would allow for ocasional mastering of alternative audio track such as commentr on the analog audio track, it may make a film viewable one last time, or perhaps at a transfer to VHS, which - all faults aside - is a slightly more viable media, being entirely analog and not suspectible to the mares of the digital rot.

I do not know the etiquette and protocol of what constitutes a reliable source for a citation, but the discussion is made several years ago and remains quite sober and informative, and also gets around other subject of life with LD, offering an insight into the wealth of knowledge several of the contributors of the discussion has on the matter of LD.

As a newcomer to the LaserDisc format myself - I reckon have owned 8 films for less than 36 hours at time of writing as very new - reading the discussion linked to above left a very positive impact on me. Also I have owned a nice working Pioneer CLD-D515, unfortunately wo the remote, for little over half a year with no way to test it until now.

83.73.92.144 (talk) 00:21, 9 March 2008 (UTC) -Mikkel (mibm@tdcadsl.dk)