Talk:DualDisc

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[edit] How can it be possible?

How do they do it? The data layer on a CD is beneath its printing area. The DVD's data layer is sandwiched in the middle of two polycarbonate layers of half the thickness. How do they combine the two physically incompatible formats?

 Side A surface
---------------- CD data layer
                   0.6 mm
---------------- DVD data layer
                   0.6 mm
----------------
 Side B surface

Possibly you can build a CD/DVD hybrid disc that is readable only from Side B:

  • CD: laser -> side B -> DVD (semi-transparent) -> CD data
  • DVD: laser -> side B -> DVD data

How do you build a disc "with one format on one side of the disc and the other on the opposite"? Using two semi-transparent layers?

  • CD: laser -> side B -> DVD (semi-transparent) -> CD data
  • DVD: laser -> side A -> CD (semi-transparent) -> DVD data

I don't know if early CD players can ignore the semi-transparent DVD layer in the middle of its optical path. -- Toytoy 00:20, Mar 22, 2005 (UTC)

DualDisc is just a CD and DVD stuck together. It's similar to making a double sided DVD. The thickness is a compromise, and CD specs can't be met. Mirror Vax 18:28, 11 July 2005 (UTC)

[edit] SACD Comments

I removed the SACD comments because Sony's SACD format does not compete with DualDisc. SACD competes with DVD-Audio. While some record labels might distribute the album with DVD Audio on the DVD side of the DualDisc, it is not a requirement. Sony/BMG just seems to put the album on the DVD video portion of the disc. The SACD/DVD-Audio competition and debate really has nothing to do with DualDisc. --Analogdemon 19:37, Jun 20, 2005 (UTC)

SACD and DualDisc do compete. They are similar products with overlapping feature sets. Mirror Vax 18:23, 11 July 2005 (UTC)
I respectfully disagree. Hybrid SACD as a medium might compete with DualDisc since both can be read by a CD player, but even that's sketchy to me since SACD offers no video possibilites at all, whereas DualDisc with its DVD layer does. In terms of sound quality, there's no competition because again SACD sound competes with DVD-Audio, and while many record manufacturers include DVD-A on the DVD side of a DualDisc, by no means does DualDisc as a medium compete with SACD as sound quality. Just my opinion on the matter. Cheers! --Analogdemon (talk) 17:34, July 28, 2005 (UTC)
Jumping in here late (also I'm new to talk pages so help me out with any etiquette breaches). Hybrid SACD is a competitor. The basic idea of each is to provide both high capacity and compatibility with conventional CD players. DualDisc is more flexible in how that capacity can be used, but high-resolution multi-channel audio is obviously a common case. But as others said below, the level of technical detail on SACD is inappropriate; two long paragraphs and a picture don't even mention DualDisc or DVD. These would be great in the SACD article, but this article shouldn't have more information on SACD than is necessary to understand the difference. --Oldkentuckyshark 06:15, 24 February 2006 (UTC)
You flip it over, it stupid cuz with nornal CDs you cant touch the shiny side, you handle by the printed side, but on these there is no printed sidfe and you can touch either end! That makes em way easier to scratch!@!!!! If Id ever get one, Id copy the CD side to my computers as MP3s and copy the DVD side to a blank DVD-R, Id have 2 seperate discs, but 2 labelled sides! So combining the teo has no appeal to me since Id just seperate them anyways. Maybe if it was Analogdemon said, but then you probablyu couldnt copy at all and I backup ALL cds to MP3! And DVDs too! RealG187 16:40, 12 January 2007 (UTC)

[edit] Article Re-working

I re-worked the article to make it conform to a bit better quality. I included all previous content and added some new content as well. Cheers! --Analogdemon (talk) 15:45, July 28, 2005 (UTC)

Well done. The article is more clear now. I have made some minor changes regarding the specs, and I hope you do not mind. Dsc 18:46, 28 July 2005 (UTC)
I re-worked a bit more, moved your specs to the criticism area since it dealt with Red Book. Also added a small diagram of how the DualDisc works. Cheers! --Analogdemon (talk) 20:59, July 28, 2005 (UTC)

[edit] Relevance of Beethoven's Ninth

Just for the purpose of reaching consensus before removing anything...I personally feel like the comment about Beethoven's Ninth under Criticisms really has no relevance to a DualDisc. Anyone have any thoughts? Cheers! --Analogdemon (talk) 01:42, July 29, 2005 (UTC)

The original CD has a playing time of 74 minutes to cater for Beethovens Ninth. To do so, the disc diameter was enlarged from 11.5 to 12 cm. But now in the DualDisc, since the CD capacity cannot be reached, the Ninth criterion is abandoned, and thus reveals teh industry's opportunistic approach. So I sincerely believe that the remark is relevant. Just like Ohga-san, former Sony president, who first demanded it, I want to hear Beethoven's Ninth in one piece. Dsc 12:14, 29 July 2005 (UTC)

The Beethoven 9th story is apocryphal. In addition, the 60-minute capacity of DualDisc is not a hard limit. It is only a recommended limit. Mirror Vax 14:38, 29 July 2005 (UTC)
I am also of the opinion that the Beethoven story is doubtful. Does anyone have a definitive source for this? Cheers! --Analogdemon (talk) 17:02, July 29, 2005 (UTC)
I re-added a mention of capacity, without mentioning any specific applications. FWIW Ohga may have argued for the largest size that would fit in a pocket, using the 9th (along with "a complete opera") only as an example [1]. It's also possible that all of that was a smoke-screen for some other issue [2]. --Oldkentuckyshark 07:23, 24 February 2006 (UTC)

[edit] Criticms Section

I moved things around and fixed the wording in quite a bit of the criticisms section. It seemed far too complicated to understand. Hopefully I've made it a bit more straightforward. --192.223.226.6 16:59, 29 July 2005 (UTC)

[edit] Goal: Featured Article

I've made a decision to take this article on and attempt to get it to Featured Article status. So if you see tons and tons of edits by me, well, you know why. :) Cheers! --Analogdemon (talk) 02:38, August 4, 2005 (UTC)

[edit] Technical Explainations - Which one is right?

I've reverted Dsc's technical explaination to the previous technical explaination because I believe that is the correct one. However I could be completely wrong. I am basing my explaination solely on the diagram given by the following reference, which, although from a reputable source, is not very detailed. The current explainations is:

Lasers in conventional CD players have a different wavelength (typically around 780 nm) to those in SACD players (650 nm). The hybrid SACDs possess a special high density layer that can be penetrated by the conventional CD player's laser but are reflected by the SACD player's laser. This means that when a hybrid SACD is placed into a conventional CD player, the laser beam passes through the high-resolution layer and gets reflected by the conventional layer at the regular 1.2 mm distance. But when the disc is placed into an SACD player, the laser is reflected by the high-resolution layer (at 0.6 mm distance) before it can reach the conventional layer. To the same point, if a conventional CD is placed into an SACD player, the laser will read the disc without indicdent since there is no high-resolution layer to reflect. There is however a subtle point to be noted, because of the difference between the working distances of CDs and SACDs the aperture of the lens of the SACD player must be adjusted to obtain the correct focal length [3].
  1. ^  Sony Corporation and Royal Philips Electronics, Super Audio CD - A Technical Overview, 2001, p7 bottom-left diagram.

It replaces the explaination:

Objective lenses in conventional CD players have a longer working distance, or focal length, than lenses designed for SACD players. This means that when a hybrid SACD is placed into a conventional CD player, the laser beam passes the high-resolution layer and gets reflected by the conventional layer at the regular 1.2 mm distance, and the high-density layer is out of focus. When the disc is placed into an SACD player, the laser is reflected by the high-resolution layer (at 0.6 mm distance) before it can reach the conventional layer. To the same point, if a conventional CD is placed into an SACD player, the laser will read the disc with no problem since there is no high-resolution layer.

If I am wrong, then I sincerely apologise and please revert back to the above explaination. However I would appreciate a reference to verify the new explaination. I will contact Dsc to ask for his opinions on the matter.

Cedars 09:40, 15 August 2005 (UTC)

The first explaination is saying that the reflective material responds differently to 650nm and 780nm. I don't know if that's correct or not (the source you cited is far from definitive). The second omits that claim and just talks about focus. Mirror Vax 11:24, 15 August 2005 (UTC)
Cedars: The matter on the focal length and the reflective layers is very subtle. The more you read about it, the more you conclude that both play a key role (so both explanations are half correct or half false). Details on the semi-reflective and reflective layer can be found on http://www.daisy-laser.com/technology/techsacd/techsacd07.htm

A quite interesting matter which compounds this matter is that DVD players that are able to play CD-Rs have both an infrared (CD) and a red laser (DVD), plus in fact optics for reading both CD and DVD. It is not clear to me how these players can distinguish between the DVD or CD layer. May be there are cases where the player is playing the low-quality CD layer instead of the high-quality DVD audio. It fuels the notion that audiophiles are probably listening to a CD layer and 'enjoying' the higher quality, but not hearing the difference with the CD quality. May be we should add this difficulty or leave it as it is ? Dsc 07:32, 16 August 2005 (UTC)

I would venture to say that the ability of DVD players to play CDRs holds no relevance to an article on DualDisc. As well, I think the focal length piece should be merged with what we already have since both technical elements seem to compliment each other. In terms of DualDisc, the laser knows the difference between CD or DVD based on what side you place face down into your DVD player. Let's try and keep the technical discussion relevant to DualDisc at some level. Cheers! --Analogdemon (talk) 13:05, August 16, 2005 (UTC)
I agree with you. The dual laser pick-up units and compatibility with dual layer SACD is a relavant matter for the SACD article and not for the DualDisc. Yes, indeed, let us here keep this matter simple. Dsc 16:39, 16 August 2005 (UTC)
I think we should leave the SACD compatibility section as it is. It explains how the SACD is different from a DualDisc. I think that adding any more technical depth would lessen its relevance to DualDisc. I'm going to vote in favor of the status quo. The SACD compatibility section provides just what is necessary to explain how it competes with DualDisc, which is the point. Cheers! --Analogdemon (talk) 17:00, August 16, 2005 (UTC)
I respectively disagree. In my opinion there is currently way too much info on SACD in the DualDisc article. Yes some info on compatible is needed but this should only be brief. The extremely large SACD logo also seems out of place given even the SACD article has a much smaller logo!60.234.141.76 22:07, 5 September 2005 (UTC)

[edit] SACD Logo

Someone uploaded a file to wikipedia with the same file name as my image in the commons, thus why the SACD logo was showing up. I renamed my file in the commons and changed the article to point to the right image. --Analogdemon (talk) 19:40, September 6, 2005 (UTC)

[edit] Double Sided CDs

Are there double sided cds, like two audio sides and no dvd side? If so, are there double sided CDRs? Are there even writable DualDiscs for PC writers yet?


Just copy the CD side and burn to a CD-R and copy the DVD side to a DVD-R! It good cuz you can seperate the teo and have a real disc! RealG187 16:41, 12 January 2007 (UTC)
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