Dreamcast Optical Storage Medium is shit!

[Christuserloeser]

You saved this topic from being moved to The Home of the Jeebaâ„¢.

[|darc|]

The "Technical Information" section of the "GD-ROM" entry in Wikipedia seems to support the OP.

http://en.wikipedia.org/wiki/GD-ROM

Wikipedia isn't exactly the best source for information on Dreamcast-related stuff.

Having worked with GD-ROM dumping projects extensively, I've recovered perfect data from pretty fucked up discs before. As long as you have taken somewhat decent care of your discs and there are aren't many radial scratches, you should be fine.

[cube_b3]

Then can you please point us to a better place because this right here:

Due to the high density nature of a GD-ROM disc, the data layer is very fragile and small smudges and scratches can potentially render a game unplayable.

Supports my claim by 50%, now if I can find something which proves that the black layer CD's offer somekind of durability my hypothesis would be proven.

P.S. what is Constant Angular Velocity, does that say something about making the console stand on an angle?

[DCDayDreamer]

Then can you please point us to a better place because this right here:

Due to the high density nature of a GD-ROM disc, the data layer is very fragile and small smudges and scratches can potentially render a game unplayable.

That's a pretty open statement, it's a bit like saying drinking alcohol can potentially render you unconscious. small smudges and scratches can potentially render any optical media unplayable, it doesn't mean the media is ruined, it means it's been handled and stored badly, a lot of media can be rescued with simple cleaning.

P.S. what is Constant Angular Velocity, does that say something about making the console stand on an angle?

Putting it simply:

The motor that spins your optical media (CD/DVD/GD) operates at the same speed at all times, think about how vinyl is played on a record deck. Don't get confused when the motor stops spinning though, that just means there is no need to read data any more, if there is a need to read data, the motor will spin up again but remain at the same speed.

[|darc|]

Supports my claim by 50%, now if I can find something which proves that the black layer CD's offer somekind of durability my hypothesis would be proven.

You are on a Dreamcast scene website talking to veterans who have been in the scene since its inception. I, personally, have dealt with the Dreamcast's media extensively as part of a disc preservation/dumping project. Any source I can pull up on this topic isn't going to be much more credible than my own word.

Yes, obviously the GD-ROM is higher density, and since the Dreamcast uses basically off-the-shelf optical equipment, it does not surprise me that a scratch to a GD-ROM would harm it more than a scratch to a CD-ROM. BUT... the GD-ROM is still a perfectly durable format and fucked up discs are still often playable. And there's nothing special about PlayStation discs other than the color, which in my opinion was probably only used to differentiate the games from music CDs at a time where the consumer was likely to be confused.

P.S. what is Constant Angular Velocity, does that say something about making the console stand on an angle?

Constant Angular Velocity and Constant Linear Velocity refers to how the motor spins the disc while the lens is reading different regions of the disc. A lens reading from the center of the disc will have data spinning past it at a rate less than if it were at the edge of the disc (think about how bigger wheels on a car will make the car travel a greater distance with one rotation of a wheel). A drive working in CAV mode will have the disc pits designed to be spaced farther apart at the edge of the disc so that the motor can spin at the same speed continuously and the lens will receive the same amount of information no matter where it is. A drive working in CLV mode will have the disc pits placed equally around the disc, but the motor speeds/slows to compensate and the lens still receives the same amount of information no matter where it is.

This has nothing to do with the angle at which the console rests or standing consoles up, which, as quzar already pointed out, is detrimental to the life of the motor. You would do better to open the Dreamcast up, clean its components, and lubricate the drive mechanisms.

[cube_b3]

Alrite thanks, anyway I remembered something cool, the pirate version of Grandia 2 was on 3 Disks where as the orginal is on 1. The entire game basically fits on 1 disc but the FMV scenes have been divided on 3 discs.

[nymus]

Hmm... following |darc|'s illuminating description of CAV/CLV, would it be correct to "clarify" that the method Sega used to increase GD-ROM density was not actually getting rid of the error-correction code as posited by some site(s); that it was retaining the tight CLV-targeted spacing of pits towards the disc edge but for a CAV drive?

This difference seems, at a glance, to suggest that the format is adaptable to PC drives (plextor's GigaRec??) Does dumping of GD-ROM data still require Sega hardware (Dreamcast-BBA/DevBox) or has the GD-ROM format been reversed to work on PC drives i.e., can one burn a cd-r to the GD-ROM 1.2GB capacity and structure?

[|darc|]

Hmm... following |darc|'s illuminating description of CAV/CLV, would it be correct to "clarify" that the method Sega used to increase GD-ROM density was not actually getting rid of the error-correction code as posited by some site(s); that it was retaining the tight CLV-targeted spacing of pits towards the disc edge but for a CAV drive?

A GD-ROM has the same error correction that a CD-ROM has; that is, sectors of 2352 bytes divided into 2048 bytes of data plus 304 bytes of error correction. Removing or reducing the amount of error correction would be too detrimental to the format. The pits on a GD-ROM are more dense than they are on a standard CD-ROM, and towards the end of the disc the density changes to compensate for being used in a CAV drive.

This difference seems, at a glance, to suggest that the format is adaptable to PC drives (plextor's GigaRec??) Does dumping of GD-ROM data still require Sega hardware (Dreamcast-BBA/DevBox) or has the GD-ROM format been reversed to work on PC drives i.e., can one burn a cd-r to the GD-ROM 1.2GB capacity and structure?

Some normal CD/DVD-ROM drives can read GD-ROMs. The problem is that the high density area of the disc (that is, the area beyond the security ring with SEGA's holographic emblem on it) uses a proprietary table of contents format in the bootsector of the high density (first 16 sectors of the high density, i.e. IP.BIN). The CD/DVD-ROM drive does not know how to read this, so it doesn't even know that the high density area is there. GD-ROMs also have a standard density area with a data track (containing some text files and optionally wallpapers and other extras) and an audio track (usually a warning that the disc shouldn't be used in CD players).

In order to read the high density area in a PC CD/DVD-ROM drive, you have to trick the drive into reading a standard table of contents from another disc. So you burn a CD-R with a hacked disc image that has all the specifications of the GD-ROM you want to read. You have to disassemble the drive, insert the swap disc, and swap out for the GD-ROM from the top of the drive unit without invoking the eject function of the drive (otherwise this will refresh the table of contents data). Then the drive will see the high density track and the ISO9660 filesystem and you will see the files perfectly. One problem, though: only a few drive models are known to be able to read the entire high density area; the rest start tripping up towards the end of the disc because of the density changes.

This is why dumping projects just use Dreamcasts with a Broadband Adapter link.

Also, since a GD-ROM drive uses a different physical disc than a CD-ROM, it's not possible to burn a GD-ROM image to a CD-R. It is possible to fit nearly the amount of data that's on a GD-ROM's high density area onto a CD-R using a Plextor GigaRec drive, but this won't be like a GD-R, it will be a GigaRec MIL-CD. So capacity, yes nearly, structure, no.

For the Dreamcast to even start trying to read the disc in its drive as if it's a GD-ROM, it checks the security ring in the center. If the security ring is damaged or missing, it will refuse to even try to see if there's a high density area. No one has reverse-engineered the security ring. It was a piracy protection mechanism like on the Saturn's CDs, to prevent bootleg GD-ROMs from being produced. Unfortunately, Sega left in the MIL-CD format and we learned how to run software on the DC through a different booting scheme altogether.

[Quzar]

Also, since a GD-ROM drive uses a different physical disc than a CD-ROM, it's not possible to burn a GD-ROM image to a CD-R. It is possible to fit nearly the amount of data that's on a GD-ROM's high density area onto a CD-R using a Plextor GigaRec drive, but this won't be like a GD-R, it will be a GigaRec MIL-CD. So capacity, yes nearly, structure, no.

Actually, according to something I don't quite remember anymore, GD-Rs ARE physically the same as CD-Rs but with special stuff in the data header (ATIP stuff) and a GD burner/software could be hacked to ignore that. All the security stuff takes place in the System2 disc. Not having either of these though, and not remembering where I read it, I can't confirm this.

[nymus]

I was about to suggest updating the GD-ROM wiki... too late

My experience with Dreamcast disc quality (someone should add "Dreamcast" to the board dictionary) has been generally positive:

Soul Calibur, the first game I purchased, and probably my most played game is still playable, even with its moderate-high number of scratches. The music does skip, however.

I've had problems with my Sonic Adventure and Street Fighter Alpha 3 discs from the first day I got them but I believe they were from the infamous batch of first presses. http://news.zdnet.co.uk/hardware/0,1000 ... 645,00.htm

My Quake 3 disc has given me quite a few problems but remains playable. First, I was surprised by the number of scratches on it a few weeks after purchase and it eventually would not boot; or would boot but not load a level. This led to my discovering lens adjustment; hence it has now become the disc I use to test that my laser is 'functioning within normal parameters.'

[|darc|]

Also, since a GD-ROM drive uses a different physical disc than a CD-ROM, it's not possible to burn a GD-ROM image to a CD-R. It is possible to fit nearly the amount of data that's on a GD-ROM's high density area onto a CD-R using a Plextor GigaRec drive, but this won't be like a GD-R, it will be a GigaRec MIL-CD. So capacity, yes nearly, structure, no.

Actually, according to something I don't quite remember anymore, GD-Rs ARE physically the same as CD-Rs but with special stuff in the data header (ATIP stuff) and a GD burner/software could be hacked to ignore that. All the security stuff takes place in the System2 disc. Not having either of these though, and not remembering where I read it, I can't confirm this.

Do you have an unburned GD-R? I would be interested to know if the bottom of it looks like it has two separate regions before they're burned. After being burned, they all look the same (since GD-Workshop would pad the second region of all discs out to a 45000 LBA automatically), but before being burned? That would be a decent indicator of whether or not what you're saying is true (and I don't doubt it). On all the pictures I've seen of GD-Rs, and the ones that I have, there are clearly two regions, but it could be that these were all burned already.

[Quzar]

Yea, I can't find where it was (maybe it was over at segakatana) but I distinctly remember at some point reading something that had me thinking that GD-Rs were simply extremely high quality specially branded CD-Rs.

BlueCrab has ... 14 iirc (but no burner =P). It could also be that the difference in density causes light to reflect differently from the disc(just like burned/unburned on a regular CD-R). It might be interesting for someone with a gigarec drive to burn half a disc with and half a disc without and see the difference (if there is one). If a GD-R were to have the same security ring and all that jazz, why the System 2 disc?

[Eviltaco64X]

I have always hated Dreamcast Cd's or GD's they are and were always crap.

In contrast to PS1

Playstation 1 had a black CD storage medium, the black surface would make them immune to scratches or something (to a strong extent) and no matter how weak your lense was an orignal cd would always boot where as pirate cd's would never boot on a weak lense.

I've replaced several PS1 games (THPS2, FF8, Parappa, Ape Escape) at least 3 times due to (other people's) carelessness.

[Eckostyle]

Just package it with a copy of Shenmue 2 for this X-Mas, and everything will be fine.

[FamilyGuy]

Do you have an unburned GD-R? I would be interested to know if the bottom of it looks like it has two separate regions before they're burned. After being burned, they all look the same (since GD-Workshop would pad the second region of all discs out to a 45000 LBA automatically), but before being burned? That would be a decent indicator of whether or not what you're saying is true (and I don't doubt it). On all the pictures I've seen of GD-Rs, and the ones that I have, there are clearly two regions, but it could be that these were all burned already.

There's 2 distinct regions on my own unburnt gd-r. Also, the density the DC reach at the outtermost part of the disc is almost 1.8x (from tech docs), the density increases from the begining of the gd-rom aprt of the disc until the edge, for those who might wanna know.

FG

[cube_b3]

You know I'm completely out of this discussion your technical talk is flying over my head.