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  #1  
Old Aug 11, 2002, 08:09 AM
mozzie mozzie is offline
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Default Understanding DVD/DVD-R & Laser Issues

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Not sure if this has been posted here yet but here is some interesting reading for those that want it.

Understanding DVD/DVD-R & Laser Issues
Success with DVD/DVD-R on the PS2 is, first and foremost, a question of reflectivity and the causes of poor reflectivity.

The exception is (my thanks to Phreaker47 on ISONews for this) a game like GTA3 that is coded to stream data on the fly. Phreaker47 wrote " ...especially when you are driving through the cities. parts of the landscape that are just beyond the horizon are loading without interrupting the action. So, the effects of quality difference in DVD-R media's are exposed here. If there's a "hiccup" in GTA3, you're screwed because you need that data loaded right away or it will interrupt your game. hence, the screen freezing with the message 'Error Reading GTA3 DVD', and the other effect being messed up textures that failed to load properly in this short time window". The v5s are faster PS2s and the effect is far less marked on those models.

Sony calibrate their CD and DVD laser diodes at around 1200 ohms, Dealing just with the DVD laser diode, this means if it can deliver 2mW (I think that's the value) power to the red laser beam, then a DVD (or DVD-R) with reflectivity in the range 45% to 85% will be read and processed by the firmware. Indeed a new PS2 laser can resolve Princo DVD-Rs (see below) which have reflectivity below 45%.

If the laser can't deliver the correct power, like it's near fried, worn out or whatever, then it will only read a DVD (or DVD-R) if there is sufficient power to read a disk with reflectivity higher up the band range. At worst, it will appear to emit light, but at a power lower than can generate a properly reflected return beam.

DVD-Rs have reflectivity in the range (my estimate) 15% to 65% and this is price related. I haven't been able to measure nor discover the reflectivity of Princos, but I estimate below 40%. But I know that Mitsui are 50% and Verbatims around 60%.

So now that you can see what makes a DVD drive sensitive, let's look further under the PS2 hood.

The Laser - does it wear out?
The" Laser" means the Laser Diode, the semiconductor that lases to produce coherent light. This diode is a sandgrain in size reaching 70 deg Centigrade. A very small increase in current (like pushed through by 5v or by over-reducing the resistance using the re calibration pots) will take the temperature through the breakdown barrier so that it lases dark light or weakly lases at the right wavelength. So yes, like a light bulb, the Laser will eventually wear out according to use.

Does a DVD-R wear the laser out?
A cheapish DVD-R has about/less than half the reflectivity of a pressed DVD and the laser power required to avoid re-reads is higher on poor media, achieved by re-calibration. A more expensive DVD-R (e.g. Verbatim) has about 60% ideal reflectivity which, with a clean lens, is sufficient to work with the standard laser power, esp. on a v5. So the laser will wear out sooner if you re-calibrate it and even sooner if you over-calibrate (by more than, say, 10%).

Red Screen of Death
When the disk is inserted, you can hear something akin to a mouse squeaking very rapidly. That's the lens moving up and down to focus and side-to-side to locate the groove that it follows to obtain the data. This lens movement is activated by magneto through tiny wires, current and magnets. Then the sled traverses the disk to measure its diameter (there are mini sized audio CDs).

When focusing, it tries first in red light; if there is reflectivity, the disk is a DVD/DVD-R and it can boot; if it is not a PS2 disk, the red screen appears.

If there is no reflectivity, it tries infra-red light and if there is then reflectivity, the disk is a CD/CD-R; if it is not a PS2 disk, the red screen appears.

If there is still no reflectivity, it goes to the browser. Either the lens is dirty or the laser cannot muster enough power and needs re calibration and eventual replacement.

There is an outside chance that the laser needs adjusting for the lens being parallel to the disk (azimuth) or the sled being parallel (the white cog).

To summarise (adapted from a piece by Fogbank)
The laser unit generally works harder to read any kind of recordable media (CD-R or DVD-R). This can be further complicated by playing "DVD Rips" which are DVD based games that have been downsized to fit onto CD-R. These may not have optimal file layout or addressing, and may cause your laser unit to work even harder to read the data required to run the game.

Many users experience greater noise from the laser unit when playing less than ideally produced PS2 backups. Logically, if the laser unit is working harder, it may wear out, or lose its calibration, earlier than if it were only reading pressed media. The best approach to these issues is to use the best media you can (fewer "re-reads" means the laser unit doesn't work as hard), avoid non-optimised DVD-Rips if you can, burn backups at slower speeds, keep your laser clean, and keep your media clean. Many users have been playing backups on their PS2's for several years now, and are still gaming away. Laser unit wear and tear is, however, the price you potentially pay for playing backups.
  #2  
Old Aug 11, 2002, 08:29 PM
smokafatty smokafatty is offline
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Wow, thats good to know. Bump to the top for the people that haven't read this yet.
  #3  
Old Aug 11, 2002, 09:43 PM
Groggy Groggy is offline
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Yeah, great post - does anyone know why your discs get circular scratches on them?
  #4  
Old Aug 12, 2002, 12:26 AM
Berns Berns is offline
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GROGGY! that happens to my disks I had those protection things from precisionmods.com in my ps2 tray and i think taht is what was causing them, not sure.
  #5  
Old Aug 12, 2002, 12:55 AM
Xcubetion Xcubetion is offline
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What are the best cds to have then?

Princos?,mitsui?,which?

How do you guys rank them from best to worst?
  #6  
Old Aug 12, 2002, 04:57 AM
mozzie mozzie is offline
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Guys, all discs get circular scratches eventually, its to with the disc spinning in the tray, sooner or later when there is too much scratching the laser has trouble reading the disc, thats why its best to keep your original safe and use a backup.
 

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