FACTOIDS: LASER & MEDIA ISSUES (DVD9 Added)

[charlie_ps2]

I've reposted and update this info as many new members won't have seen it and there is some new info since it was first posted.

Many people think that burning CDs at 1x or 2x is best; others report good results at higher speeds. Here is something fairly technical that I hope you find useful.

I'll use Verbatims as the CD-R example. They come in three subtypes within two types of photosensitive dye:

Cyanine
Datalife Plus
Metal AZO

Pthalocyanine
Datalife

Cyanine CDs have a Long Write Strategy and so burn best at 1x or 2x. They have a longer shelf life if exposed to light, especially AZOs.

Pthalocyanine CDs have a Short Write Strategy and so burn best at 4x or on the best burners 8x (Laser power matters at higher speed). They have a shorter shelf life if exposed to light - say 10 years.

With CDRs it's all about ensuring that the burned opaque bit doesn't splay so as to make it difficult to read; burn a Short Write Strategy CD-R for too long and that's what happens. Pressed CDs have clean pits and ridges and it's the transition from one to the other that counts as a 1 bit.

A CD is written/read along a spiral groove which is tracked by the laser. Light is reflected back to the laser's optical diode and phase difference is measured between sent and received light.

Plextor & Yamaha (and possibly other) CD burners use a mechanism called Running OPC to vary laser power and speed according to information decoded by the reflected light coming from the groove. The aim is to make the opaque burn as clean and unsplayed as possible, thus making the CD-R the closest in optical behaviour with a pressed CD. With such burners, it is possible to set a higher speed than what has been suggested above because appripriate (more) laser power would be applied at the higher burn speed.

Bottom Line
If you were aware of the above and burned at the said speeds, then you would be satisfied with the results. PC World (UK) "unbranded" media are the same fabrication as Verbatim Datalife (except that Datalife have better surface protection), and these both are the ones I rate best.

As ever, my advice is taken at your own risk!!

[charlie_ps2]

A question asked on another forum about the function of the white cog led to some research by my famous 'mate round the corrner'. This is what we found.

This wheel adjusts the angle between the rails that the sled runs on and the disk itself. The rails should be parallel with the disk surface. When a new disk is inserted the laser does a process called 'focus search' where it moves the laser assembly up and down until the best (minimum spot size) is found. This is then used for the whole disk, but, if the rails are not truly parallel with the disk, focus will deteriorate as the laser moves away from the initial position (the inner most tracks). That is, the laser will be closer or further away from the disk at the outermost track positions and either is bad news.

So I can verify that the adjusting the white cog does have an effect and if it was set wrongly to begin with, by Sony, then you can improve things by adjusting it.

We tried with a machine that is in for a new laser assembly and got things very slightly better using this method, but not perfect. The new laser unit was fitted and behold, it worked first time without any tweaking.

So this is a 'fringe' adjustment; as the laser reaches the end of it's useful life, you MIGHT be able to squeeze some more life from it using this method.

The available adjustments therefore are:

Intensity (ohms/pot adjustment)
Azimuth
This method, let's call it Parallax.
Lens cleaning
Disk cleaning

This advice is provided at your risk.

[charlie_ps2]

General Information
As with CD-R, DVD-R/DVD+R (DVDR) uses an organic dye polymer that reacts to around 10 milli-watts recording power. Because DVDR holds around 7 times CD-R capacity the laser wavelength is shorter (650nm red against 780nm infrared) and the DVDR recording lens has a nominal aperture of 0.6 against CD-R of 0.5. These two factors combine through the higly focused red laser beam to produce opaque burned marks as small as 0.44um as compared with 0.83um on CD-R.

The dye polymer is coated onto an optically clear polycarbonate substrate that has a microscopic groove (known as the pre-groove), 650nm deep, formed as a spiral track across the surface. Behind that a thin layer of reflective metal is sprayed and then optically clear protective layers are applied to form the disk that we see.

For recording, the tightly focused (on the pre-groove) laser beam heats the dye polymer, permanently altering its state (to opaqueness) such that microscopic marks are formed in the pre-groove, the length of which depending on the time during which the laser was turned on. These marks correspond with the raised portions of a pressed DVD and are thus non-reflective or insufficiently reflective (provided that laser burning power was adequate) to register upon reading.

For reading, the areas between marks, not being opaque, are reflective when a tightly focused laser beam of much lower power at 650nm wavelength is sent to the pre-groove.

Data is then streamed by noting the transition from reflective to non-reflective and the length of time to the next transition. A digital-to-analogue decoder then converts this 0/1 stream to data as we know it

So the critical factors that enable a DVDR to be accurately read (assuming a clean lens) are:
a Sufficient power to burn opaque marks
b Sufficient precision to burn marks of the correct length and with sharp edges
c Good quality dye polymer to enable the above characteristics to apply
d Sufficient precision in the reader to correctly stream what was correctly written
e Sufficient power in the DVDR read laser to meet the reflectivity characteristics of the DVDR

The relevant ECMA standards require the read laser to accommodate reflectivity in the range 45% to 85%. If the media doesn't make it into this range, then there s no guarantee that the DVDR will be readable. Reflectivity is a function of the metallic layer and the optical clarity of the protective layers.

Competing Standards
DVD-R
This format sort of "came first" governed by the formal standard ECMA 279 (http://www.ecma.ch/ecma1/stand/Ecma-279.htm). All DVD-ROM drives are supposed to be able to handle DVD-Rs burned to this standard and thus within the correct reflectivity range. Sony would calibrate their lasers to work within the 45% to 85% range. DVD-R can burn at a maximum of 2x.

Without going into too much detail, DVD-R uses pre-set sector address information that synchronises at write time. This is the reason why burning speed is constrained to 2x because this has to be read and synchronised.

DVD+R
This is a competing standard backed by Philips, HP, Sony, Yamaha and Ricoh. The essence of DVD+R is its first incarnation as DVD+RW (ECMA 274 http://www.ecma.ch/ecma1/stand/Ecma-274.htm). DVD+RW uses a wobbled groove the count of which replaces the DVD-RW sector address synchronisation during the burn process. DVD+R is the write-once version, also with a polymer dye so that the burned result is narly identical with DVD-R. The "nearly" term reflects the fact that newer read laser mechanisms are more accurate and can resolve the small differences between DVD-R and DVD+R arising from the fact that DVD+R can be burned at 2.4x because of the wobbled groove.

This means that DVD+R can theoretically be read on any PS2 with a good quality/condition laser, such as the v5 and it has been reported as successful on a v3 - though not many v3s these days have new condition lasers!

As ever, this information is provided at your own risk to use.

[charlie_ps2]

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 medias 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 so as to focus the laser beam tightly to a given spot. There is a number printed on the side of the laser unit that states the amount of current utilised to deliver that beam for the particular laser diode.

Dealing just with the DVD laser diode, this means if the laser can draw c. 500mAmps (I think that's the value) for the red laser beam, then a DVD (or DVD-R) with reflectivity in the range 45% to 85% will be effectively read and processed by the firmware. Indeed a new PS2 laser can resolve Princo DVD-Rs (see below) which have reflectivity below 45%.

An important point to note: Laser Azimuth adjustment (the screw that angles the lens on the sled assembly) can be sloppily set by Sony as there is more tolerance when reading pressed CD/DVD. If the angle isn't right for DVD-R, then reflectivity will be poor because of deviation. So look at that question (separately posted).


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 or Traxdata 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 recalibration 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. Also, like a light bulb, it is always ON when a disk is in the tray.

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 recalibration 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
The PS2 Laser unit is governed by the combination of media and laser calibration/adjustment (assuming the lens is clean). The standard calibration should do for all pressed media and good quality backup media. The physical adjustment aspects, particulary laser azimuth, sometimes need attention when backups won't play (assuming the modchip is correctly installed).

Many users experience greater noise from the laser unit when playing less than ideally produced PS2 backups. Logically, if the laser unit is working physically 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 playng 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.

[charlie_ps2]

I would like to make what I hope is a definitive statement on DVD9.

DVD9 CHARACTERISTICS
DVD9, being dual layer, has low reflectivity as compared with DVD abd DVD-R. According to my information it scrapes through at around 40 to 45% whereas DVD is in the range 65% to 85% and DVD-R in the range 45% to 65%. This low relectivity is necessary to allow light at a different frequency through to the second layer.

So DVD9 operates at one end of laser capability, stretching it to read especially in older units.

DVD9 MOVIES
Many movies are dual layer and play across the PS2 range. There are no complex protection checks associated with DVD9 movies and, if your laser is in reasonable condition, they play without too much difficulty.

DVD9 GAMES
I specially bought Xenosaga so that I could research this for you demanding people.

DVD9 games conform to Sony's special protection check which is a complex algorithm based on a sequence stored in a data wobble deliberately pressed into the groove at the start of the disk.

This deliberate aberration has to be focussed and read in via the laser and this is where, I believe, the PS2 laser has difficulty at such low reflectivity.

We recently chipped a couple of PAL V5s with genuine Magic 2s. They booted Xenosaga first time every time.

When we chipped a US v7 (with any of genuine Magic 2, Magic 2 clone, Apple), Xenosaga would load 1/5 or worse times from the RESET button (usually going to the browser or red screening in the browser).

However we had 100% success booting Xenosaga behind AR2/GS2 v2 without codes. This worked because the groove wobble has been passed OK on the AR2/GS2 disk and when Xenosaga loads, it is handed over to the PS2 at the next stage in booting.

So I hope this clears it all up for you. DVD9 is not affected by the no-swap modchip so far as I have been able to discover.