Technical Information on DVD SL and DL discs

Written by JoeRyan


Comments on the question of recording speeds and media since I have been in the design, manufacturing, and testing business for recording media most of my professional life. The question is whether or not it is advisable to record at the slowest speed for optical media to get the best results. The answer is: it depends.

The "best" speed is the one that provides a recording with the highest signal to noise ratios, fewest errors, and lowest jitter. The rated speed of a disc that matches the rated speed of a drive, particularly a new drive, will give good results if the design engineers created suitable recording firmware for that disc. A 52X CD-R recorded at 52X in a 52X drive will generally be well recorded; and a 16X DVD+/-R recorded at 16X in a 16X drive will also be well recorded, presuming the firmware is appropriate. Reducing the recording speed by half often produces better results simply because the drive is running below its maximum threshold: the recording laser diode runs at reduced power and the motor is also below its upper limit threshold. Firmware engineers generally design their drives to operate at a half rated speed. They can also include lower speeds, and sometimes they do. But these days the few firmware engineers left are forced to cut corners, and a 16X drive may only have suitable firmware settings for 16X, 8X, and 4X. Recording at 2.4X, 2X, or 1X may pose a problem (except in consumer video recorders whose designs always include 1X real-time settings.)

There is a further problem in the ability of dyes to properly record at speeds out of their design range. Faster reacting dyes are used for higher speeds, and at very slow speeds they may be "overburned" with marks that have larger, low-contrast edges that are associated with jitter and higher error rates. That is certainly the case with phthalocyanine dyes used in high-rated CD-Rs. They simply cannot be well recorded in 1x stereo machines with any good result. It is also true with the very limited ranges of rewritable discs whose narrow speed ranges limit them to 1-4X, 4-12X, 12X-24X, and so forth. It is the combination of fast reacting dyes designed for high speed recording and high speed drives with limited or no provisions for slow speed recording that create the problem of higher error rates for 16X rated media recorded at 2.4X in a modern high-speed drive.

DL media are a slightly different case. The pressure to lower prices has encouraged a number of DL producers to use a different method of manufacturing known as "inverse stack" or IS. Unlike the photo polymer method ("2P") that uses a temporary plastic stamper from a photo polymer that is hardened by UV light, then pulled off and discarded after creating the inner tracking groove for a double layer disc, the IS method creates the groove "upside down" on the layer applied to the disc substrate. This causes a problem for all but the latest DL drives that do not have firmware for recording this upside down layer. The developers knew that, so they have restricted IS DL discs to 8X speeds in the vain hope that retailers would keep both 4X and 8X DL discs on their shelves. That has not happened. So many people with older DL drives, or even with newer DL drives with limited firmware support, are finding problems with 8X DL discs. The prices have fallen dramatically because there is no 2P plastic to throw away and at least two manufacturing steps eliminated with IS production, and the yields and consistency are better. The problem for consumers as that these discs do not work well on older drives, and they do not work well at 2.4X because their design is focused (pun intended) on good response at 4X or 8X. For 8X DL media, 4X is the wisest speed, assuming that a drive can handle IS media in the first place.

The situation is a mess, and the fact that retailers limit their shelves to as few versions as possible (with limited technical knowledge of the products they are selling) makes things worse. This has been a problem for Verbatim who is forced to keeping higher prices because their 2P production process is more expensive, and to Taiyo Yuden who has been reluctant to get into DL production because of cost and because a late start means little to no firmware support and, consequently, a hit on their reputation when their newly introduced DL discs don't work.

In short, using the slowest speed is not the best recommendation for recording optical media. Using half the rated speed is more likely to produce a good recording as well as extend the life of one's drive.


----------------------------------------------------------------------------------------

A 2.4X burner will not have the firmware for recording an 8X disc. The original idea behind recorders was to have them record test signals on an isolated section of a disc to determine the proper power levels and pulse rates for that disc. Early burners did have that feature; but with the price wars forcing manufacturers to take shortcuts, fixed settings based on the recognition of a series of MID codes is all that's left.

A 2.4X burner may be unable to record an 8X disc, or may attempt to record it with poor results, or--in some lucky combinations--be able to record with acceptable results. The laser diode in a 2.4X burner will be capable of far less power output than today's faster burners, particularly the DL drives. The dyes used in high-speed discs are tuned for fast reaction by chemical modifications as well as thinner dispersions. Sometimes the power supplied by a laser diode at 2.4X might work well with an 8X disc (single-layer only, of course) or even a 16X disc. I have run hundreds of compatibility tests of high speed discs with all sorts of drives, however, and I don't remember a case in which an older drive with fixed settings delivered good results.


---------------------------------------------------------------------------------------


The recording speeds of DVD+R DL discs are: 2.4X, 4X, and 8X. 2P DL production can work at all three speeds, assuming that the drive firmware allows recording at 2.4X for an 8X DL drive. Not all 8X DL drives do allow that slowest speed because it is an extra setting that has to be designed and written into the firmware memory.

8X inverse stack DL discs, however, may not work well at 2.4X; and they are very unlikely to work on older 4X and 2.4X DL drives. Verbatim may still be using the 2P process for 8X DL production, and their higher costs/prices probably reflect that decision. Ricoh and Ritek have definitely moved to IS for 8X production, and successfully recording those less expensive 8X DL discs requires a more modern drive with firmware that allows recording on IS discs.

If your drive supports 2.4X recording on Verbatim 8X DL discs, then the advice is correct. If your drive only supports 4X recording on those discs, it would not be wise to force a slower speed because the original firmware does not support the slower speed. As for 8X IS DL discs, only drives from the last two or three years can support them; and 4X is probably the better speed.




---------------------------------------------------------------------------------------------



Verbatim from Singapore are DVD+R DL discs. Verbatim from Taiwan are CMC production. Verbatim from India are Moser Bayer. Maxell from Japan are Taiyo Yuden, the only Japanese manufacturer left. Maxell from Taiwan are Ritek. Memorex are usually CMC or Ritek. All of these brands are A-grade production. The reason Memorex are less expensive ("cheaper") than the others is due to market shares in the 30% range in North America, not Europe, that allows huge volume purchases. That is the case for standard DVD+/-R. As for DVD+R DL, they buy the IS production from Ritek that is, by the nature of the manufacturing method, far less expensive than the 2P manufacturing method that Verbatim uses for DVD+R DL discs.

The cheapest discs on the market are often brands that few people recognize. They tend to be B-grade stock that some factories dump. In those cases the cheap=low quality rule applies, but not in the case of recognized brand names.


--------------------------------------------------------------------------------------------------



CMC manufactures Verbatim discs using a Mitsubishi dye. It's true that Verbatim/Mitsubishi sets the specifications and provides the dye and the stamper, but the production is CMC production. CMC also produces TDK, Imation, Memorex, and HP for Imation TO IMATION SPECIFICATIONS. That means the lines and equipment and processes are all specified as well as the quality specifications of the finished goods provided by factory test results and correlating test results from incoming inspections. Not so big a difference after all, if honesty is really what you want.

The Philips book standards determine the grade level. Everyone still uses those standards as definitive. They all use the same test equipment to ascertain the results (with the exception of one company not mentioned). Compatibility is another issue. A "high amount of failures" is often due to incompatibility, and consumers who do not understand the complexity of the issues assume that A-grade means it works and B- or C-grade is something less reliable. But A-grade material from Ritek or CMC may fail on a drive simply because the drive is not compatible with the discs. Inverse stack 8X DL is a great case in point--probably more uniform production but greater incompatibility. That greater incompatibility leads many people to accuse IS material of inferiority when it is more likely that the product will be free of contaminants.

There are electrical standards that are defined and determined by book standards, specified by buyers who are willing to pay for the best product, and checked by both manufacturer and buyer with identical equipment (internally calibrated but, unfortunately, not correlated often enough); and there are cosmetic standards that are defined for all A-grade product, and examples are on all the walls of the manufacturing plants for operators to use for comparison. That would seem to me to be set grading standards and not a "meaningless term."

ENDO that is one of the strangest POSTS I've ever seen... what happened to it?? I think there's some good info but you get an A+ for weird!!1 hehehehe.

Originally Posted by greensman

ENDO that is one of the strangest POSTS I've ever seen... what happened to it?? I think there's some good info but you get an A+ for weird!!1 hehehehe.

gm, we are playing jeopardy, so the answer is.................

Originally Posted by greensman

ENDO that is one of the strangest POSTS I've ever seen... what happened to it?? I think there's some good info but you get an A+ for weird!!1 hehehehe.

I am going to agree with you on that one GM

C'mon guys, although they appear as random facts, they are indeed random facts that sometimes help to explain life and blank dvds