M-Disc is based on DVD+R but Verbatim Gold Archival Grade on DVD-R?

The DVD version of M-Disc is based on DVD+R, while Verbatim Archival Grade (Gold) is based on DVD-R.
Is there any reason for that difference?.

I also don’t know the real reason behind them
But a report in 2007 by French Archive suggests that Verbatim’s Archival Grade DVD-R actually has shorter lifespan than their normal consumer grade DVD-R.

DVD-R gold has a shorter lifespan despite of superior quality? How is that possible?

Lower reflectivity as the disk ages reflectivity becomes more important. Gold is good for ageing slower but doesn’t reflect as well.

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That’s why stronger disc drives and lower writing speeds are necessary, especially for archival.
When using a slim laptop drive to write to archivable storage, one should select the minimum speed.

There are two completely separate questions here.

For the differences between DVD-R/RW and DVD+R/RW, I suggest reading the excellent article CDFreaks/MyCE member Spath wrote 14 years ago. None of the technical differences between + or - should make any difference to the longevity of discs. One could hypothesise that the superior tracking of DVD+R/RW might be advantageous when trying to read a badly degraded disc (and maybe that influenced M-Disc’s choice), but I suspect with modern drives it would make little if any difference.

The significant differences between Verbatim Archival Grade and M-Disc DVDs have nothing to do with plusses or minuses, but is far more interesting.

The M-Disc DVDs are of a completely different construction to all other DVD±R (& CD-R) discs. Instead of an organic dye for the data layer and a separate metallic reflective layer, M-Disc discs use a single inorganic mineral layer. This has to be able to absorb enough energy from the laser during writing to undergo some sort of change so that data can be encoded onto it, but is also reflective enough not to need a separate reflective layer. Millenniata/M-Disc have always been very secretive about what this material is and how it behaves, and since the beginning most of their promotional material was very misleading (to the point of, it appears, occasionally being untruthful - for many years they claimed the data was “set in stone”). But it seems the material can best be described as a “glassy carbon”.

Unlike M-Disc, Verbatim’s Ultralife Archival Grade discs are not fundamentally different to convention DVD±R discs. They use a conventional AZO dye for the data layer and silver alloy for the reflective layer. What makes them different is that they have an additional gold layer, but this is not used as the reflective layer as was the case with early CD-R discs. Instead the gold layer is used as a chemically inert (and translucent) barrier to protect the silver layer from oxidation.



:disagree: :disagree: :disagree:

A slower writing speed does not necessarily equal better writing quality. And neither speed not writing quality have anything to do with the longevity of discs.

One can reasonably conclude that a slow writing speed is necessary for the M-Disc DVDs because the material used for the data layer requires greater heat (and thus energy from the laser) to flip from its default state to its low reflectivity state which simulates the pits of factory-pressed DVDs. The laser energy applied to a point on the disc is dependent on the laser power and the exposure time. So if an M-Disc requires more energy to write than a convention DVD, you would need to either develop a new, more powerful laser diode or just write them at a slower speed (thus increasing the exposure time).

Incidentally, there is no point in writing any optical discs at a higher than normal power. Doing so would not increase their ‘pit depth’ as many people suppose (recordable optical discs don’t have pits). What would happen is that the point on the disc being written to will overheat and (in the case of dye-based discs) a larger than intended area of dye will decompose. At best you would see elevated jitter & poor beta (pit/land symmetry) and maybe tracking problems. In the worst case you would get data errors.

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Thank you for your post, Ibex.
:black_small_square:I think, that somebody could build an open sourced hardware version of M-Disc. Patents? Patents cripple progress and developement in mankind.
:black_small_square:In my opinion, both -R and +R and RW should exist.

Very interesting!
I was just about to ask about pit depth.

I back up a new AudioCD using cdparanoia to a PC.
For portable transport, I add it by MP3 (I know that Xiph is superior) to a low-quality CD-R/CD-RW (from eBay) by using packet writing. It is no problem if they degrade, because they are not necessarily needed to last long. Additionally, despite I hate disc rot (who doesn’t?), the science of it is interesting and losing the low quality discs is not tragic. Each of the CD-R’s only costs around 15 cents. CD-RW (×8-×12 HighSpeed) costs 30 ct at lowest.

Using BE14NU40 at ×24 CAV, even these low quality discs have no C2 errors. C1 errors: less than thirty per disc in total. Let’s see, how much from the low quality trash CD-Rs is left five years later.

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