Re: [Dvdrtools-users] media reliability

[Bryan J. Smith]

Quoting Scott Prive <address@hidden>:
> Really? How are DVD-RAM more reliable than DVD-RW/+RW? Is there some
> additional error checking in the disc format? I'm assuming it's not a
> media or "manufacturing" issue you base this on.

It's a combination.

First off, understand _why_ DVD-RAM was created first -- as well as Panasonic
"Phase-Dual" CD (PD-CD) before that.

There were endless proprietary archiving standards in the late '80s and early
'90s.  Some were basic Magneto-Optical media approaches (which both CD-RW as
well as DVD-RW and +RW do today), while others added extensive CRC checking and
autocorrection algorithms.

IMPORTANT POINT:  Magneto-Optical media, used in CD-RW, DVD-RW and DVD+RW (and
DVD+R too???), is _far_less_reliable_ than typical Dyed, Write-Once media used
for CD-R and DVD-R.  The typical media lifespan before errors on the former is
only 3 years, compared to about 30 in the latter.  I know, I've got 3 year-old
CD-RW backups that are now experiencing single bit failures, but DVD-RAM discs
that read perfectly.



DVD-RAM was first introduced in the mid-90s after their successful PD-CD series.
  Both offer extensive checksum checking and recovery, at the expense of the
following:

 - SLOW!  The added checking requires many re-reads of the laser, decreasing
performance 40%!  A 1x DVD-RAM (1.35MBps) is really only capable of 0.6x speeds
(0.8MBps).

 - General media incompatibility with CD and DVD players.  The focus is not on
consumer compatibility, hence the result.  Only select DVD-RAM partner DVD-ROM
drives will read disks, but really nothing else.  But DVD-RAM is a hugely
popular optical archiving standard, so the drives still sell.

 - [No longer true:]  Increased cost, although far cheaper than previous,
proprietary optical formats.  I bought a DVD-RAM drive for $500 in 1998, and
they were sub-$1,000 before that.  DVD-RAM drives have been "commodity" since
2000, costing well under $300, now even under $200.  I see DVD-RW and +RW drives
have dropped in price to under $400 and even $300 too.

Furthermore, the technology at the time was only 2.6GB/side, which was
commonplace in the optical archiving world (as were the previous 650MB, 1.3GB
sizes), so it fit nicely.  Like most optical drives, and PD-CD before it,
DVD-RAM was offered in a double-sided, cartridged media, which further improves
lifespan) -- although single-side media _do_ exist (and _are_ readable in many
DVD-RAM partner's drives like Panasonic, Toshiba and a handful of others, but
not generally).

But they opened it up as a standard, which took the archiving world by storm. 
The DVD consortium adopted it as its "rewrite" standard, to complement its
DVD-R(A[uthoring]) and, planned, DVD-R(G[eneral]) "write once" standard.  The
DVD consortium was also toying with creating a more "consumer" rewrite standard
(which would become DVD-RW), once the technology became feasible for 4.7GB/side
capacities.

As far as Linux, the "savings" of the original PD-CD over proprietary optical
led to drivers being written back well before DVD-RAM.  DVD-RAM uses the same
firmware as PD-CD, so DVD-RAM worked "off-the-bat" (with a small vendor ID
patch) in Linux.  I know, I had a drive in 1998 that did.  ;-P

2nd generation DVD-RAM hit in 2000, and increased the capacity to 4.7GB/side. 
Today DVD-RAM is now 3rd generation, which includes the ability to "record"
DVD-R(G) as well.  Unfortunately, dvdrtools doesn't support that yet, which
keeps me from upgrading to a 3rd generation DVD-RAM drive just yet.  ;-P

> You can be more direct that that: DVD+RW customers were lied to, and
> this was the basis of a class-action lawsuit against HP (or did they
> settle before class action status?) 

I warned everyone about those 1st generation DVD+RW drives.  Sony/Philips has
lied about their "non-standard" implementation over and over, promising again
and again.  I watched their original 3GB DVD-R+W (or whatever they called it)
end up being "less-than-compatible" but they market otherwise.  So when they
said a "DVD+R" was "planned," I said, "not with their current drive for sure!"

The latest "broken promise" (which I haven't confirmed) is DVD+R being
"less-than-as-compatible" as DVD-R(G).  While everyone debates whether or not
DVD-RW or DVD+RW "rewrite" standards are more compatible -- most people peg them
at ~70%, DVD-R(G) is nearly 100% compatible because the DVD-R format has been
around for so long (as long as DVD-RAM) -- using a very _different_ approach
than DVD-RW.  But DVD+R still uses the DVD+RW technology, which results in
"less-than-100%-compatible" drives -- basically only DVD+RW partners drives,
just like DVD+RW.

> I'd say DVD+RW playback support is even lower. I based my recorder
> purchase on this very issue (almost nothing else). Hanging out in the
> "DVD Recording" forums of Digital Digest, VCD Info, etc. I concluded
> there were many "DVD+R experts" who didn't even have a burner yet, and
> were just buying into the information at dvdplusrw.org.

Correct.  DVD+R is again, not looking good there.

And their line about not supporting DVD-R(G) because of "technical issues" is BS
IMHO.  If Panasonic can get their 3rd generation DVD-RAM drives to do DVD-R(G),
then Sony/Philips could have too.

It's all about making extra money.  Sony/Philips released their proprietary 3GB
DVD-R+W drive in Japan in 2000 because they wanted to ransack their world with
their own standard.  Fortunately, 2nd gen DVD-RAM appeared with 4.7GB/side about
the same time, and Pioneer was about to release their new DVD-RW "consumer"
drive with 4.7GB disks.

Sony/Philips just delivers way too late.

> You can get a fair idea of compatability by looking up your player at:
> http://www.vcdhelp.com/dvdplayers
> Unfortunately there is no summary of -R/+R compatability % in this
> database.
> Note that if there are a low number of reports for a DVD Player model,
> the data is inconclusive: "failures" could simply be with one brand of
> media, as was the case with my older Pioneer drive. So an "unsupported"
> model may still work (if you are lucky).

You can't go wrong with DVD-R(A) or DVD-R(G) when it comes to compatibility, and
DVD+R has yet to show it matches for "write-once/record" media.

When it comes to "rewrite":

  DVD-RAM is for long-term archiving, and is the "optical archiving standard"
that non-consumers were asking for a dozen years ago

  DVD-RW is for consumers who want a DVD Consortium standard

  DVD+RW is for consumers who favor the PC OEM's standard (who Sony/Philips has
marketed to)

-- 
Bryan J. Smith, E.I.            Contact Info:  http://thebs.org
A+/i-Net+/Linux+/Network+/Server+ CCNA CIWA CNA SCSA/SCWSE/SCNA
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