Re: [Dvdrtools-users] DVD+R/+RW support

[Bryan J . Smith]

FYI, when I say CLV MO I mean "Net CLV."
MO, like magnetic, is always "gross CAV."
That means the disc spindle is constant.

CLV in traditional ROM or WORM means we "slow down" the spindle so the 
linear velocity is the same.
Because in ROM and WORM, the single, long groove has the same spacing.
We can spin at a CAV to pick up more bits on the outer tracks.
From the standpoint of recording WORM, CLV and CAV result in no physical 
difference at all.
It's very easy to time this because ROM/WORM not only have "data pits", 
but "timing pits" in between them.

MO doesn't.

So for MO, everything changes.
Because MO is always "gross CAV," we can choose to implement it as "net 
CLV" or "CAV" - "Net CLV" is how we always did it before Sony/Philips' 
10x CD-RW.
PD-CD, DVD-RAM, CD-RW and DVD-RW do "net CLV."
They space data out so the outter tracks have the same total data as the 
linear tracks.
As such, it is easier for consumer players to read MO and time the data 
areas, it merely spins at a CAV, but reads the same CLV whether it is on 
an inner track or outter.

In PD-CD and DVD-RAM, you can see the physical "tabs" in the media.
It also means that parts of the CLV media is *not* for data.

For full CAV MO, every piece of the disc is used.
This is how non-standard CD-RW CAV works, as well as DVD+RW and DVD+R.
It's also how Sony/Philips got 3GB out of a MO disc when Matsushita got 
2.6GB (like traditional Net-CLV MO drives).
Unfortunately, timing is now difficult because there are no "timing 
pits" in MO (unlike ROM/WORM), and we can't merely use a consistent 
timing like "Net CLV" MO for both inner and outer tracks.

CAV MO media in a drive that doesn't know how to use it is going to 
cause issues.
Because the drive expects the data to be "spread out" on the latter 
tracks, so not reading the "packed" data (and likely mis-aligning in the 
process).
I have had numerous players no longer read DVD-ROM or DVD-R disks after 
attempting to read just 1 DVD+RW/+R disc until it's heads were run 
through a re-alignment program.






Bryan J. Smith wrote:
> An additional issue in DVD+R/+RW v. DVD-RW/RAM is CAV v. CLV,
> respectively.
> CLV MO always has the same, relative layout.
> CAV MO requires "gap fill-in" that is not consistent.
> It's much, much easier to accomodate MO CLV than MO CAV.
> Which is why official CD-RW MO standards *never* introduced CAV, they
> were always CLV.
> Even the 8x and higher Pioneer standards were CLV MO.
> Sony/Philips introduced 10x and higher standards using CAV MO, which has
> been attributed to shortening of drive lifespans and reduced
> compatibility.
> I used to refer to it as CD+RW.
> At least there is no more confusion in the DVD arena.
> But the issues with DVD+RW remain for non-DVD+RW consortium drives.
> MO is already a support issue for players, but CAV MO is even worse.
> Hence the problem with DVD+RW compatibility on even Sony/Philips
> consumer drives.
> Again, I'll show this in the fact I'm writing.
--
Bryan J. Smith   mailto:address@hidden
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