Re: [gentoo-user] new machine : DVD drive

[Pandu Poluan]

On Aug 20, 2012 7:47 PM, "Andrea Conti" <alyf@××××.net> wrote:
>

[snip]

> >
> > Yes, +RW, -RW, but don't know much more on this other than older DVD
writers
> > would only do one format not another and if you didn't pay attention to
the
> > specification/limitations of your hardware you could end up buying the
wrong
> > type of DVDs.  Someone more experienced on recording media could answer
this
> > better.
>
> Every modern recorder does both standards; depending on both the burner
> and the reader you might find that one standard works better than the
> other (i.e. has lower read error rates). Trial and error seems to be the
> only working approach...
>
> As for the standards, if you're just burning backups they're basically
> equivalent. The +RW standard is theoretically more flexible as media can
> be formatted in a "packet" mode which allows (almost) random r/w access,
> but in my experience software support and reliability have always been
> lousy, so forget about it.
>
> +RW media cannot be erased in the same way CD-RWs are erased, -- you can
> only overwrite it with new data. -RW behaves the same as CD-RWs in this
> regard.
>
> If you need rewritable DVD media with reliable random r/w access (but
> this doesn't seem to be your case), there is a third standard (DVD-RAM)
> which uses special disks with hardware sector marks. Drive support is
> not hard to find nowadays (the drive you cited actually supports it),
> but writing is slow, good media is expensive and the disks cannot be
> read in most "normal" dvd drives; I have no idea about the state of
> software support in Linux.
>

+RW *can* be erased, or else it won't be called RW :-)

That said, the difference is much deeper than differing metadata. Among
which :

* +RW uses Phase Modulation, -RW uses amplitude modulation. This gives +RW
much more robustness than -RW

* +RW blanks provide more info on the energy level required to burn, IIRC
up to 4 energy levels each tuned to a certain burning speed (e.g., 1x, 2x,
4x, and 8x). This *greatly* improves the success probability of burning.
-RW only provides energy level info for the maximum burning speed; if your
drive doesn't support that speed, it'll have to guess, and the results are
usually ungood

More history :

The CD Standard was originally developed by Philips, then adapted to the
data world requirements, including CD-R(W).  The DVD-R standard was
originally developed by Panasonic, but Philips had a spat with Panasonic
because in Phillips' view, the CD-R standard has shortcomings they
(Philips) want to fix; Panasonic was more interested in getting DVD-R out
of the door asap. This resulted in Philips -- together with someone else,
was it Sony? -- to independently released the DVD+R standard.

CMIIW

Rgds,