Re: Which DVD Media Do I Need?
- From: Jim Howes <jimhowes@xxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 31 Dec 2007 22:13:57 +0000
Davy wrote:
I am purchasing a Lite-On LH-20A1H which can handle
20x 8x 8x / 20x 8x 6x / 12x /16x + 48x 32x 48x, Double Layer DVD+/-R9,
DVD-RAM
I need to buy some DVD blanks to go with it. What of the three options
should I choose?
You may find that your particular drive lists particular media
manufacturers that they recommend. However, here's my tuppence worth..
Obviously -R and +R discs are write-once. Given the cheapness of the
two, this may not be a problem, given that bulk discs will set you back
of the order of 15p/disc.
There are a lot of differences between how -R and +R discs are actually
written, but I'll let you gather that information yourself as it is just
plain confusing.
Your choice of whether to use + or - is far more likely to be influenced
by external factors. I have a Pioneer HD/DVD video recorder, and that
only eats DVD-R and DVD-RW, so that's my main reason for buying bulk
DVD-R media (with a ritek G.05 dye from svp.co.uk for what it's worth).
A friend has a camcorder that only eats DVD+R.
When it comes to rewritables, there a few more differences. DVD+RW
already has a pregroove written on it with addressing information in it
that the drive head uses to work out where it is on the disc (ADIP or
ADdress In Pregroove). DVD-RW lacks this, but uses a differnt
technique. (Pre-pits, More information in link below) Because most
drives calibrate themselves by moving the head out a short distance and
reading the sector information from where they end up, it is necessary,
when writing DVD-RW, to write at least 1Gb (typically) to create a disc
that will have meaningful information for another drive to calibrate
itself to that disk ('de-icing'). Hence DVD-RW will require longer to
write a small amount of information to on the first pass. Most software
will do this in the lead-out phase or pad a session to 1Gb to achieve this.
DVD+RW on the other hand requires formatting to write basic DVD volume
information to the disk. This formatting doesn't write much (i.e. it
does not write to every sector), but is required prior to the first use
of the disk. Most software handles that automatically, such you'll not
even notice it happening.
The '+' formats also allow you to change the 'book type' of the media to
fool older equipment that doesn't know how to recognise +R/+RW into
trating the media as a pressed DVD-ROM volume.
DVD-RAM is another kettle of fish. It does not require formatting as
per DVD+RW, nor does it need de-icing as per DVD-RW. One thing it DOES
have which makes it far superior for data interchange than the others is
integrated bad-block management. (Ok, so DVD+RW has this in the spec,
but it is rarely actually implemented) The big downside is speed; 3X
is about the maximum, although faster DVD-RAM is in development. DVD-RW
can be formatted with any filesystem you happen to like to use (such as
FAT32, linux ext2) or just written in UDF/ISO as a DVD+/-R(W). In
theory DVD+RW (and a fully-erased DVD-RW) can also hold arbitary
filesystems, but the lack of bad-block management causes those
filesystems to fall apart rather quickly.
Finally, if you are a movie studio and you want to create encrypted DVDs
with CPPM and CSS protection on, you'll need DVD-RA (DVD-R for Authoring
2.0) discs, and a writer that supports writing CSS keys and CPPM album
identifiers to to the control data zone on such media. Your shop-bought
device doesn't do that, period. (And if it did, the DVD forum would be
doing something about it)
If you're now confused, I'm not surprised. So I'll summarise...
I use DVD-R mainly because that is what my video recorder eats. If it
eat DVD+R, I'd probably use that. I don't use many -RW or +RW discs,
because neither seem to last long. For important stuff and backups I
write to DVD-RAM discs, because my backup scripts read the bad-block
information from the disk before and after writing to determine the
state of wear of the disk. (This is no substitute for verifying the
data by reading it back).
If I was going to use -RW or +RW, I'd probably go for +RW for pretty
much the same reason as detailed here
http://www.cdfreaks.com/reviews/Why-DVDRW-is-superior-to-DVD-RW
Regards,
Jim
.
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- Which DVD Media Do I Need?
- From: Davy
- Which DVD Media Do I Need?
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