On Fri, 2004-09-10 at 13:02, Levi Bard wrote:
> And, btw, according to http://fy.chalmers.se/~appro/linux/DVD+RW/ ,
> it's recording. As in writing a TAO session.
Disc-At-Once (DAO) is how DVD-Rs should be written for absolute
compatibility with consumer players and even the oldest DVD-ROM drives.
It is a byte-by-byte (character device) "record."
DVD+RW and DVD+R don't seem to support DAO, which is where the
compatibility problem occurs. Because of how Sony/Philips approached
DVD+RW in the first place, it has that inherit limitation. Other
advantages aside, it will _never_ be as compatible as DVD-R.
Now he gets confused on DVD-RW and DAO. He lists the fact that DVD-RW
can also support DAO as a "negative," because it doesn't allow direct
overwrite. That's not a limitation with DVD-RW, that's a limitation
with DAO. In a nutshell, you can't "re-write" if you're not writing 2KB
blocks, but every 1 byte character. Simple logic.
TAO is what "packet writing" uses. DVD-RW _can_ do TAO as well, just
like DVD+RW.
As far as "buffer underrun" in DAO, he's talking about the "packet
write" approach. There _is_ support for "turning off the laser" in DOA,
but you _will_ take a massive performance hit as a result.
Of course doing "packet writing" would be 100x better than "recording"
when it comes to "buffer underruns." But then we're back to the DAO
versus anything else.
So far, I've been vastly unimpressed with the "fudging of facts" I've
seen on the DVD+RW-Tools page in years prior. Although they've cleaned
up some of the blantantly false assumptions. Sony/Philips had an
innovative idea for DVD.
Unfortunately, it failed. Everything's been a retrofit since. Some
people stand behind DVD+RW, but a quick review of the history, and it's
one full of false advertising -- even if the latest generations
_finally_ deliver on most of original promise (sans DAO recording).
DVD-R and DVD-RW are designed for maximum compatibility, but that is
_only_ guaranteed with DAO with CLV media/modes. Because most of
DVD-RW's incompatibility is due to the MO design and media frequency,
DVD+RW isn't really any less compatible than DVD-RW (around 70% and
getting better as newer drives dominate the consumer front).
But DVD+R is far less compatible than DVD-R because it doesn't offer
DOA, CLV and, most importantly, it's not a WORM media.
> And it has some Pioneer and Panasonic drives listed in the HCL, but it
> doesn't specifically make an issue of the two types of firmware.
Sounds like they have updated it with DVD Consortium drive support.
I'll check it out.
--
Linux Enthusiasts call me anti-Linux.
Windows Enthusisats call me anti-Microsoft.
They both must be correct because I have over a
decade of experience with both in mission critical
environments, resulting in a bigotry dedicated to
mitigating risk and focusing on technologies ...
not products or vendors
--------------------------------------------------
Bryan J. Smith, E.I. b.j.smith at ieee.org
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