Arfa Daily wrote in message
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"EDM" wrote in message
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"Franc Zabkar" wrote in message
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On Mon, 21 Aug 2006 09:50:21 +0200, "Bart Bervoets"
put finger to keyboard and composed:
Don't know about that but I always burn at a lower than maximum
speed
because apparently the "image" is burnt deeper and supposed to be
less
liable to long term temp/humidity/corrosion corruption of the stored
disc
data.
Agree there, i have tested this on some sample dvdr's and after
burning
the
same image
at 1x, 2x, 4x and 8x i could already see the imprint on the disc
getting
much lighter.
That's a worry. I would have expected that the firmware would have
adjusted the laser power for a consistent burn at all speeds.
Apparently not.
Cheaper models don't have an adjustable laser, and for the cost
of ones that do (BenQ, NEC etc, around 35-40 clams) there's
no excuse for using one that doesn't.
Part of the problem with playing back home recorded disc media, is that
the
technology to record the data, is different. A number of times, pits and
lands have been mentioned in this thread, but these only exist for factory
pressed media. Home burnt media rely on changing the physical state of a
dye
layer in the disc, which alters its reflectivity. This is not as good as
having silvered pits and lands. The reflectivity of home burn discs is not
as good as pressed discs in the first place, which degrades the relative
signal to noise ratio of the recovered data. Add to this, the fact that
you
are firing either a near infra red or visible red laser at a disc that may
have a blue or green or purple dye layer, and you are soon in trouble at
getting reliable reading, if the record process is anything less than as
perfect as it can be.
For this reason, I would suggest that there will be a particular brand /
colour of disc that best suits the particular drive or player that the
disc
is to be played back in, and a maximum speed that that results in a high
enough signal to noise ratio for that disc / player combination, to ensure
reliable long-term readability.
To pursue the original question, if a range of discs recorded at different
speeds on a drive, exhibit a range of colour densities over the recorded
section, then this would indicate that the drive does not have the
capability to control the laser write power, and there should therefore be
no longevity improvement issue for the laser life, by writing at lower
speeds. If a range of discs exhibit a broadly similar colour density for a
range of writing speeds, then this would indicate that the drive does have
speed adaptive power control, in which case, the laser life would almost
certainly be increased by burning at lower speeds.
Arfa
So would a good policy be the following for any recordable media, ie
audio,video and data.
For a new media brand of use
Burn the same data at the minimum , maximum and 1 or 2 intermediate speeds
on 3 or 4 discs, label them specificaly for their ?x speeds for later
checking on environmental degradation/ data corruption.
If there is an observable gradation in the appearance of the 3 or 4 discs
then use a lower speed setting for recording on all the rest of the
batch/make. ?
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/