Miark wrote:

On Tue, 26 Oct 2004 10:18:17 +0100, John wrote:



ls -l <iso image file>

Divide the size of the ISO image file by 2048 to get the
number of sectors, and record that sum (=n, hereafter)



If it comes out to a decimal, do I round up?

It doesn't.
The sectors in question are the number of sectors on the disc.
So whatever amount of bytes on a disc it will always come out
a whole sector number. The spiral of the lazer track begins on the
inner circumference and winds itself out to the outer. That
spiral is devided up into so many sectors.
So byte 1 is in sector 1 , byte 2049 is in sector 2, etc
At least that is how I understand it. I don't pretend
to be an expert.

in terminal,
dd if=/dev/scd0 bs=2048 count=n | md5sum -
(note the " - " on the end, don't leave it off.



It still comes out different. Although I think I forgot to double-check the sectors written by cdrecord.


Then I suspect you have a failed disc write.
If you did the above right and it still gives
a wrong md5sum something is wrong
somewhere.

At this stage I would begin to suspect media next.
Maybe the choice of media/burner match is not
a good one. It does happen. I have to say that
I have never yet had such a problem, but I know
others have. I cannot say whether that is more a
problem of the user or the media. I tend to
believe the user is more at fault than the media,
but that could be my wrong assumption on my
part and until I experience the same it is very
difficult to arrive at a sound conclusion.

The dye that is used on some media is not
necessarily the best type of dye/media for your
burner. The frequency of the lazers may vary,
or the intensity of the lazer may not be
adequate for safe reliable burns, who
knows, I don't. But they are variables and
could be a cause of concern. The situation
is not made better by the device manufacturers
who in my experience don't want to suggest any
particular make/specification for their burners.

Basically it's left to the user to resolve.

So right now I'd double check what you have
just done above, and if you are satisfied it
is still not coming out right I think I would
beg borrow or acquire some different makes
of media to see if it makes any difference.

John


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