How to determise the physical location of a file on a CD ?

I have to build an ISO with only two specs:
- I have to know where is a given file, I mean, I have to know how far
from the center of the CD is a particular file
- the file has to be alone in that zone.

I can choose what ever I want to do that: ISO, Joliet, or what ever.

Since I expect a CD to have interlaced sectors like a HDD, I think
that the easiest way is to declare two white 50M files, one before and
one after, and build the raw image using the UNIX tool mkisofs.

Then remain two questions :
- how to know where will be located the given file (on which circle it
will be burnt - how far from the center will it be )
- how to make sure no file will overlap that zone (how to make sure
only the two white files will be wixed in the same circles than the
given file)

Thanks for help.

(Doublehp) wrote in message . com...
I have to build an ISO with only two specs:
- I have to know where is a given file, I mean, I have to know how far
from the center of the CD is a particular file
- the file has to be alone in that zone.

I can choose what ever I want to do that: ISO, Joliet, or what ever.

Since I expect a CD to have interlaced sectors like a HDD, I think
that the easiest way is to declare two white 50M files, one before and
one after, and build the raw image using the UNIX tool mkisofs.

Then remain two questions :
- how to know where will be located the given file (on which circle it
will be burnt - how far from the center will it be )
- how to make sure no file will overlap that zone (how to make sure
only the two white files will be wixed in the same circles than the
given file)

Thanks for help.

You could just use a simple ratio to do the job. For example, if you
want the file half-way out from the middle, then you figure out the
ratio of the area of a circle to the area of a circle with half that
diameter. Then you will know how much "white file" to put on each
side of your real file, and it should go in the correct place.

Aaron

Doublehp wrote:

I have to build an ISO with only two specs:
- I have to know where is a given file, I mean, I have to know how far
from the center of the CD is a particular file
- the file has to be alone in that zone.

I can choose what ever I want to do that: ISO, Joliet, or what ever.

Since I expect a CD to have interlaced sectors like a HDD, I think
that the easiest way is to declare two white 50M files, one before and
one after, and build the raw image using the UNIX tool mkisofs.

Then remain two questions :
- how to know where will be located the given file (on which circle it
will be burnt - how far from the center will it be )
- how to make sure no file will overlap that zone (how to make sure
only the two white files will be wixed in the same circles than the
given file)

Thanks for help.

I'm assuming by 'circle' you mean 'track' and 'sector' some fraction
of a track, a la HDD. CD's don't work like HDD's. There is one
spiral track beginning near the spindle and ending near the outer
perimeter of the disk. Do some more reading.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

(Aaron) wrote in message . com...
(Doublehp) wrote in message . com...
I have to build an ISO with only two specs:
- I have to know where is a given file, I mean, I have to know how far
from the center of the CD is a particular file
- the file has to be alone in that zone.

I can choose what ever I want to do that: ISO, Joliet, or what ever.

Since I expect a CD to have interlaced sectors like a HDD, I think
that the easiest way is to declare two white 50M files, one before and
one after, and build the raw image using the UNIX tool mkisofs.

Then remain two questions :
- how to know where will be located the given file (on which circle it
will be burnt - how far from the center will it be )
- how to make sure no file will overlap that zone (how to make sure
only the two white files will be wixed in the same circles than the
given file)

Thanks for help.

You could just use a simple ratio to do the job. For example, if you
want the file half-way out from the middle, then you figure out the
ratio of the area of a circle to the area of a circle with half that
diameter. Then you will know how much "white file" to put on each
side of your real file, and it should go in the correct place.

Aaron

Whoa, looks like you (doublehp) accidently cross posted. Here is your
quote:

that does not look possible because the spread of a file is not linear:
the middle of the disk do not contain the middle of the ISO ... I know
that it is a very complex equation ... the middle of the ISO is near the
outside border ...

doublehp

Well, I don't think that it is so complex. It should be fairly
similar (in fact, derived from) the formula for the area of a circle:
(pi)(r)^2=(area)

So, let's do an example: You want a track burned 1/3 out from the
middle (measuring from where the data starts). Use a ruler, and find
out how far from center of CD that is. Find the area using that
radius, and then subtract the area of the middle of the CD (the
"hole"). Thus, after subtracting the two, you have the "area" of data
that you will need before your track. We will call this area1.

Next you need to figure out the area of the data you need after your
track. This is similar to the above. First, find out the total area
of the disk, and then subtract from that the area of the "hole". Also
subtract the area of the data before your track, and then you will
have the second of your two numbers. We will call this area2.

Now we want those in ratio. So put it like this area1:area2
For 1/3, I guessing maybe...well, I don't know, and I don't have the
correct tools here with me at school to try it out, so you're on your
own.

Anyway, with your ratio, just make two of your "white files" with
proper lengths so as to fill the CD (that's important--CD must be
filled for track to be in proper location), keeping in mind that they
have to be in ratio also. That should about do it.

Hope it's understandable,

Aaron

Aaron writes:

You could just use a simple ratio to do the job. For example, if you
want the file half-way out from the middle, then you figure out the
ratio of the area of a circle to the area of a circle with half that
diameter. Then you will know how much "white file" to put on each
side of your real file, and it should go in the correct place.

Aaron

Whoa, looks like you (doublehp) accidently cross posted. Here is your
quote:

that does not look possible because the spread of a file is not linear:
the middle of the disk do not contain the middle of the ISO ... I know
that it is a very complex equation ... the middle of the ISO is near the
outside border ...

doublehp

Well, I don't think that it is so complex. It should be fairly
similar (in fact, derived from) the formula for the area of a circle:
(pi)(r)^2=(area)

So, let's do an example: You want a track burned 1/3 out from the
middle (measuring from where the data starts). Use a ruler, and find
out how far from center of CD that is. Find the area using that
radius, and then subtract the area of the middle of the CD (the
"hole"). Thus, after subtracting the two, you have the "area" of data
that you will need before your track. We will call this area1.

Next you need to figure out the area of the data you need after your
track. This is similar to the above. First, find out the total area
of the disk, and then subtract from that the area of the "hole". Also
subtract the area of the data before your track, and then you will
have the second of your two numbers. We will call this area2.

Now we want those in ratio. So put it like this area1:area2
For 1/3, I guessing maybe...well, I don't know, and I don't have the
correct tools here with me at school to try it out, so you're on your
own.

Anyway, with your ratio, just make two of your "white files" with
proper lengths so as to fill the CD (that's important--CD must be
filled for track to be in proper location), keeping in mind that they
have to be in ratio also. That should about do it.

I think you are assuming bits per square inch is a constant. AFAIK CDs
maintain a constant head velocity which means lineal bits/inch is a
variable; a function of where the square inch is on the physical CD.

kevin wrote:
) I think you are assuming bits per square inch is a constant. AFAIK CDs
) maintain a constant head velocity which means lineal bits/inch is a
) variable; a function of where the square inch is on the physical CD.

CDs maintain a constant *linear* velocity which means that the number of
bits/inch along the line *is* constant, and therefore the number of
bits/sqare inch is also constant.

You may be thinking of constant *angular* velocity.


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT