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DVD+R DL capacity question

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DVD+R DL capacity question

Postby gomtuu on Mon Feb 21, 2005 6:42 pm

Hello,

I'm having difficulty finding this information, so hopefully someone here can help me out:

1. I've read that a DVD+R DL's 8.5GB capacity is "fully equal" to commerical DVD-Video DL discs. Is this true?

2. When people say "8.5 GB," do they mean 8.5 billion bytes, or 8.5 * 2^30 bytes? Is it even exactly 8.5, or is that a rounded figure?

3. Exactly how much user data does each layer of a +R DL disc store? (Is the capacity split evenly between them, or can one layer hold more than the other?)

4. I've read that there are complications with custom layer breaks on +R DL discs that don't necessarily exist for DVD-Video DL discs. Namely, the layer break on a +R DL has to be at the halfway point of the data. Is this true? If so, does this cause problems when trying to copy DVD-Video DL discs?

5. Are there any other caveats related to +R DLs that I haven't even considered?

6. Are the answers to these questions different at all for -R DL discs?

Thank you,
-Don
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Postby VideoRoy on Mon Feb 21, 2005 7:00 pm

Others here may be able to answer your questions straight away but I thought I would point you to a great FAQ I have referenced in the past.

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Postby VideoRoy on Mon Feb 21, 2005 7:09 pm

I almost forgot this one as well:

DVD Plus RW

I think there is a minus R .org as well but it escapes me right now.
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Postby dodecahedron on Mon Feb 21, 2005 8:51 pm

1. no a commercial (pressed) dual-layer DVD is closer to 9GB

2. GB = 1,000,000,000 alas
it's a rounded figure
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Postby dolphinius_rex on Mon Feb 21, 2005 11:16 pm

dodecahedron wrote:1. no a commercial (pressed) dual-layer DVD is closer to 9GB


According to DVD Demystified that is incorrect:
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And from my own experience working with replicated dual layer DVDs, I would have to agree with the FAQ.
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Postby dodecahedron on Tue Feb 22, 2005 2:50 am

dolphinius_rex wrote:
dodecahedron wrote:1. no a commercial (pressed) dual-layer DVD is closer to 9GB


According to DVD Demystified that is incorrect:
clicky

And from my own experience working with replicated dual layer DVDs, I would have to agree with the FAQ.

i stand corrected. :)
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Postby alexnoe on Tue Feb 22, 2005 7:21 am

If you have ever really seen a pressed disc with more than 4173824 sectors (i.e. more than about 8,55 *10^3 bytes), tell me. All I can say is that DVD Maestro has a limit below that for doublelayer mastering, and dvd maestro definitely knows nothing about double layer recordables
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Re: DVD+R DL capacity question

Postby Boba_Fett on Tue Feb 22, 2005 12:42 pm

gomtuu wrote:2. When people say "8.5 GB," do they mean 8.5 billion bytes, or 8.5 * 2^30 bytes? Is it even exactly 8.5, or is that a rounded figure?


They litterally mean approx. 8.5 billion bytes. Unfortunately, media manufacturers (like HDD makers) think of 1000MB as one GB instead of the correct 1074MB (approx.), so when they sell us a 4.7GB DVD-+R, Windows sees that in binary form as 4.371GB (7% less capacity). So, technically, a DVD+-R DL (or pressed Dual Layer) with a advertised 8.5GB capacity would only hold a maximum of 7.905GB. Ever wonder why your 100GB HDD only shows up as 93GB in Windows? That's why...
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Postby alexnoe on Tue Feb 22, 2005 12:49 pm

7,96 GB
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Re: DVD+R DL capacity question

Postby jsl on Tue Feb 22, 2005 2:29 pm

Boba_Fett wrote:Unfortunately, media manufacturers (like HDD makers) think of 1000MB as one GB instead of the correct 1024MB (approx.)

Nah, media manufacturers are correct. A prefix should have the same meaning regardless of application, hence kilo = 1000 and so on. So start using the binary prefixes instead of misusing the SI prefixes ;) http://physics.nist.gov/cuu/Units/binary.html
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Postby Boba_Fett on Tue Feb 22, 2005 7:56 pm

Bah, fixed my definition of one real gigabyte (what some people refer to as a gibibyte now)...

Anyway, the single reason media and HDD manufactuers use this method is to make their product seem bigger than it really is. Selling 93GB drives and offering them as 100GB seemed to be a pretty good idea. Not :cry:
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