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Dual layer DVD capacity for video authoring?


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#1 of 10 Keith Paynter

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Posted December 29 2005 - 02:09 PM

This should be easy for someone...

Single layer DVD-R/DVD+R capacity for video projects use a maximum of 4.38GB out of 4.7, but what is the maximum capacity for video on 8.5GB dual layer discs, and is the capacity even on each layer?
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#2 of 10 mattCR

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Posted December 29 2005 - 04:40 PM

Having used DL discs, it seems as though 8.5G is the usable amount, as I've burned a Linux ISO Image (Mandrake DVD) that was 8.39Gb with no problems.

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#3 of 10 Ken Chan

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Posted December 30 2005 - 11:37 AM

Quote:
maximum of 4.38GB out of 4.7
There's a difference between billions of bytes (10^9) and gigabytes (2^30). A single-layer DVD holds 4.70BB, which is 4.38GB. Dual-layer is 8.55BB, or 7.96GB. Of course disc manufacturers use the units which give them bigger numbers, the billions of bytes.

With DVD-Video, that's almost all usable space. (Other formats set aside quite a bit for error correction or logical formatting.) So unless I read you wrong, there is no "out of" -- 4.38 "is" 4.7.

With dual-layer, each layer has the same capacity (which is less than a single-layer because each layer is physically more difficult to read), but the first layer recorded has to use at least as much as the second layer, because (in the most common case) the laser reverses direction when reading the second layer. Otherwise, it would "go off the edge".

#4 of 10 Patrick Sun

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Posted December 30 2005 - 11:51 AM

Just to confuse things, DVD-RAM now offers 9.4GB capability for their Dual-Layer DVD-RAM blank media. I bought a DVD burner drive for my Dad over the holidays and it claimed to be a multi- threat when it came to burning different DVD blank media classes (DVD+/- R, DVD+/- RW, DVD-RAM, and Dual layer types). But not many players can handle DVD-RAM, so that's probably a gee-whiz stat.
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#5 of 10 Keith Paynter

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Posted December 30 2005 - 01:55 PM

Quote:
So unless I read you wrong, there is no "out of" -- 4.38 "is" 4.7

Thanks Ken - I'm referring to useable space, and since I don't quite know the math to compare BB to GB, the numbers you've supplied are very helpful.

I'm trying to optimize my ensemble long-form videos for use on DL discs within the bitrate specifications (<10MBps, although I rarely like to higher than 7.5MBps, since some slower PC's/video cards tend to get choppy with excessively high bitrates).
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#6 of 10 Christ Reynolds

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Posted December 30 2005 - 10:26 PM

Quote:
I don't quite know the math to compare BB to GB
BB refers to a billion bytes, which is what hard drive and dvd capacities are sometimes measured in (on the box) to artificially inflate the size of a storage medium. a billion bytes is 1,000,000,000 bytes, but a gigabyte, an accurate measure of storage, is 1,073,741,824 bytes. a single layer dvd will hold 4.37 GB, or 4.7 billion bytes. just look at the GB number, the billion bytes number is just a marketing scam of sorts.

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#7 of 10 ChristopherDAC

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Posted December 31 2005 - 05:44 AM

It's hardly a scam, just a confusing use of a different system of measurement. Computer people like to use binary notation, and it happens that the tenth power of two is 1024; this they call a thousand as an approximation, and then proceed to use the standard powers-of-ten notation [kilo, mega, giga, tera...], but their numbers are actually larger than the prefixes imply.
Data-storage people, on the other hand, started out counting the bits per second they could transfer in and out, and the bits they could store, in a radio-television-telephone world where everything was counted in decimal notation, so they use exact values.
This means a mismatch between the two systems of numeration, and maybe there should be a single standard to avoid confusion, but data storage media are used for many things [e.g. audio, video] other than computer data, things which use thousands/millions/milliards of bytes as a matter of course. 1 Mbps is not 1 048 576 bits per second, and there are good reasons why it shouldn't be.


#8 of 10 Christ Reynolds

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Posted December 31 2005 - 07:31 AM

Quote:
It's hardly a scam, just a confusing use of a different system of measurement
when i buy a hard drive clearly marked 200 GB when it isn't, it's a scam. of course the fine print explains why the actual capacity is less. how can it not be a scam when the numbers differ on the same box? i dont mind the two differing notations, but people who don't (and shouldn't have to) know any better are being taken advantage of when they think they are getting a certain size drive. if it's just all confusion, why don't they just print the CORRECT number on the box? because 200 GB sounds better than 186 GB.

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#9 of 10 Christian Behrens

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Posted December 31 2005 - 05:54 PM

Plus, on CD media it IS the correct amount, i.e. a 700 MB CD will give you exactly that, 700 megabytes of storage.

Then a marketing guy had the "great" idea of inflating the numbers by using the numbers based on the decimal system instead of staying with the binary system.

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#10 of 10 Christ Reynolds

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Posted January 01 2006 - 05:47 AM

back when most CDs were 74 minutes instead of 80 like they are now, there were differing numbers as well. 650MB/680BB i believe it was.

CJ
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