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CrackedButter
Jul 17, 2003, 02:51 PM
Why does a standard blank 700MB CD once inserted into the cd drive lose 40 Megs?

Its kinda annoying because those extra megs are useful, does this happen with DVD's as well with the Apple Superdrives.

primalman
Jul 17, 2003, 03:26 PM
The space you lose is on all CDs, regardless of platform, it the file system overhead.

CrackedButter
Jul 17, 2003, 03:28 PM
Not true, on windows using Nero Burn 5, it allows you to use the whole 700MB's, i have done so myself.

acj
Jul 17, 2003, 03:31 PM
With some software you can get maybe 750, 800 megs and more than 80 minutes on a CD. They even play in regular CD players most of the time. It's called overburning.

Other software makes the cd burner actually write legible (with the naked eye) text on the outer, unburned section of a CD that's not full. Neat, huh?

thekaiser
Jul 17, 2003, 03:53 PM
Originally posted by acj
With some software you can get maybe 750, 800 megs and more than 80 minutes on a CD. They even play in regular CD players most of the time. It's called overburning.

Other software makes the cd burner actually write legible (with the naked eye) text on the outer, unburned section of a CD that's not full. Neat, huh?

Is that software to write legibly on the CD available for the mac or just the PC?

hesdeadjim
Jul 17, 2003, 03:57 PM
Originally posted by primalman
The space you lose is on all CDs, regardless of platform, it the file system overhead.

Well as I understand it, the 700 MB is actually 700,000,000 bytes and not 700 * 1,048,576 bytes (the number of bytes in a true MB). If you do the conversion, the number ends up being around 668 actual MB's which accounts for the discrepancy.

With some software you can get maybe 750, 800 megs and more than 80 minutes on a CD. They even play in regular CD players most of the time. It's called overburning.

This is true because they compress the repeated data. That is actually how you get the 80 minutes on a regular CD because one again if you do the calculations it ends up being around 75 minutes worth of data only available on the CD.

Although, I don't have a lot of knowledge beyond basics on overburning.

patrick0brien
Jul 17, 2003, 04:05 PM
It's the same limitation of audio CD's.

One isn't really supposed to exceed an hour of audio on a CD, even though you might be able to squeeze another half hour on, You see, similar to a hard drive, the CD is read from the inside out - unlike an LP.

You may have noticed that CD's aren't perfect though - they wobble, and the tracks pressed to them may not be concentric to the spindle hole. To compensate this, the laser assembly is on a magnetic suspension system to continually adjust to that wobble.

However, as the laser proceeds to the outer edge of the CD, the wobble will increase geometrically - and if one gets too close to the edge - overburning. The suspension may not have enough range of motion to compensate anymore, and you get read errors so great that the error corrector cannot function.

This is why they say 700MB or 1 hour - it's a recommendation, not a law of physics.

CrackedButter
Jul 17, 2003, 04:53 PM
Anybody here got software that allows for overburning on the mac so i can do it?