DVD Math

[shindawa]

I recently installed a 18x DVD burner. I am happy with it and it can burn a DVD in less than 6 minutes.

However, I was wondering about the 18x burn speed. My CD burner is 48x and takes around 3 minutes to burn 500mb. If burning 500mb at 48x takes 3 minutes, shouldn't 4 gigs at 18x take over an hour?

I'm not complaining, I'm just looking for an explaination.

Thanks

 

[choirbass]

well, the main difference is in the amount of data that can be read/written between the different standards at a given multiplier...

1x cd speed = 150 KB/s

1x dvd speed = 1353 KB/s

1x dvd speed = ~9x cd speed

18x dvd speed = 24354 KB/s

48x cd speed = 7200 KB/s

...technically if your 18x dvd burner could burn cds at that same speed, it would be a 162x cd burner, lol

now, i may have done that math wrong, but the initial dvd and cd multiplier speeds are correct

hope this helps

 

[joex444]

I have to agree, you can't equate DVD and CD speeds.

For both, they represent the maximum data stream in their original application, the Audio CD (PCM WAVE 1411kbps) and DVD Video (maximum of around 10Mbps).

 

[shindawa]

Thanks for the reply. I now understand why the DVD burns so quickly:

1x cd speed = 150 KB/s
1x dvd speed = 1353 KB/s

Does that mean when you watch a DVD at normal speed, 1353 KB/s are being transfered?

If an 18x DVD burner can transfer 24354 KB/s, then why can't it burn CDs at 162x? (I understand there is no 162x blank media)

 

[choirbass]

that... i dont know why, lol... but, it 'could' very well be for that exact reason, that the media being written to doesnt support that high of a read/write rate... otherwise, you 'probably' would be getting reads and writes at that speed, since the optical drive is very much capable of it... im just guessing about that though, i would speculate though that the media being used is the limitation there

and yep... if youre reading a dvd at 1x, its transferring at 1353KB/s, and so on and so forth

 

[jt001]

If an 18x DVD burner can transfer 24354 KB/s, then why can't it burn CDs at 162x? (I understand there is no 162x blank media)

Because since a DVD has the data packed more densely than a cd it can read more while still spinning the disc at roughly the same RPM. If you were to spin the disc any faster it would likely shatter(which is already an issue with old cd-rom's in fast drives)

 

[skittle]

why cant it burn at 162x?

Because the CD drive cant spin that fast, the CD would prob shatter inside the drive.

 

[commanderspockep]

If an 18x DVD burner can transfer 24354 KB/s, then why can't it burn CDs at 162x? (I understand there is no 162x blank media)

Basically DVDs are encoded in a different format and at a much higher density. In other words you can cram more data into the same amount of space. This means you can record more data on a DVD disc without the disc having to spin at a faster speed than a CD would. The max that they have achieved for a CD is 52x. It's just not possible to achieve 162x, it would be very very difficult to get a drive to spin that fast. Even if they could get a drive that would spin that fast the CD itself would break up because of the heat.

Also its important to note the laser to read and write a DVD is smaller than a CD laser. This allows the DVD laser to focus on the smaller "pits" on a DVD.