another superdrive question

[brentg33]

ok, so a few days ago i took my 2 1.2 year old MBP to the genius bar and had the superdrive replaced. So today is the first day i am trying to burn a .iso to dvd. I am using toast and initally it started at 6x i believe. about 1/2 way through burning is slowed to a crawl to about 2x or 3x. .... is this normal? the iso was stored on my external HD connected via FW800. It seems to have burned a working disc however.

thanks

 

[NewMacbookPlz]

I wouldn't call it normal, but I have had that happen before while burning a DVD+R disc...only 1 out of 10-12 I've recently burned. Maybe it's the drive auto-sensing the disc speed as it can when you insert the disc, and slowing down due to something with the optical material as the disc goes?

 

[spinnerlys]

The speed has to get slower, as the burning process begins at the beginning of a disc, which is nearest to the CD/DVD. As the burning process progress the laser has to move away from the center. If the superdrive would burn the outer regions of CD/DVD with the same (faster) speed as the inner region, the spinning could cause damage.

 

[NewMacbookPlz]

The speed has to get slower, as the burning process begins at the beginning of a disc, which is nearest to the CD/DVD. As the burning process progress the laser has to move away from the center. If the superdrive would burn the outer regions of CD/DVD with the same (faster) speed as the inner region, the spinning could cause damage.

I thought it was the opposite. The disc rotational speed is fixed at whatever #x value. As you reach the outside of the disc, that portion is moving faster rotationally and in more data is written in a given amount of time.

 

[spinnerlys]

I thought it was the opposite. The disc rotational speed is fixed at whatever #x value. As you reach the outside of the disc, that portion is moving faster rotationally and in more data is written in a given amount of time.

You might be right.

It's late and I myself find it confusing right now. Will check back later.


But to that slower burning issue, I have experienced the same with many DVD writers in Mac Pros or iMacs or MB(P)s.


EDIT:
DVDs hold seven times more information and spin three times faster than a CD. The rotational speed, or angular velocity, of a DVD goes between 570-1600 rpm (rotations per minute). The closer to the center of the disc, the faster it spins and which is why there is a range for the angular velocity and not one specific number. This means the "read head" passes the same length at all times and radii. Theconstant linear velocity (CLV) is why a DVD spins slower on the outer edge and faster on the inner edge.

from http://hypertextbook.com/facts/2003/ClerbieMontilus.shtml

or

DVD players also usually read discs at a constant linear rate. The disc's rotational speed varies from 1530 r/min (actually 25.5 Hz), when reading at the innermost edge, and 630 r/min (actually 10.5 Hz) at the outer edge.[1] DVD drives’ speeds are usually given in multiples of this figure.

from http://en.wikipedia.org/wiki/Revolutions_per_minute