Can Only Read Certain Discs

Question

I don't use discs very often, but recently I noticed that my macbook pro is unable to read a lot of my discs. The machine will accept the disc, whirr for a while, then eject it without seeming to recognize it. This is especially confusing as I know it was able to read some of these specific discs last year.
After some experimentation I realized that the discs that DO work seem to have some of the center area filled in with extra data storage. After looking up the fact that the data on a disc starts at the center, the issue becomes clear: the machine tries to start reading at this smaller diameter and gives up without checking further out.
Is my optical drive broken or is this a problem with the OS?

Answer 1

Aidinthel wrote:
I don't use discs very often, but recently I noticed that my macbook pro is unable to read a lot of my discs. The machine will accept the disc, whirr for a while, then eject it without seeming to recognize it. This is especially confusing as I know it was able to read some of these specific discs last year.
After some experimentation I realized that the discs that DO work seem to have some of the center area filled in with extra data storage.
There is no "extra data storage". It's just a label.
Basically, your drive detects disc insertion, attempts to read the disc, and doesn't get a useful result. It concludes that the disc is damaged or incompatible and it spits it out. Assuming that these discs are clean and undamaged (that includes the label side), here's what could be going on
(1) With age, the drive's laser beam can no longer focus very tightly. It can still read some discs, but fails with others. Unfortunately, you cannot check this unless you're technically inclined and have an oscilloscope. If your drive is 5 years or older, this is a distinct possibility.
(2) Dust or other particles can settle on the drive's lens; this scatters the laser beam, with the same effect as in (1). You cannot check this with the naked eye, but you can try to fix it. There are special cleaning discs designed for this purpose. I cannot recommend any brand or model, but you can find them in them in the usual places (electronics stores, Amazon, etc). Make sure to read reviews of other users before buying and using such a disc.
(3) Manufactured optical discs usually have a metal reflecting layer. When correctly manufactured, such a disc lasts a long time. But recordable media (CD-R, DVD-R, DVD+R, etc) employ a dye, which, even when new, has less contrast between 'pits' and 'lands'. In time, this contrast fades even more, so eventually the disc becomes unreadable and the data is lost. There can be considerable variation in the durability of recordable media. Some cheap, low quality discs can become unreadable even within a year.
So, first check your media. Are the unreadable discs factory-made or recordable media? If the drive has problems with factory-made discs, first, make sure that the discs are good (other drives can read them); if they are, try cleaning your drive. If cleaning your drive hasn't worked, then it may be time to replace it with a new drive.