I’m ripping some CDs today. I got a set of eight CDs by Bill Nelson, The Practice of Everyday Life (Amazon.com, Amazon UK). I’m using a brand new CD/DVD/Blu-Ray drive, the Pioneer BDR-XD05. (Amazon.com, Amazon UK)
The first CD started ripping at about 5x, and ended around 10x. (The first CD drives could read data at 150 kb/sec; this is 1x. Read and write speeds, for CDs, use multiples of that original speed.) Yet yesterday, I was ripping some other CDs, and they started at around 10x, finishing at 24x. Why this difference?
First, you need to know why the read speeds of optical discs changes as the process progresses. Optical discs are read from the center to the outside, and an optical drive spins at a (more or less) fixed rate. So as the laser goes from the center to the outside, the amount of data in one rotation is greater, hence the highest speed you’ll see is the very last track on an album.
But why do some discs read quickly and others slowly? This is a bit of a mystery. The only logical reason is that some discs are harder to read; that somehow, in the manufacturing process, something is done that makes a disc harder to read. Because when a CD rips slowly, you can hear the difference in the speed of the drive. Part of this may be that there are more errors on certain discs. I strongly recommend that you turn on Error Correction in iTunes, or whatever app you use to rip CDs. (Choose iTunes > Preferences, click General, then Import Settings.)
While error correction will slow down rips, it does ensure that the rips are better. These aren’t what is known as “accurate rips,” but you’re less likely to have any diginoise – pops or clicks – in CDs you rip with error correction.
In this Bill Nelson set that I ripped, the first two CDs ripped very slowly, then the third ripped at the maximum speed of my drive: around 12x at the beginning, going up to 24x at the end of the CD.
To sum up, there’s no way to find out why certain CDs rip slowly. The best guess is that they were produced in a way that makes them harder to read. You won’t notice then when playing them; the read speed is much slower. But you’ll find a vast difference between ripping speeds if you rip a lot of CDS.
Update: A friend suggested that I left something out. That the complexity of the music affects the ripping speed. That’s not the case, at least not with modern computers. Any computer sold today can compress files at much faster speeds than optical drives can rip. You can do a test. Take a lossless file from a CD, add it to iTunes, then convert it to AAC or MP3. You’ll see that iTunes compresses at 40-100x or more, depending on your processor (as long as you’re not using your CPU intensely for other software).
Here’s an example of iTunes compressing a lossless file to AAC; I had to find one long enough so I could take a screenshot, since it’s so fast: