CD Speed - Can anyone explain what it means?



Whilst I of course, understand that when you look at a CD speed graph (I’m talking the “disk quality test”

The less and lower the bottom GREEN and upper BLUE bars are, the better.

But what do they actually mean, and how much means it’s getting towards the point where is may not be reliable.

Take this scan for example:

On the bottom,I have green with some yellow up to 3

On the top I have blue up to around the 200 mark.

I also have a curved green line on the top chart as well (no idea what that is)

The lines on the lower chart change colour the higher they go (why is that)
If there is a spike (say up to 10) on the bottom it goes to red, or ever purple if higher.

I’m not even really sure what PI Errors and PI failures mean.
What’s better and error or a failure?

Just some basic background on the meaning of all of this would be appreciated.

Many thanks


First of all, DVDROM drives are not suitable for scanning. The results cannot be guaranteed, neither can the speed of the drive of be controlled properly.

On all DVDWRITERS, any results with PI (the top graph) under 280 is satisfactory. Excellent discs stay under 40.
On a liteon DVDWRITER, anything under PIF (the bottom graph) of 4 satisfies DVD standard. Excellent discs stay under 2.

PI errors are usually errors which are correctable by the drive using the DVD formats designed PI error correction. PIF’s are errors which the drive cannot correct & passes back to the OS to deal with.


Not quite.

There are two stages of error correction for DVD media, Parity Inner (PI) and Parity Outer (PO).

PIF ae Parity Inner Errors (PIE) that cannot be corrected by the PI stage of error correction, so they are marked as Parity Inner Failures. They are then passed on to the Parity Outer error correction layer and in most cases will be corrected there. Only if they also fail PO error correction will an actual error signalled to the operating system occur. Depending on the drive and and depending on how the application or operating system is reading the disc, the drive might attempt to re-read the failed sector(s) from the disc before signalling a failure.


Many thanks for the two replies.

Still not sure if CDSpeed is actually showing everything you need to know.
(Where are the Parity Outer errors?)

going to order my LiteOn drive this week, so will have more reliable scans to post in the future :slight_smile:


That is actually much more complex than you realize.

The short answer is that a high-speed scan (16x or 12x depending on drive) combined with a Read Transfer test is usually enough to know if a disc is good.

A medium/low speed scan combined with a Read Transfer test is the next best method IMO, but the drives used for testing should be chosen carefully.

(Where are the Parity Outer errors
Only a few drives can show this: BenQ DW1620…1655 and DW8xx drives with the Advanced Disc Quality scan feature in CDSpeed and later, and Plextor PX-760/755/716/712 drives with PlexTools Burst scanning.


Again, thanks for the reply.

Just wondering if it’s common practice to scan EVERY disc you burn.


I guess that different people do it differently.

I personally scan every disc I burn at 16x speed in my LiteOn 165P6S drive. The disc is also verified in the drive that burned it, so that I know it can be read and that the data is not corrupted.

Some people only scan a couple of discs from each cakebox they open.

Most people are not CDFreaks and don’t scan at all.


I do. Is it “common practice”? Don’t know, but I scan and document the results for each burn…over 1,000 now.


The green line is the speed of the drive-starts at 2X and continually gets higher as you read more of the disc