What does "Use Error Correction" in iTunes really do?

[Ralf11]

Does it simply do several reads of a sector on the CD you are ripping?  Or does it examine a checksum first then re-scan if that doesn't match?

 

Or does it refer to an online database somewhere (Gracenote?) for checking?

 

And are there any tests of how well it checks?

[AnotherSpin]

(deleted)

[semente]

On 22 July 2017 at 7:39 PM, Ralf11 said:

Does it simply do several reads of a sector on the CD you are ripping?  Or does it examine a checksum first then re-scan if that doesn't match?

 

Or does it refer to an online database somewhere (Gracenote?) for checking?

 

And are there any tests of how well it checks?

 

Until quite recently I used iTunes to extract all my CDs (hundreds); now I use it only for rock and pop, which I seldom buy anyway, and replaced it with XLD for classical and jazz.

 

But I have used XLD to check the accuracy of a considerable amount of my iTunes rips and all were deemed accurately ripped.

Procedure is as follows:

 

1. File > Open Folder As Disc

2. At the lower lefthand corner select Verify (verification is not possible for some rips and in that case it'll read AccurateRip: NO)

3. Look for confirmation in the log file

>All tracks accurately ripped.

 

[kirkmc]

On 7/22/2017 at 7:39 PM, Ralf11 said:

Does it simply do several reads of a sector on the CD you are ripping?  Or does it examine a checksum first then re-scan if that doesn't match?

 

Or does it refer to an online database somewhere (Gracenote?) for checking?

 

And are there any tests of how well it checks?

 

I believe it simply rereads sectors where there are errors. I've found that some old or damaged CDs churn a lot when ripping them in iTunes, but I don't think it's that different from other ripping apps. There is no accurate rip database used. 

[Ralf11]

and (presumably) it determines that a sector has an error by examining the checksum?

 

or does it read each sector 2x and compare them?

 

I guess I am assuming, w/o knowing, that each sector on a Redbook CD has a checksum...

 

If it uses a sector by sector checksum, then the next question would be to what degree can errors exist but still meet the checksum...

 

just idle curiosity...   my rips sound fine (as long as I use the special beeswax filled fuses that is)

[audiventory]

Here was discussion about it https://discussions.apple.com/thread/2458631?start=0&tstart=0

[kirkmc]

I use error correction all the time, and it doesn't slow down rips. I have some discs that rip more slowly, and that's always been the case; it could be because of pressing quality. But when I get to the end of  a disc, it's being ripped at around 24x, which is the maximum speed of my drive.