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Using BLER to determine audio quality of CDs?

No sure if this post goes under Music or Digital, but here goes.

Has anyone used a CD/DVD RAM disc scanner to get block error rate (BLER) data of their audio discs? I was doing some ripping of my audio CDs and I have a software utility for my Plextor CDROM drive that lets me scan CD/DVDs for BLER errors. It reports both C1 and C2 error rates. Usually, this is used to check burned CDs and DVDs for errors, but I though I would try it on my commercially produced audio CDs.

I have some older discs from the early 80s, and was shocked to find some very high error rates. For example, an early 80s American production of Pink Floyd Dark Side of the Moon produced C1 AND C2 error rates in the thousands! The Rebook spec is MAX 220 for C1. Animals and Wish You Were Here were equally as bad.

Maybe this is evidence of "CD rot", although I have old Polygram German pressings (Camel Snow Goose, Moonmadness) of the early 80's that show C1 error rates of Max 20, and zero C2. Also, my Johm Klemmer Touch cd (early 80's) shows C1 rates of about 25 max, no C2 errors, and its an MCA release.

Thought this might be a good method for checking the older CDs for increased errors, or even for new pressings to weed out potentially bad sounding CDs.
dhl93449
tpreaves's avatar
tpreaves
2,688 posts
 
Are these numbers just something that you are curious about? A recording either sounds good to you or it doesn't. You can crunch numbers all day long but the outcome is still the same.
ghosthouse's avatar
ghosthouse
4,335 posts
 
Dhl - interesting stuff. Thanks for sharing.
dhl93449 OP
455 posts
 
Well, here is an update. As with a number of things, a measurement may not always be the measurement you think it is...

I am curious about the numbers as a potential screening method, particularly since I have a large number of 80's era production CDs, and I suspect some of them may be degrading audibly. So they might go on a potential "replacment" list if they have a lot of errors. I am also curious to see if a method to actually measure "CD rot" can be found this way.

But to get back to the measurement. I have now found that the BLER error rates are measurement speed dependent. If measured at 48X, I will get a large number of errors (thousands of both C1/C2 errors). Freaked me out when I found this on a recently obtained MFSL CD. But slowing down the measurement read speed to 4X (the lowest it will go), produced C1 errors on the same MFSL disc in the single digits or low teens, with 0 C2 errors. Now that is more like it. Since CD players run at 1X, error rates may be even lower.

This begs the question re the new players that use cheap computer CDROM drives and "read ahead" for data, storing it in a buffer for playback. Yes, they have read/re-read error correction circuitry but do you really want this circuitry running on errors that might not actually be there(as real physical defects) if the drive speed is low? IE false errors generated just due to read speed?
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