On Sat, 18 Feb 2017 14:21:48 +0000, Eiron
wrote:

On 18/02/2017 12:00, Iain Churches wrote:
"Vir Campestris" wrote in message
o.uk...
On 17/02/2017 09:42, Iain Churches wrote:
A bad pressing? I like that :-))

I did have one once. It so happened we had a CD tester at work, and it
showed multiple errors scattered all over the surface. I contacted the
manufacturer, and they sent me a new disc. Pressed somewhere else... I
don't know if they did anything with the tester report I sent them.

:-))

Did the multiple errors affect the replay, or prevent
the disc from playing? Quite often they do not.

CD plants produce in "lines", so the replacement disc does
not have to be made somewhere else just on a different line.

A Reed Solomon reader (probably like the one you had at
work) is used for QC. One of these two gentlemen
(Reed or Solomon) is quoted as saying "without error
correcting codes digital audio would not be technically
feasible"

Which is complete bollox.

Anyway, a CD will play perfectly even after drilling a few 2mm holes in it.

Yup, and the reason it will is the error correction, specifically
trellis coding that splits a byte up into individual bits then dots
them all over the place so something like a hole won't destroy
complete bytes which would be hard to rebuild. The R&S coding plus a
heap of redundancy means you can reassemble valid data from some
pretty awful damage. They are right that not many CDs would survive
more than a few plays and still be readable without this error
correction.

d

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus