( technical background for this discussion =
http://www.ee.washington.edu/consele...udio2/95x7.htm )
I always though that there was no interpolation nor muting, and that the noise that was decoded as a symbol (thus leading to error detection) was outputted raw.
And this idea was backuped by the fact that my Yamaha standalone player always plays perfectly without any audible clicks some CDRs that are so damaged that CD ROM drives are muting big parts of the waveform.
My undestanding was that muting always leading to a null sample, reading twice would output two null samples, therefore no error detected, and that interpolation occuring necessarily between two valid samples, and valid samples being error free, interpolating twice between the same samples would lead to twice the same output, so no error detected either.
Quote:
Originally posted by Andre Wiethoff
The basic of EACs secure mode without C2 is that on errors the probabilty of twice an extraction is the same is low (having twice exactly the same errors)...
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I never though about it.
But after all why not...
So instead of saying "an error never returns twice the same data", we say, "any error always returns the same data, but they never occur twice at the same place" right ?
If we look at how the data is descrambled :
Having a C2 error means having at least 4 or 5 bad symbols in a C2 block, so reading problems must run for 13 or 17 CD blocks at least.
But having isolated clicks in the digital output means to have a bad C2 block and a good one two blocks later. Since the data two blocks later comes from CD blocks in the same aera as the ones of the bad C2 block (the blank ones between, in the picture), we can assume that the aera is not completely damaged, but that the eror rate is just becoming rather high in this aera, with random read errors here and there, leading from time to time to 4 or 5 bad symbols in a C2 block.
EAC checks for differences in 27 sectors each time, thus 27*588/6=2646 blocks at once.
This seems plausible. It must be efficient even if an error always return the same data (interpolation or muting)
This way, is the secure mode more secure than the paranoid mode ? The probability to get twice the same errors in a sector (98 blocks) must be higher than in 2646 blocks, isn't it ?
I'm running a test with a special CD, that should settle the interpolation question for my drives, I've still to record twice or thrice the whole CD realtime, then edit the wav, then run the analyse.exe on it. Interpolation should drastically reduce the difference level on this CD, that is a old dying CDR. Leave me some days to go on