EAC secure mode test proposal
Reply #33 – 2003-06-05 00:11:14
Tigre, it seems what you call extended reread is assuming that all errors in the rereading range are detected. You're right. I just tried to find the errors that will remain undetected for sure ...One should rip 16 different versions of the CD, and keep the samples that are 8 or 9 times the same as good, then see if they actually are. ... because I'm too lazy to rip 16 more times - and do 15+ more comparisons. You're right: One should ... - but this "one" won't be me. In this case, your 99.8 and 97.4 % results are just upper bounds for the actual accuracy, because among the 1930 and 86 other errors, many will remain undetected after rereading, since they are consistent. The 80 % accuracy is then not unlikely. Hard to tell without testing. I'd rather think that most of the errors are detected during 1st 16 re-reads (because of reduced speed and the finding I mentioned in the post before: in secure mode (C2 off, Drive caches checked) the same drive + same CD either give perfect results or report errors at bad positions - 10 trials, no undetected error).These consistent errors would be just samples damaged beyond recovery. Each time they are read, an error occurs, and they are always interpolated, thus returning a consistent result. The way I understand how audio CDs work, there's quite some damage necessary to get an unrecoverable error (C1 + C2 failing). So as several damaged = "unsecure" bits read in raw data are needed to cause an error (that makes the drive interpolate), it's rather unlikely that all of these bits are returned identically on several re-reads resulting in identical interpolation. Whatever ... My conlusions so far: - More tests needed - Real life secure mode performs much better on error detection than my "simulation" for so far unknown reasons. - It seems like Secure mode (C2 off, correct cache settings) is more secure in error detecting than Burst mode Test & Copy with CRC check.