Here is an interesting
(http://www.digital-inn.de/showthread.php?s=&threadid=16313#post52038) from the EAC forum user BobHere
[QUOTE]That is a point of some discussion. There is no doubt that a correctly operating C2 error detection scheme will detect errors far more reliably than a double read system like EAC’s non C2 secure mode. The issue is how good is the C2 reporting of the drives.
Almost all testing I have seen on C2 reporting has been under extreme circumstances (long black mark tests). The performance of C2 reporting revealed by these extreme tests may be affected by a number of factors that may have nothing to do with its own accuracy and more to do with how the drive responds to such extreme conditions. Most everyone would abandon a rip that had this level of damage.
The LTR40125s gives very good (almost perfect) C2 reporting even with these extreme tests. I have previously done some extensive testing of C2 and I am satisfied that it works perfectly on all three of my drives under normal conditions. In the absence of definitive test results the final decision is up to you.
Here is another
[QUOTE]The behaviour around a large black mark is difficult to describe without knowing how the chipset has been designed, these things are not laid down in stone in the Red Book standards. It will probably deviate from what is predicted by CIRC and it may be this that is causing some drives to test poorly to C2 reporting using Andre’s test disc.
These are some questions that need answers to get a 100% understanding and be the God of DAE!
Does the drive mute?
If it mutes what is the trigger point to start and end a mute?
If it mutes, what algorithm does it use to prevent a click at the mute and demute points?
Does it have advanced interpolation and how does this work?
How does the drive resynch after a loss of synch? How many frame headers does it check, does it ‘backtrack’ after meeting its resych criteria (may relate to your question)?
Does the drive flag bad EFM symbols and mark them as erasures for the C1 decoder or does it pick the most likely answer and just hope.
What does the drive do with the data stream when it gets a HF optical output dropout (caused by the loss of return signal), does it act on this information to mark the data as erasures or pass it along as zeros or pass along bad data (at least at the transistion point)? At the transistion point does it mark individual symbols as erasures or does it mark the whole frame ( this may relate to a question you have asked about the beginning of the black mark). This dropout can also be detected in CIRC as both the audio data and parity data would be zeros which is not allowed in normal operation of the code (the parity symbols are inverted), I don’t know whether this behaviour is specificed in Red Book.
There are probably many more.
So many possible combinations.
This all sound very plausible to me. A lot of factors are mentioned which might confuse the outcome of the DAE quality test…
For more info on technical issues concerning audio cds search for the posts of BobHere or Pio2001